From nobody Mon Sep 16 20:23:42 2024 Received: from mail-yw1-f201.google.com (mail-yw1-f201.google.com [209.85.128.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 1B2C613B784 for ; Thu, 15 Feb 2024 18:28:10 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708021692; cv=none; b=V5AtTFOZRJKzzJcFsF+8fDa+DsjznhairWZS3HUm2ug0zlysDX01cquHlnVM5Ma78NJ7l3tMr1A8d+vYKf8ljGhHShZoYmQ1pjEOxMsTT5eiMOCpoak650he3JNGb1K9Qwth1mDry67mo1gg18uA6awbg8M8eJS03+VDbwhd2E4= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708021692; c=relaxed/simple; bh=APdeBRsHAtrJONBAc4fOC4nb+0sbyGbwGk53lr6VS2s=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=A4Yxo+le9A75RHq0pcryW/nbxuPtYwQHleXf6sfXTMtCndxLEOF0uxIfHRTrJy0VEAeTK+jiCW0RUY0LooE+sYMsLB7kuhJrUVXtqWvXJZveSGobrsgYdrJNpdZb4A2BltttxHebSmoGpsDIlV7daLqBkYmsK2+1zqL82uG7JpE= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--lokeshgidra.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=JdeZASRb; arc=none smtp.client-ip=209.85.128.201 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--lokeshgidra.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="JdeZASRb" Received: by mail-yw1-f201.google.com with SMTP id 00721157ae682-607e56f7200so5668257b3.2 for ; Thu, 15 Feb 2024 10:28:10 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1708021690; x=1708626490; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=5jFzOipv9bDJZnpb7UwZ8Eham/ShclgiDNDH7Ow4z+0=; b=JdeZASRbYGYpemdfvKlLncp+bu5y5SrC9zBhw3hUislOcnKDtb8Maj+MENxMnDBGz8 +3+LGzuHYoaPV80kNhyGPR6dW+5DIgB174pmMlT50p+5WRL2ss/TbnVO3KmYW4UGLC1C Pc3y7YAVoZuz8OXIY6UpTFVcJAtbc9PRkn7gWSmEUBpN6BZWyb0PEdX/dMmEFEZUJSlD WPnKXbD+FKcDG8HqwxgEm1RLg4m1NuD7NMH459wax33b81DplHbFcTxGtOdGCxRHeKky JR8swyaRs+ap5hHtKe+Js63RVYTgDPAxkQn0Bgt0gSmpb4GXwd3VnhB1WqxM2VvDwnO0 QbGw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1708021690; x=1708626490; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=5jFzOipv9bDJZnpb7UwZ8Eham/ShclgiDNDH7Ow4z+0=; b=fgwo8Ao04d18Jve2bZ3PbdCyfJqYNML+WGDSZ82t7axkPue/miI8/hgivrGsYKMhFm 11dHMpVxQdljfg35RNtnMBtJ66SNSfK36rxN63UX6rDSCPynde6jVBXZ310xuIiQnegQ 0xORtjOo4KXvxZz3M/kziKJxJHbnmHnqEr1Y4EdnRsA9cP7FROawdnL/4N0frj33ABG/ Ma4seYSZi8281bWxfKRs7yqQF+fqbqcecoOaG86cYqPUIredTwHyIH4EOrz0j5gS7rPO ZkourNeXSVBdkrTHzKJ3ugvF1lUOdWBZa5Qdg1olUWnPOlyv+U7QR55RBsF38fCE6dRH SWog== X-Forwarded-Encrypted: i=1; AJvYcCXnqqJ9DgedqiUP0P/kQURmzgefYhwssq88LJsF0+BYdRh2prvno+Cl+m9gAghZJPLhRwaOKWxSbJDqd7SW5P3DE+O4+99FSW5NKNQ3 X-Gm-Message-State: AOJu0YxMhsCmo34ejy1Xt3Rbrlg6HEp1E4d4KZuozclkynbfkkBGzas/ /iOTQjuotLy6mSXfJpiZcDlHrZzlzTa0rFo5ZIra045BGgBq5yGLO5Twdh46s9ObuQszJpLrvpg oRDJzuv79c996BBQM5tIDyw== X-Google-Smtp-Source: AGHT+IHHi2mCkEldISrNhtoRZCLnocCFS9qBcw8e+39nrcye3IQvcjCcfdDQNRvMWp/R1wX/qkVergX2FymdVGvJXg== X-Received: from lg.mtv.corp.google.com ([2620:15c:211:202:6186:87a3:6b94:9b81]) (user=lokeshgidra job=sendgmr) by 2002:a05:6902:f11:b0:dc6:db9b:7a6d with SMTP id et17-20020a0569020f1100b00dc6db9b7a6dmr83663ybb.13.1708021690138; Thu, 15 Feb 2024 10:28:10 -0800 (PST) Date: Thu, 15 Feb 2024 10:27:53 -0800 In-Reply-To: <20240215182756.3448972-1-lokeshgidra@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20240215182756.3448972-1-lokeshgidra@google.com> X-Mailer: git-send-email 2.43.0.687.g38aa6559b0-goog Message-ID: <20240215182756.3448972-2-lokeshgidra@google.com> Subject: [PATCH v7 1/4] userfaultfd: move userfaultfd_ctx struct to header file From: Lokesh Gidra To: akpm@linux-foundation.org Cc: lokeshgidra@google.com, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, selinux@vger.kernel.org, surenb@google.com, kernel-team@android.com, aarcange@redhat.com, peterx@redhat.com, david@redhat.com, axelrasmussen@google.com, bgeffon@google.com, willy@infradead.org, jannh@google.com, kaleshsingh@google.com, ngeoffray@google.com, timmurray@google.com, rppt@kernel.org, Liam.Howlett@oracle.com, ryan.roberts@arm.com Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Moving the struct to userfaultfd_k.h to be accessible from mm/userfaultfd.c. There are no other changes in the struct. This is required to prepare for using per-vma locks in userfaultfd operations. Signed-off-by: Lokesh Gidra Reviewed-by: Mike Rapoport (IBM) Reviewed-by: Liam R. Howlett --- fs/userfaultfd.c | 39 ----------------------------------- include/linux/userfaultfd_k.h | 39 +++++++++++++++++++++++++++++++++++ 2 files changed, 39 insertions(+), 39 deletions(-) diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c index 05c8e8a05427..58331b83d648 100644 --- a/fs/userfaultfd.c +++ b/fs/userfaultfd.c @@ -50,45 +50,6 @@ static struct ctl_table vm_userfaultfd_table[] =3D { =20 static struct kmem_cache *userfaultfd_ctx_cachep __ro_after_init; =20 -/* - * Start with fault_pending_wqh and fault_wqh so they're more likely - * to be in the same cacheline. - * - * Locking order: - * fd_wqh.lock - * fault_pending_wqh.lock - * fault_wqh.lock - * event_wqh.lock - * - * To avoid deadlocks, IRQs must be disabled when taking any of the above = locks, - * since fd_wqh.lock is taken by aio_poll() while it's holding a lock that= 's - * also taken in IRQ context. - */ -struct userfaultfd_ctx { - /* waitqueue head for the pending (i.e. not read) userfaults */ - wait_queue_head_t fault_pending_wqh; - /* waitqueue head for the userfaults */ - wait_queue_head_t fault_wqh; - /* waitqueue head for the pseudo fd to wakeup poll/read */ - wait_queue_head_t fd_wqh; - /* waitqueue head for events */ - wait_queue_head_t event_wqh; - /* a refile sequence protected by fault_pending_wqh lock */ - seqcount_spinlock_t refile_seq; - /* pseudo fd refcounting */ - refcount_t refcount; - /* userfaultfd syscall flags */ - unsigned int flags; - /* features requested from the userspace */ - unsigned int features; - /* released */ - bool released; - /* memory mappings are changing because of non-cooperative event */ - atomic_t mmap_changing; - /* mm with one ore more vmas attached to this userfaultfd_ctx */ - struct mm_struct *mm; -}; - struct userfaultfd_fork_ctx { struct userfaultfd_ctx *orig; struct userfaultfd_ctx *new; diff --git a/include/linux/userfaultfd_k.h b/include/linux/userfaultfd_k.h index e4056547fbe6..691d928ee864 100644 --- a/include/linux/userfaultfd_k.h +++ b/include/linux/userfaultfd_k.h @@ -36,6 +36,45 @@ #define UFFD_SHARED_FCNTL_FLAGS (O_CLOEXEC | O_NONBLOCK) #define UFFD_FLAGS_SET (EFD_SHARED_FCNTL_FLAGS) =20 +/* + * Start with fault_pending_wqh and fault_wqh so they're more likely + * to be in the same cacheline. + * + * Locking order: + * fd_wqh.lock + * fault_pending_wqh.lock + * fault_wqh.lock + * event_wqh.lock + * + * To avoid deadlocks, IRQs must be disabled when taking any of the above = locks, + * since fd_wqh.lock is taken by aio_poll() while it's holding a lock that= 's + * also taken in IRQ context. + */ +struct userfaultfd_ctx { + /* waitqueue head for the pending (i.e. not read) userfaults */ + wait_queue_head_t fault_pending_wqh; + /* waitqueue head for the userfaults */ + wait_queue_head_t fault_wqh; + /* waitqueue head for the pseudo fd to wakeup poll/read */ + wait_queue_head_t fd_wqh; + /* waitqueue head for events */ + wait_queue_head_t event_wqh; + /* a refile sequence protected by fault_pending_wqh lock */ + seqcount_spinlock_t refile_seq; + /* pseudo fd refcounting */ + refcount_t refcount; + /* userfaultfd syscall flags */ + unsigned int flags; + /* features requested from the userspace */ + unsigned int features; + /* released */ + bool released; + /* memory mappings are changing because of non-cooperative event */ + atomic_t mmap_changing; + /* mm with one ore more vmas attached to this userfaultfd_ctx */ + struct mm_struct *mm; +}; + extern vm_fault_t handle_userfault(struct vm_fault *vmf, unsigned long rea= son); =20 /* A combined operation mode + behavior flags. */ --=20 2.43.0.687.g38aa6559b0-goog From nobody Mon Sep 16 20:23:42 2024 Received: from mail-yw1-f201.google.com (mail-yw1-f201.google.com [209.85.128.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 5046C1474CB for ; Thu, 15 Feb 2024 18:28:13 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708021695; cv=none; b=drFu6L7uzzM5D8m8rWXtXuNbbvqp0Hr7f5HXlCXdf/G91MgX08DwdAsPEAX1uBkN2MWtVQ3WfrVNAKdzG531eURds4GuTWwrn+M3cDnKu2l7BFUd1BRvsYBYZlFsDyZTs/ZgWGGmrufvQliHEAJJH/p7kl7Zc6JqNL9ZAIf7F+0= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708021695; c=relaxed/simple; bh=ihOSsK0nLit+j5KPpPeO7ZcBdi8bIDQ4zpivLgeROSc=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=GaeoVzEoWb+rdtScJdOTslYQtxAsUIh258y/49Anup+DPXxllkQXswC6/4VNJ5JUXiGUKW/tKb6wjDAdZQI4S+/MmVDXXuS1temuM2DIQEVCC/ZRy4sAZiXJ27KMkHG2MiaxMoMUbsl4f+hXEpqIsGXS+AkXgLTXjuUE4o6df8o= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--lokeshgidra.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=ClKYHeNs; arc=none smtp.client-ip=209.85.128.201 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--lokeshgidra.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="ClKYHeNs" Received: by mail-yw1-f201.google.com with SMTP id 00721157ae682-607d4faaca4so13108937b3.3 for ; Thu, 15 Feb 2024 10:28:13 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1708021692; x=1708626492; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=Fcctbu40uMom0FYs5iKpq/6WlwkN62DCYz1tSKTG8lI=; b=ClKYHeNsSaGYeUeYhboak7OlKb9VGkOnmBjlhGQ5hZt7ehoPn/EOtX4f2wOXcuzk0B 9Ga2tJ6GTH9w5/5bmKqKdd0IoDTLRVjh9sPdmvxv5cj/jCi8fF3RTsK+52WJhf7mbrUG dAqd8t4ATVfmyc75AyG97qXFSeNKJTTbnQYBelUfubFkKr7qLK1flwHYveuGnuS5QZFw ZOI+tC4s16A9mxdwhz0iLmli8AeE1qjK2F/YXOayoSKs3liox/HwsWf9Av4yID9ql8l/ 1DGCa1OvYk8RfWasY/fnTN1W+BNu5l5Cn+PzXreqsuQybYSWgdRMycPcJcqnkx3KNC3S kCEQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1708021692; x=1708626492; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=Fcctbu40uMom0FYs5iKpq/6WlwkN62DCYz1tSKTG8lI=; b=rx97x4L9RXIU4tg7zSsBF+15gWlP5m0HKYHdzhpQsaG60Ct/pc50FI/pn9XLUeDMdt eYi5PVEXYV53KTErTxfWR4hjFK8MKStnO4xG23D4WyVxNc5dFK2WyD86cBJ83nD2CVJ7 RW0tjE0LfxrERwMoc2THL/fGEItQWwVfj172jDGzY6rGvIiXUvVgRKsGo3jvCwNpE0Yu +bo6hbnH9tx9mbiWhhavN6l+cBJAhymFGTi0G2sR76j/KK8X0zU/r3FjMTDMqIgq4K5J 8mxezgb/zJNdIzYA9InJKzPC7CXP35NRJmQwKK+6rKMuBeMbooXjnFWerwBuSULLMFPk CZHQ== X-Forwarded-Encrypted: i=1; AJvYcCXKLYGVVJQRAk6DT9jGT8zxpG8JsC6ae12mLziMIY1CvVSK/+Z75+28Va181IMpvpoYeoo2s3PQTkU5+O+JpeZ+4AlgkcirABMwMGQd X-Gm-Message-State: AOJu0YxVjv1Vejyv9Tv6a71JG2WPddgYqlubbMNZGHimP9FNk1KTG/AU bqpGG40R/bnCAINMsvlZir5BjTywAlmRkNEW95FDOKqXBmWkv1VjTLS0MHSu38S+Z3KCds43xZ1 U1lcHGuF8dttbMvAV0UcRuQ== X-Google-Smtp-Source: AGHT+IF9VE8A2Eb1+apIi+s8kSWn55FpfbHwy7Dntox5xt8VbrK7eDxZpoiuJ8Ap3aW9CEwVJJ8SnUyVfI1bXY6XFw== X-Received: from lg.mtv.corp.google.com ([2620:15c:211:202:6186:87a3:6b94:9b81]) (user=lokeshgidra job=sendgmr) by 2002:a81:5748:0:b0:607:c418:33ba with SMTP id l69-20020a815748000000b00607c41833bamr590841ywb.8.1708021692378; Thu, 15 Feb 2024 10:28:12 -0800 (PST) Date: Thu, 15 Feb 2024 10:27:54 -0800 In-Reply-To: <20240215182756.3448972-1-lokeshgidra@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20240215182756.3448972-1-lokeshgidra@google.com> X-Mailer: git-send-email 2.43.0.687.g38aa6559b0-goog Message-ID: <20240215182756.3448972-3-lokeshgidra@google.com> Subject: [PATCH v7 2/4] userfaultfd: protect mmap_changing with rw_sem in userfaulfd_ctx From: Lokesh Gidra To: akpm@linux-foundation.org Cc: lokeshgidra@google.com, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, selinux@vger.kernel.org, surenb@google.com, kernel-team@android.com, aarcange@redhat.com, peterx@redhat.com, david@redhat.com, axelrasmussen@google.com, bgeffon@google.com, willy@infradead.org, jannh@google.com, kaleshsingh@google.com, ngeoffray@google.com, timmurray@google.com, rppt@kernel.org, Liam.Howlett@oracle.com, ryan.roberts@arm.com Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Increments and loads to mmap_changing are always in mmap_lock critical section. This ensures that if userspace requests event notification for non-cooperative operations (e.g. mremap), userfaultfd operations don't occur concurrently. This can be achieved by using a separate read-write semaphore in userfaultfd_ctx such that increments are done in write-mode and loads in read-mode, thereby eliminating the dependency on mmap_lock for this purpose. This is a preparatory step before we replace mmap_lock usage with per-vma locks in fill/move ioctls. Signed-off-by: Lokesh Gidra Reviewed-by: Mike Rapoport (IBM) Reviewed-by: Liam R. Howlett --- fs/userfaultfd.c | 40 ++++++++++++---------- include/linux/userfaultfd_k.h | 31 ++++++++++-------- mm/userfaultfd.c | 62 ++++++++++++++++++++--------------- 3 files changed, 75 insertions(+), 58 deletions(-) diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c index 58331b83d648..c00a021bcce4 100644 --- a/fs/userfaultfd.c +++ b/fs/userfaultfd.c @@ -685,12 +685,15 @@ int dup_userfaultfd(struct vm_area_struct *vma, struc= t list_head *fcs) ctx->flags =3D octx->flags; ctx->features =3D octx->features; ctx->released =3D false; + init_rwsem(&ctx->map_changing_lock); atomic_set(&ctx->mmap_changing, 0); ctx->mm =3D vma->vm_mm; mmgrab(ctx->mm); =20 userfaultfd_ctx_get(octx); + down_write(&octx->map_changing_lock); atomic_inc(&octx->mmap_changing); + up_write(&octx->map_changing_lock); fctx->orig =3D octx; fctx->new =3D ctx; list_add_tail(&fctx->list, fcs); @@ -737,7 +740,9 @@ void mremap_userfaultfd_prep(struct vm_area_struct *vma, if (ctx->features & UFFD_FEATURE_EVENT_REMAP) { vm_ctx->ctx =3D ctx; userfaultfd_ctx_get(ctx); + down_write(&ctx->map_changing_lock); atomic_inc(&ctx->mmap_changing); + up_write(&ctx->map_changing_lock); } else { /* Drop uffd context if remap feature not enabled */ vma_start_write(vma); @@ -783,7 +788,9 @@ bool userfaultfd_remove(struct vm_area_struct *vma, return true; =20 userfaultfd_ctx_get(ctx); + down_write(&ctx->map_changing_lock); atomic_inc(&ctx->mmap_changing); + up_write(&ctx->map_changing_lock); mmap_read_unlock(mm); =20 msg_init(&ewq.msg); @@ -825,7 +832,9 @@ int userfaultfd_unmap_prep(struct vm_area_struct *vma, = unsigned long start, return -ENOMEM; =20 userfaultfd_ctx_get(ctx); + down_write(&ctx->map_changing_lock); atomic_inc(&ctx->mmap_changing); + up_write(&ctx->map_changing_lock); unmap_ctx->ctx =3D ctx; unmap_ctx->start =3D start; unmap_ctx->end =3D end; @@ -1709,9 +1718,8 @@ static int userfaultfd_copy(struct userfaultfd_ctx *c= tx, if (uffdio_copy.mode & UFFDIO_COPY_MODE_WP) flags |=3D MFILL_ATOMIC_WP; if (mmget_not_zero(ctx->mm)) { - ret =3D mfill_atomic_copy(ctx->mm, uffdio_copy.dst, uffdio_copy.src, - uffdio_copy.len, &ctx->mmap_changing, - flags); + ret =3D mfill_atomic_copy(ctx, uffdio_copy.dst, uffdio_copy.src, + uffdio_copy.len, flags); mmput(ctx->mm); } else { return -ESRCH; @@ -1761,9 +1769,8 @@ static int userfaultfd_zeropage(struct userfaultfd_ct= x *ctx, goto out; =20 if (mmget_not_zero(ctx->mm)) { - ret =3D mfill_atomic_zeropage(ctx->mm, uffdio_zeropage.range.start, - uffdio_zeropage.range.len, - &ctx->mmap_changing); + ret =3D mfill_atomic_zeropage(ctx, uffdio_zeropage.range.start, + uffdio_zeropage.range.len); mmput(ctx->mm); } else { return -ESRCH; @@ -1818,9 +1825,8 @@ static int userfaultfd_writeprotect(struct userfaultf= d_ctx *ctx, return -EINVAL; =20 if (mmget_not_zero(ctx->mm)) { - ret =3D mwriteprotect_range(ctx->mm, uffdio_wp.range.start, - uffdio_wp.range.len, mode_wp, - &ctx->mmap_changing); + ret =3D mwriteprotect_range(ctx, uffdio_wp.range.start, + uffdio_wp.range.len, mode_wp); mmput(ctx->mm); } else { return -ESRCH; @@ -1870,9 +1876,8 @@ static int userfaultfd_continue(struct userfaultfd_ct= x *ctx, unsigned long arg) flags |=3D MFILL_ATOMIC_WP; =20 if (mmget_not_zero(ctx->mm)) { - ret =3D mfill_atomic_continue(ctx->mm, uffdio_continue.range.start, - uffdio_continue.range.len, - &ctx->mmap_changing, flags); + ret =3D mfill_atomic_continue(ctx, uffdio_continue.range.start, + uffdio_continue.range.len, flags); mmput(ctx->mm); } else { return -ESRCH; @@ -1925,9 +1930,8 @@ static inline int userfaultfd_poison(struct userfault= fd_ctx *ctx, unsigned long goto out; =20 if (mmget_not_zero(ctx->mm)) { - ret =3D mfill_atomic_poison(ctx->mm, uffdio_poison.range.start, - uffdio_poison.range.len, - &ctx->mmap_changing, 0); + ret =3D mfill_atomic_poison(ctx, uffdio_poison.range.start, + uffdio_poison.range.len, 0); mmput(ctx->mm); } else { return -ESRCH; @@ -2003,13 +2007,14 @@ static int userfaultfd_move(struct userfaultfd_ctx = *ctx, if (mmget_not_zero(mm)) { mmap_read_lock(mm); =20 - /* Re-check after taking mmap_lock */ + /* Re-check after taking map_changing_lock */ + down_read(&ctx->map_changing_lock); if (likely(!atomic_read(&ctx->mmap_changing))) ret =3D move_pages(ctx, mm, uffdio_move.dst, uffdio_move.src, uffdio_move.len, uffdio_move.mode); else ret =3D -EAGAIN; - + up_read(&ctx->map_changing_lock); mmap_read_unlock(mm); mmput(mm); } else { @@ -2216,6 +2221,7 @@ static int new_userfaultfd(int flags) ctx->flags =3D flags; ctx->features =3D 0; ctx->released =3D false; + init_rwsem(&ctx->map_changing_lock); atomic_set(&ctx->mmap_changing, 0); ctx->mm =3D current->mm; /* prevent the mm struct to be freed */ diff --git a/include/linux/userfaultfd_k.h b/include/linux/userfaultfd_k.h index 691d928ee864..3210c3552976 100644 --- a/include/linux/userfaultfd_k.h +++ b/include/linux/userfaultfd_k.h @@ -69,6 +69,13 @@ struct userfaultfd_ctx { unsigned int features; /* released */ bool released; + /* + * Prevents userfaultfd operations (fill/move/wp) from happening while + * some non-cooperative event(s) is taking place. Increments are done + * in write-mode. Whereas, userfaultfd operations, which includes + * reading mmap_changing, is done under read-mode. + */ + struct rw_semaphore map_changing_lock; /* memory mappings are changing because of non-cooperative event */ atomic_t mmap_changing; /* mm with one ore more vmas attached to this userfaultfd_ctx */ @@ -113,22 +120,18 @@ extern int mfill_atomic_install_pte(pmd_t *dst_pmd, unsigned long dst_addr, struct page *page, bool newly_allocated, uffd_flags_t flags); =20 -extern ssize_t mfill_atomic_copy(struct mm_struct *dst_mm, unsigned long d= st_start, +extern ssize_t mfill_atomic_copy(struct userfaultfd_ctx *ctx, unsigned lon= g dst_start, unsigned long src_start, unsigned long len, - atomic_t *mmap_changing, uffd_flags_t flags); -extern ssize_t mfill_atomic_zeropage(struct mm_struct *dst_mm, + uffd_flags_t flags); +extern ssize_t mfill_atomic_zeropage(struct userfaultfd_ctx *ctx, unsigned long dst_start, - unsigned long len, - atomic_t *mmap_changing); -extern ssize_t mfill_atomic_continue(struct mm_struct *dst_mm, unsigned lo= ng dst_start, - unsigned long len, atomic_t *mmap_changing, - uffd_flags_t flags); -extern ssize_t mfill_atomic_poison(struct mm_struct *dst_mm, unsigned long= start, - unsigned long len, atomic_t *mmap_changing, - uffd_flags_t flags); -extern int mwriteprotect_range(struct mm_struct *dst_mm, - unsigned long start, unsigned long len, - bool enable_wp, atomic_t *mmap_changing); + unsigned long len); +extern ssize_t mfill_atomic_continue(struct userfaultfd_ctx *ctx, unsigned= long dst_start, + unsigned long len, uffd_flags_t flags); +extern ssize_t mfill_atomic_poison(struct userfaultfd_ctx *ctx, unsigned l= ong start, + unsigned long len, uffd_flags_t flags); +extern int mwriteprotect_range(struct userfaultfd_ctx *ctx, unsigned long = start, + unsigned long len, bool enable_wp); extern long uffd_wp_range(struct vm_area_struct *vma, unsigned long start, unsigned long len, bool enable_wp); =20 diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c index 9cc93cc1330b..74aad0831e40 100644 --- a/mm/userfaultfd.c +++ b/mm/userfaultfd.c @@ -353,11 +353,11 @@ static pmd_t *mm_alloc_pmd(struct mm_struct *mm, unsi= gned long address) * called with mmap_lock held, it will release mmap_lock before returning. */ static __always_inline ssize_t mfill_atomic_hugetlb( + struct userfaultfd_ctx *ctx, struct vm_area_struct *dst_vma, unsigned long dst_start, unsigned long src_start, unsigned long len, - atomic_t *mmap_changing, uffd_flags_t flags) { struct mm_struct *dst_mm =3D dst_vma->vm_mm; @@ -379,6 +379,7 @@ static __always_inline ssize_t mfill_atomic_hugetlb( * feature is not supported. */ if (uffd_flags_mode_is(flags, MFILL_ATOMIC_ZEROPAGE)) { + up_read(&ctx->map_changing_lock); mmap_read_unlock(dst_mm); return -EINVAL; } @@ -463,6 +464,7 @@ static __always_inline ssize_t mfill_atomic_hugetlb( cond_resched(); =20 if (unlikely(err =3D=3D -ENOENT)) { + up_read(&ctx->map_changing_lock); mmap_read_unlock(dst_mm); BUG_ON(!folio); =20 @@ -473,12 +475,13 @@ static __always_inline ssize_t mfill_atomic_hugetlb( goto out; } mmap_read_lock(dst_mm); + down_read(&ctx->map_changing_lock); /* * If memory mappings are changing because of non-cooperative * operation (e.g. mremap) running in parallel, bail out and * request the user to retry later */ - if (mmap_changing && atomic_read(mmap_changing)) { + if (atomic_read(&ctx->mmap_changing)) { err =3D -EAGAIN; break; } @@ -501,6 +504,7 @@ static __always_inline ssize_t mfill_atomic_hugetlb( } =20 out_unlock: + up_read(&ctx->map_changing_lock); mmap_read_unlock(dst_mm); out: if (folio) @@ -512,11 +516,11 @@ static __always_inline ssize_t mfill_atomic_hugetlb( } #else /* !CONFIG_HUGETLB_PAGE */ /* fail at build time if gcc attempts to use this */ -extern ssize_t mfill_atomic_hugetlb(struct vm_area_struct *dst_vma, +extern ssize_t mfill_atomic_hugetlb(struct userfaultfd_ctx *ctx, + struct vm_area_struct *dst_vma, unsigned long dst_start, unsigned long src_start, unsigned long len, - atomic_t *mmap_changing, uffd_flags_t flags); #endif /* CONFIG_HUGETLB_PAGE */ =20 @@ -564,13 +568,13 @@ static __always_inline ssize_t mfill_atomic_pte(pmd_t= *dst_pmd, return err; } =20 -static __always_inline ssize_t mfill_atomic(struct mm_struct *dst_mm, +static __always_inline ssize_t mfill_atomic(struct userfaultfd_ctx *ctx, unsigned long dst_start, unsigned long src_start, unsigned long len, - atomic_t *mmap_changing, uffd_flags_t flags) { + struct mm_struct *dst_mm =3D ctx->mm; struct vm_area_struct *dst_vma; ssize_t err; pmd_t *dst_pmd; @@ -600,8 +604,9 @@ static __always_inline ssize_t mfill_atomic(struct mm_s= truct *dst_mm, * operation (e.g. mremap) running in parallel, bail out and * request the user to retry later */ + down_read(&ctx->map_changing_lock); err =3D -EAGAIN; - if (mmap_changing && atomic_read(mmap_changing)) + if (atomic_read(&ctx->mmap_changing)) goto out_unlock; =20 /* @@ -633,8 +638,8 @@ static __always_inline ssize_t mfill_atomic(struct mm_s= truct *dst_mm, * If this is a HUGETLB vma, pass off to appropriate routine */ if (is_vm_hugetlb_page(dst_vma)) - return mfill_atomic_hugetlb(dst_vma, dst_start, src_start, - len, mmap_changing, flags); + return mfill_atomic_hugetlb(ctx, dst_vma, dst_start, + src_start, len, flags); =20 if (!vma_is_anonymous(dst_vma) && !vma_is_shmem(dst_vma)) goto out_unlock; @@ -693,6 +698,7 @@ static __always_inline ssize_t mfill_atomic(struct mm_s= truct *dst_mm, if (unlikely(err =3D=3D -ENOENT)) { void *kaddr; =20 + up_read(&ctx->map_changing_lock); mmap_read_unlock(dst_mm); BUG_ON(!folio); =20 @@ -723,6 +729,7 @@ static __always_inline ssize_t mfill_atomic(struct mm_s= truct *dst_mm, } =20 out_unlock: + up_read(&ctx->map_changing_lock); mmap_read_unlock(dst_mm); out: if (folio) @@ -733,34 +740,33 @@ static __always_inline ssize_t mfill_atomic(struct mm= _struct *dst_mm, return copied ? copied : err; } =20 -ssize_t mfill_atomic_copy(struct mm_struct *dst_mm, unsigned long dst_star= t, +ssize_t mfill_atomic_copy(struct userfaultfd_ctx *ctx, unsigned long dst_s= tart, unsigned long src_start, unsigned long len, - atomic_t *mmap_changing, uffd_flags_t flags) + uffd_flags_t flags) { - return mfill_atomic(dst_mm, dst_start, src_start, len, mmap_changing, + return mfill_atomic(ctx, dst_start, src_start, len, uffd_flags_set_mode(flags, MFILL_ATOMIC_COPY)); } =20 -ssize_t mfill_atomic_zeropage(struct mm_struct *dst_mm, unsigned long star= t, - unsigned long len, atomic_t *mmap_changing) +ssize_t mfill_atomic_zeropage(struct userfaultfd_ctx *ctx, + unsigned long start, + unsigned long len) { - return mfill_atomic(dst_mm, start, 0, len, mmap_changing, + return mfill_atomic(ctx, start, 0, len, uffd_flags_set_mode(0, MFILL_ATOMIC_ZEROPAGE)); } =20 -ssize_t mfill_atomic_continue(struct mm_struct *dst_mm, unsigned long star= t, - unsigned long len, atomic_t *mmap_changing, - uffd_flags_t flags) +ssize_t mfill_atomic_continue(struct userfaultfd_ctx *ctx, unsigned long s= tart, + unsigned long len, uffd_flags_t flags) { - return mfill_atomic(dst_mm, start, 0, len, mmap_changing, + return mfill_atomic(ctx, start, 0, len, uffd_flags_set_mode(flags, MFILL_ATOMIC_CONTINUE)); } =20 -ssize_t mfill_atomic_poison(struct mm_struct *dst_mm, unsigned long start, - unsigned long len, atomic_t *mmap_changing, - uffd_flags_t flags) +ssize_t mfill_atomic_poison(struct userfaultfd_ctx *ctx, unsigned long sta= rt, + unsigned long len, uffd_flags_t flags) { - return mfill_atomic(dst_mm, start, 0, len, mmap_changing, + return mfill_atomic(ctx, start, 0, len, uffd_flags_set_mode(flags, MFILL_ATOMIC_POISON)); } =20 @@ -793,10 +799,10 @@ long uffd_wp_range(struct vm_area_struct *dst_vma, return ret; } =20 -int mwriteprotect_range(struct mm_struct *dst_mm, unsigned long start, - unsigned long len, bool enable_wp, - atomic_t *mmap_changing) +int mwriteprotect_range(struct userfaultfd_ctx *ctx, unsigned long start, + unsigned long len, bool enable_wp) { + struct mm_struct *dst_mm =3D ctx->mm; unsigned long end =3D start + len; unsigned long _start, _end; struct vm_area_struct *dst_vma; @@ -820,8 +826,9 @@ int mwriteprotect_range(struct mm_struct *dst_mm, unsig= ned long start, * operation (e.g. mremap) running in parallel, bail out and * request the user to retry later */ + down_read(&ctx->map_changing_lock); err =3D -EAGAIN; - if (mmap_changing && atomic_read(mmap_changing)) + if (atomic_read(&ctx->mmap_changing)) goto out_unlock; =20 err =3D -ENOENT; @@ -850,6 +857,7 @@ int mwriteprotect_range(struct mm_struct *dst_mm, unsig= ned long start, err =3D 0; } out_unlock: + up_read(&ctx->map_changing_lock); mmap_read_unlock(dst_mm); return err; } --=20 2.43.0.687.g38aa6559b0-goog From nobody Mon Sep 16 20:23:42 2024 Received: from mail-yb1-f201.google.com (mail-yb1-f201.google.com [209.85.219.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 579E11482EA for ; Thu, 15 Feb 2024 18:28:15 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.219.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708021696; cv=none; b=jx1JV/KkfYVvOOdGA2qOkH+xeWTU+9TjddT5IWBeo6ZKc0lSs/nITcLPzCtFPndOEGLGs4zTeN787icsnRPQ8TbOig9HGglsAUcMuV7DRZRRoqGSyGHxyCj//eUtvCONDqAjO7qRQI2yRonNi0gEO0UwbgCSIHgiQW2vj/ck+cU= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708021696; c=relaxed/simple; bh=LpW+SzLj8BfVDIjFaKNHL0Ok3LPjc7UMqw1W2Wqi+nY=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=K6H2n+QrJmcMjrlAe7YwOKNOeiyEbD+z++nfeY99JpSQjmbyh3LEqOULugB/Jwy2QiM2OTxJmjZxdLVU/8n0vrKQQpmoQBlqIYNpvnylihYcL/HK8rkOLaRoU9wHJ3W+AYt6mkFeht+fN1QbBMP7psw9RfKqKdsN4ZPwdNHoowY= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--lokeshgidra.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=0rTxfC+e; arc=none smtp.client-ip=209.85.219.201 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--lokeshgidra.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="0rTxfC+e" Received: by mail-yb1-f201.google.com with SMTP id 3f1490d57ef6-dc6b267bf11so1474663276.2 for ; Thu, 15 Feb 2024 10:28:15 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1708021694; x=1708626494; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=2HDhVk/yBydR+FOGweImS2i3jLRp26hrWRjwdpWJGjA=; b=0rTxfC+eTBDYH3Z1M1HqIJWn7Goozw3FI73wRLEb0mMZCv227NJ6Ri02Y0Z3mA3/vY a/Q1gOxnf+xbG1REHzcTfer0LijnkT71tgOZVGfWDSGWqisQaHgJHjtgV/a0kRpLVrKI EumlOVtRD+jLj1IfQLimb/xRrYEWgEcctfFTFAb+8YyTmkdX4rlMENhpUb5xp35kvplu bnJcC1mYIyj48eUGY327JRxynEVLyeGjggw2YkMN1prqxqmkp5QBoS1rUtZC8axeVfR7 dZlVHtHctDe3+lOBqhnAffys4JnLG/4t2r4fC5bNDCYGlp8T3z8hawDo0J6XUyTzbl6h D2iA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1708021694; x=1708626494; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=2HDhVk/yBydR+FOGweImS2i3jLRp26hrWRjwdpWJGjA=; b=r4ySstuf65LmRRxf4jEAqYOrq4U/gU+Mp/oVgJtDBgafNL5WqLyPioByQGj2ZVF5nj jy7EEwAhNIX9oSriKCn2bPtR6IOfU9eAikaTk2kxJRYh5V9qY/QfZIO8kiSkne7PrIXc fywX6Z/ASCui7GZie8HLnMBAElrvveYHGgVJftrWnCPrRc+bTnX/trYsicudFA2cGt6h yLBhjPPQSdJm18NJA8SYQTy/mcbSI6PweFxjvNTmA9+hLyzAe+5hnIzFhnVTFB2AQj8l htNn5F16NhjBJeZnIrN0gkBwm17IlcNrd+2U5Hp2feB/wI7L2Le7yrbbLOONzEq02qI+ qbTQ== X-Forwarded-Encrypted: i=1; AJvYcCWcQSXWofuXYX7TncJ6o5CkhdWc83svdgjFUunAc19qErQ+gAMFoB3oaS11VCfnui1kq64diMb8AlcCPF/tXeKSlIKHjKnYisEmTm86 X-Gm-Message-State: AOJu0Yxp8WN0ZGocthjm/+zgUNouTb4kOaPcnOmu0dPermOAQut/NreJ A3VnQCUfDzrOYnmnVhaZ8ZuwBDHjvlvnWEoZX+ZcwYcPDt2s5SKItlbQI2+t8BIouz4CHieO5WG 2XM6sGpyyPIvFkHtgZQkCIg== X-Google-Smtp-Source: AGHT+IHQ/q6hEwod6dqa91JCy+4OwG7tKpKMnghYXGTo32mJNLEG+qzCG9zHFQLNQzOb5szaIYoSCz2kHnP0FoZoZg== X-Received: from lg.mtv.corp.google.com ([2620:15c:211:202:6186:87a3:6b94:9b81]) (user=lokeshgidra job=sendgmr) by 2002:a05:6902:100a:b0:dc6:c94e:fb85 with SMTP id w10-20020a056902100a00b00dc6c94efb85mr101286ybt.2.1708021694438; Thu, 15 Feb 2024 10:28:14 -0800 (PST) Date: Thu, 15 Feb 2024 10:27:55 -0800 In-Reply-To: <20240215182756.3448972-1-lokeshgidra@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20240215182756.3448972-1-lokeshgidra@google.com> X-Mailer: git-send-email 2.43.0.687.g38aa6559b0-goog Message-ID: <20240215182756.3448972-4-lokeshgidra@google.com> Subject: [PATCH v7 3/4] mm: add vma_assert_locked() for !CONFIG_PER_VMA_LOCK From: Lokesh Gidra To: akpm@linux-foundation.org Cc: lokeshgidra@google.com, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, selinux@vger.kernel.org, surenb@google.com, kernel-team@android.com, aarcange@redhat.com, peterx@redhat.com, david@redhat.com, axelrasmussen@google.com, bgeffon@google.com, willy@infradead.org, jannh@google.com, kaleshsingh@google.com, ngeoffray@google.com, timmurray@google.com, rppt@kernel.org, Liam.Howlett@oracle.com, ryan.roberts@arm.com Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" vma_assert_locked() is needed to replace mmap_assert_locked() once we start using per-vma locks in userfaultfd operations. In !CONFIG_PER_VMA_LOCK case when mm is locked, it implies that the given VMA is locked. Signed-off-by: Lokesh Gidra --- include/linux/mm.h | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/include/linux/mm.h b/include/linux/mm.h index 3c85634b186c..5ece3ad34ef8 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -781,6 +781,11 @@ static inline struct vm_area_struct *lock_vma_under_rc= u(struct mm_struct *mm, return NULL; } =20 +static inline void vma_assert_locked(struct vm_area_struct *vma) +{ + mmap_assert_locked(vma->vm_mm); +} + static inline void release_fault_lock(struct vm_fault *vmf) { mmap_read_unlock(vmf->vma->vm_mm); --=20 2.43.0.687.g38aa6559b0-goog From nobody Mon Sep 16 20:23:42 2024 Received: from mail-yw1-f201.google.com (mail-yw1-f201.google.com [209.85.128.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 58331148314 for ; Thu, 15 Feb 2024 18:28:17 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708021700; cv=none; b=ZKLmnDcPQBALsp2upHzMy4azjUjHLTYae0aeLim3uV2qtioRNTRMNDnsqcIFcznD88Vr94Ve4ssZ0tUhQlyCO7ZNh5jbi1x5J6QWFuENabTCNwsnWk2EqCUaYBPwOgiFvTnprCiEziHZcWRMRWWmAFBA+GHY15in5kIIxcuSAf4= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708021700; c=relaxed/simple; bh=R7NMKiXmQ2Fp2CZTF8zqri2+kmmTnnUwVA5YhhZQtwI=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=Y00vz2Zo0BaWtHqJ7XPYwX5tFhE+xuFelaRkP7GUf4CFWt2bMGD6rOP6JdyUl1nP5twKfFjyo/CnsAaXFrG9ZYZY0k8Ej3VLvqkMqVMWLEmhj2xLDnxZCBYE8tX99NinUkBvbatGe51aWZwhTmCfk2QkZx4pVPfh2utxuU7Ho70= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--lokeshgidra.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=V4EajePM; arc=none smtp.client-ip=209.85.128.201 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--lokeshgidra.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="V4EajePM" Received: by mail-yw1-f201.google.com with SMTP id 00721157ae682-60781e8709eso13869587b3.1 for ; Thu, 15 Feb 2024 10:28:17 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1708021696; x=1708626496; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=sdfVARy65CgD4hIH18dnYipXQIzvI+jzwwy4qPKyCEs=; b=V4EajePMHAwz3ZCwo69oRKCG4+5+wvoI7lLqjbH5sD16xXt16ez0lLF14J4cqALhQ8 fKlbIxuTyEj/RkIFu91rwix4FPPB3V305UG08B2szxAIYFVRkmVNq3xJyFh+kt1/zUx2 oxY9pbmUFnKuGvM64eqWhQw6/+rPNKVQACOLpR1lUXmdPcMV/o1BrccqSrXWkh+YwZrD 2lfvwHaEsWXAKgB6j6ueVoAnq8fyjmr1gvKI/pmGIDUUKcVBV7GZWkpTg7ZRXLN5BQKj tikxfSJ7NBs/oFvIneZatW4iNexIucaTI2IYMR2lLagJ3WuBSdlQk9GmeOR+5IzZSFcA tOAg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1708021696; x=1708626496; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=sdfVARy65CgD4hIH18dnYipXQIzvI+jzwwy4qPKyCEs=; b=kQ0717lZ8+hLiUPzrKZ8Boyv051OmGL5g58XMjsOkPfRl9JOrCHAClK5c4Qio6OKrE MwyRycUlyM93v06yx/OOhbBOCUC8lRoJcfhApkadP0HEiOsgC4zuMjvB2iNv7BeqTOfb ac2XoJFdyiQDgmUcR0/8Sit57UT9XnJ2dWc/+mtRPqjf+FKp18Ju7eB6vQAS2NN+vrI4 evF561RApwugXv9wdDCPBVz6N5NbnMBrXQkFu3TISdeOSR4T9hg/92WI4qnpHKLfhkZR /j9U5W/Xq+37Z2l2UsOv1ixHoHCQ1G+7CZZANto79tIIabknxng4DcpwLAynCnxz5STm bM9A== X-Forwarded-Encrypted: i=1; AJvYcCX7L0sABPMNV9KeOzXxxxjQUgYSfFtI6hUwwI1Cy3PmtWa3LEWvTyMY/Cgx0+2trVhpoHcx/uWJBlOQ58SPyJXcARw0hYyYrapNbb3O X-Gm-Message-State: AOJu0Yw/z1R9wA5SbDkaF4bKfOxMS+LNJkDpB1ALNE/RsI+ij6sDveJu y0RsUCmEKNZ1SMmUy1thfqwAMXShVlBDiX0cwW0OF3UTzf9A7+cCBBn9oDz7TLmpcGly+jT2CEx vjhr0NOZksi1y36KtRNM7oA== X-Google-Smtp-Source: AGHT+IHGae+uPzrc4Hv5tlNVkUxfz8K6+IwOsbpum+6krBpkrYXvIIY2FdVy1Ib5pZBj1K2oQGCjrbGbqVY/rhISHw== X-Received: from lg.mtv.corp.google.com ([2620:15c:211:202:6186:87a3:6b94:9b81]) (user=lokeshgidra job=sendgmr) by 2002:a81:4402:0:b0:607:7927:dea1 with SMTP id r2-20020a814402000000b006077927dea1mr1073112ywa.1.1708021696307; Thu, 15 Feb 2024 10:28:16 -0800 (PST) Date: Thu, 15 Feb 2024 10:27:56 -0800 In-Reply-To: <20240215182756.3448972-1-lokeshgidra@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20240215182756.3448972-1-lokeshgidra@google.com> X-Mailer: git-send-email 2.43.0.687.g38aa6559b0-goog Message-ID: <20240215182756.3448972-5-lokeshgidra@google.com> Subject: [PATCH v7 4/4] userfaultfd: use per-vma locks in userfaultfd operations From: Lokesh Gidra To: akpm@linux-foundation.org Cc: lokeshgidra@google.com, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, selinux@vger.kernel.org, surenb@google.com, kernel-team@android.com, aarcange@redhat.com, peterx@redhat.com, david@redhat.com, axelrasmussen@google.com, bgeffon@google.com, willy@infradead.org, jannh@google.com, kaleshsingh@google.com, ngeoffray@google.com, timmurray@google.com, rppt@kernel.org, Liam.Howlett@oracle.com, ryan.roberts@arm.com Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" All userfaultfd operations, except write-protect, opportunistically use per-vma locks to lock vmas. On failure, attempt again inside mmap_lock critical section. Write-protect operation requires mmap_lock as it iterates over multiple vmas. Signed-off-by: Lokesh Gidra Reviewed-by: Liam R. Howlett --- fs/userfaultfd.c | 13 +- include/linux/userfaultfd_k.h | 5 +- mm/huge_memory.c | 5 +- mm/userfaultfd.c | 380 ++++++++++++++++++++++++++-------- 4 files changed, 299 insertions(+), 104 deletions(-) diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c index c00a021bcce4..60dcfafdc11a 100644 --- a/fs/userfaultfd.c +++ b/fs/userfaultfd.c @@ -2005,17 +2005,8 @@ static int userfaultfd_move(struct userfaultfd_ctx *= ctx, return -EINVAL; =20 if (mmget_not_zero(mm)) { - mmap_read_lock(mm); - - /* Re-check after taking map_changing_lock */ - down_read(&ctx->map_changing_lock); - if (likely(!atomic_read(&ctx->mmap_changing))) - ret =3D move_pages(ctx, mm, uffdio_move.dst, uffdio_move.src, - uffdio_move.len, uffdio_move.mode); - else - ret =3D -EAGAIN; - up_read(&ctx->map_changing_lock); - mmap_read_unlock(mm); + ret =3D move_pages(ctx, uffdio_move.dst, uffdio_move.src, + uffdio_move.len, uffdio_move.mode); mmput(mm); } else { return -ESRCH; diff --git a/include/linux/userfaultfd_k.h b/include/linux/userfaultfd_k.h index 3210c3552976..05d59f74fc88 100644 --- a/include/linux/userfaultfd_k.h +++ b/include/linux/userfaultfd_k.h @@ -138,9 +138,8 @@ extern long uffd_wp_range(struct vm_area_struct *vma, /* move_pages */ void double_pt_lock(spinlock_t *ptl1, spinlock_t *ptl2); void double_pt_unlock(spinlock_t *ptl1, spinlock_t *ptl2); -ssize_t move_pages(struct userfaultfd_ctx *ctx, struct mm_struct *mm, - unsigned long dst_start, unsigned long src_start, - unsigned long len, __u64 flags); +ssize_t move_pages(struct userfaultfd_ctx *ctx, unsigned long dst_start, + unsigned long src_start, unsigned long len, __u64 flags); int move_pages_huge_pmd(struct mm_struct *mm, pmd_t *dst_pmd, pmd_t *src_p= md, pmd_t dst_pmdval, struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma, diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 016e20bd813e..c337ebb4f7ab 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2158,7 +2158,7 @@ int change_huge_pmd(struct mmu_gather *tlb, struct vm= _area_struct *vma, =20 #ifdef CONFIG_USERFAULTFD /* - * The PT lock for src_pmd and the mmap_lock for reading are held by + * The PT lock for src_pmd and dst_vma/src_vma (for reading) are locked by * the caller, but it must return after releasing the page_table_lock. * Just move the page from src_pmd to dst_pmd if possible. * Return zero if succeeded in moving the page, -EAGAIN if it needs to be @@ -2181,7 +2181,8 @@ int move_pages_huge_pmd(struct mm_struct *mm, pmd_t *= dst_pmd, pmd_t *src_pmd, pm src_ptl =3D pmd_lockptr(mm, src_pmd); =20 lockdep_assert_held(src_ptl); - mmap_assert_locked(mm); + vma_assert_locked(src_vma); + vma_assert_locked(dst_vma); =20 /* Sanity checks before the operation */ if (WARN_ON_ONCE(!pmd_none(dst_pmdval)) || WARN_ON_ONCE(src_addr & ~HPAGE= _PMD_MASK) || diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c index 74aad0831e40..4744d6a96f96 100644 --- a/mm/userfaultfd.c +++ b/mm/userfaultfd.c @@ -20,19 +20,11 @@ #include "internal.h" =20 static __always_inline -struct vm_area_struct *find_dst_vma(struct mm_struct *dst_mm, - unsigned long dst_start, - unsigned long len) +bool validate_dst_vma(struct vm_area_struct *dst_vma, unsigned long dst_en= d) { - /* - * Make sure that the dst range is both valid and fully within a - * single existing vma. - */ - struct vm_area_struct *dst_vma; - - dst_vma =3D find_vma(dst_mm, dst_start); - if (!range_in_vma(dst_vma, dst_start, dst_start + len)) - return NULL; + /* Make sure that the dst range is fully within dst_vma. */ + if (dst_end > dst_vma->vm_end) + return false; =20 /* * Check the vma is registered in uffd, this is required to @@ -40,11 +32,122 @@ struct vm_area_struct *find_dst_vma(struct mm_struct *= dst_mm, * time. */ if (!dst_vma->vm_userfaultfd_ctx.ctx) - return NULL; + return false; + + return true; +} + +static __always_inline +struct vm_area_struct *find_vma_and_prepare_anon(struct mm_struct *mm, + unsigned long addr) +{ + struct vm_area_struct *vma; + + mmap_assert_locked(mm); + vma =3D vma_lookup(mm, addr); + if (!vma) + vma =3D ERR_PTR(-ENOENT); + else if (!(vma->vm_flags & VM_SHARED) && + unlikely(anon_vma_prepare(vma))) + vma =3D ERR_PTR(-ENOMEM); + + return vma; +} + +#ifdef CONFIG_PER_VMA_LOCK +/* + * lock_vma() - Lookup and lock vma corresponding to @address. + * @mm: mm to search vma in. + * @address: address that the vma should contain. + * + * Should be called without holding mmap_lock. vma should be unlocked afte= r use + * with unlock_vma(). + * + * Return: A locked vma containing @address, -ENOENT if no vma is found, or + * -ENOMEM if anon_vma couldn't be allocated. + */ +static struct vm_area_struct *lock_vma(struct mm_struct *mm, + unsigned long address) +{ + struct vm_area_struct *vma; + + vma =3D lock_vma_under_rcu(mm, address); + if (vma) { + /* + * lock_vma_under_rcu() only checks anon_vma for private + * anonymous mappings. But we need to ensure it is assigned in + * private file-backed vmas as well. + */ + if (!(vma->vm_flags & VM_SHARED) && unlikely(!vma->anon_vma)) + vma_end_read(vma); + else + return vma; + } + + mmap_read_lock(mm); + vma =3D find_vma_and_prepare_anon(mm, address); + if (!IS_ERR(vma)) { + /* + * We cannot use vma_start_read() as it may fail due to + * false locked (see comment in vma_start_read()). We + * can avoid that by directly locking vm_lock under + * mmap_lock, which guarantees that nobody can lock the + * vma for write (vma_start_write()) under us. + */ + down_read(&vma->vm_lock->lock); + } + + mmap_read_unlock(mm); + return vma; +} + +static struct vm_area_struct *uffd_mfill_lock(struct mm_struct *dst_mm, + unsigned long dst_start, + unsigned long len) +{ + struct vm_area_struct *dst_vma; =20 + dst_vma =3D lock_vma(dst_mm, dst_start); + if (IS_ERR(dst_vma) || validate_dst_vma(dst_vma, dst_start + len)) + return dst_vma; + + vma_end_read(dst_vma); + return ERR_PTR(-ENOENT); +} + +static void uffd_mfill_unlock(struct vm_area_struct *vma) +{ + vma_end_read(vma); +} + +#else + +static struct vm_area_struct *uffd_mfill_lock(struct mm_struct *dst_mm, + unsigned long dst_start, + unsigned long len) +{ + struct vm_area_struct *dst_vma; + + mmap_read_lock(dst_mm); + dst_vma =3D find_vma_and_prepare_anon(dst_mm, dst_start); + if (IS_ERR(dst_vma)) + goto out_unlock; + + if (validate_dst_vma(dst_vma, dst_start + len)) + return dst_vma; + + dst_vma =3D ERR_PTR(-ENOENT); +out_unlock: + mmap_read_unlock(dst_mm); return dst_vma; } =20 +static void uffd_mfill_unlock(struct vm_area_struct *vma) +{ + mmap_read_unlock(vma->vm_mm); +} +#endif + /* Check if dst_addr is outside of file's size. Must be called with ptl he= ld. */ static bool mfill_file_over_size(struct vm_area_struct *dst_vma, unsigned long dst_addr) @@ -350,7 +453,8 @@ static pmd_t *mm_alloc_pmd(struct mm_struct *mm, unsign= ed long address) #ifdef CONFIG_HUGETLB_PAGE /* * mfill_atomic processing for HUGETLB vmas. Note that this routine is - * called with mmap_lock held, it will release mmap_lock before returning. + * called with either vma-lock or mmap_lock held, it will release the lock + * before returning. */ static __always_inline ssize_t mfill_atomic_hugetlb( struct userfaultfd_ctx *ctx, @@ -361,7 +465,6 @@ static __always_inline ssize_t mfill_atomic_hugetlb( uffd_flags_t flags) { struct mm_struct *dst_mm =3D dst_vma->vm_mm; - int vm_shared =3D dst_vma->vm_flags & VM_SHARED; ssize_t err; pte_t *dst_pte; unsigned long src_addr, dst_addr; @@ -380,7 +483,7 @@ static __always_inline ssize_t mfill_atomic_hugetlb( */ if (uffd_flags_mode_is(flags, MFILL_ATOMIC_ZEROPAGE)) { up_read(&ctx->map_changing_lock); - mmap_read_unlock(dst_mm); + uffd_mfill_unlock(dst_vma); return -EINVAL; } =20 @@ -403,24 +506,28 @@ static __always_inline ssize_t mfill_atomic_hugetlb( * retry, dst_vma will be set to NULL and we must lookup again. */ if (!dst_vma) { + dst_vma =3D uffd_mfill_lock(dst_mm, dst_start, len); + if (IS_ERR(dst_vma)) { + err =3D PTR_ERR(dst_vma); + goto out; + } + err =3D -ENOENT; - dst_vma =3D find_dst_vma(dst_mm, dst_start, len); - if (!dst_vma || !is_vm_hugetlb_page(dst_vma)) - goto out_unlock; + if (!is_vm_hugetlb_page(dst_vma)) + goto out_unlock_vma; =20 err =3D -EINVAL; if (vma_hpagesize !=3D vma_kernel_pagesize(dst_vma)) - goto out_unlock; - - vm_shared =3D dst_vma->vm_flags & VM_SHARED; - } + goto out_unlock_vma; =20 - /* - * If not shared, ensure the dst_vma has a anon_vma. - */ - err =3D -ENOMEM; - if (!vm_shared) { - if (unlikely(anon_vma_prepare(dst_vma))) + /* + * If memory mappings are changing because of non-cooperative + * operation (e.g. mremap) running in parallel, bail out and + * request the user to retry later + */ + down_read(&ctx->map_changing_lock); + err =3D -EAGAIN; + if (atomic_read(&ctx->mmap_changing)) goto out_unlock; } =20 @@ -465,7 +572,7 @@ static __always_inline ssize_t mfill_atomic_hugetlb( =20 if (unlikely(err =3D=3D -ENOENT)) { up_read(&ctx->map_changing_lock); - mmap_read_unlock(dst_mm); + uffd_mfill_unlock(dst_vma); BUG_ON(!folio); =20 err =3D copy_folio_from_user(folio, @@ -474,17 +581,6 @@ static __always_inline ssize_t mfill_atomic_hugetlb( err =3D -EFAULT; goto out; } - mmap_read_lock(dst_mm); - down_read(&ctx->map_changing_lock); - /* - * If memory mappings are changing because of non-cooperative - * operation (e.g. mremap) running in parallel, bail out and - * request the user to retry later - */ - if (atomic_read(&ctx->mmap_changing)) { - err =3D -EAGAIN; - break; - } =20 dst_vma =3D NULL; goto retry; @@ -505,7 +601,8 @@ static __always_inline ssize_t mfill_atomic_hugetlb( =20 out_unlock: up_read(&ctx->map_changing_lock); - mmap_read_unlock(dst_mm); +out_unlock_vma: + uffd_mfill_unlock(dst_vma); out: if (folio) folio_put(folio); @@ -597,7 +694,15 @@ static __always_inline ssize_t mfill_atomic(struct use= rfaultfd_ctx *ctx, copied =3D 0; folio =3D NULL; retry: - mmap_read_lock(dst_mm); + /* + * Make sure the vma is not shared, that the dst range is + * both valid and fully within a single existing vma. + */ + dst_vma =3D uffd_mfill_lock(dst_mm, dst_start, len); + if (IS_ERR(dst_vma)) { + err =3D PTR_ERR(dst_vma); + goto out; + } =20 /* * If memory mappings are changing because of non-cooperative @@ -609,15 +714,6 @@ static __always_inline ssize_t mfill_atomic(struct use= rfaultfd_ctx *ctx, if (atomic_read(&ctx->mmap_changing)) goto out_unlock; =20 - /* - * Make sure the vma is not shared, that the dst range is - * both valid and fully within a single existing vma. - */ - err =3D -ENOENT; - dst_vma =3D find_dst_vma(dst_mm, dst_start, len); - if (!dst_vma) - goto out_unlock; - err =3D -EINVAL; /* * shmem_zero_setup is invoked in mmap for MAP_ANONYMOUS|MAP_SHARED but @@ -647,16 +743,6 @@ static __always_inline ssize_t mfill_atomic(struct use= rfaultfd_ctx *ctx, uffd_flags_mode_is(flags, MFILL_ATOMIC_CONTINUE)) goto out_unlock; =20 - /* - * Ensure the dst_vma has a anon_vma or this page - * would get a NULL anon_vma when moved in the - * dst_vma. - */ - err =3D -ENOMEM; - if (!(dst_vma->vm_flags & VM_SHARED) && - unlikely(anon_vma_prepare(dst_vma))) - goto out_unlock; - while (src_addr < src_start + len) { pmd_t dst_pmdval; =20 @@ -699,7 +785,7 @@ static __always_inline ssize_t mfill_atomic(struct user= faultfd_ctx *ctx, void *kaddr; =20 up_read(&ctx->map_changing_lock); - mmap_read_unlock(dst_mm); + uffd_mfill_unlock(dst_vma); BUG_ON(!folio); =20 kaddr =3D kmap_local_folio(folio, 0); @@ -730,7 +816,7 @@ static __always_inline ssize_t mfill_atomic(struct user= faultfd_ctx *ctx, =20 out_unlock: up_read(&ctx->map_changing_lock); - mmap_read_unlock(dst_mm); + uffd_mfill_unlock(dst_vma); out: if (folio) folio_put(folio); @@ -1267,27 +1353,136 @@ static int validate_move_areas(struct userfaultfd_= ctx *ctx, if (!vma_is_anonymous(src_vma) || !vma_is_anonymous(dst_vma)) return -EINVAL; =20 + return 0; +} + +static __always_inline +int find_vmas_mm_locked(struct mm_struct *mm, + unsigned long dst_start, + unsigned long src_start, + struct vm_area_struct **dst_vmap, + struct vm_area_struct **src_vmap) +{ + struct vm_area_struct *vma; + + mmap_assert_locked(mm); + vma =3D find_vma_and_prepare_anon(mm, dst_start); + if (IS_ERR(vma)) + return PTR_ERR(vma); + + *dst_vmap =3D vma; + /* Skip finding src_vma if src_start is in dst_vma */ + if (src_start >=3D vma->vm_start && src_start < vma->vm_end) + goto out_success; + + vma =3D vma_lookup(mm, src_start); + if (!vma) + return -ENOENT; +out_success: + *src_vmap =3D vma; + return 0; +} + +#ifdef CONFIG_PER_VMA_LOCK +static int uffd_move_lock(struct mm_struct *mm, + unsigned long dst_start, + unsigned long src_start, + struct vm_area_struct **dst_vmap, + struct vm_area_struct **src_vmap) +{ + struct vm_area_struct *vma; + int err; + + vma =3D lock_vma(mm, dst_start); + if (IS_ERR(vma)) + return PTR_ERR(vma); + + *dst_vmap =3D vma; /* - * Ensure the dst_vma has a anon_vma or this page - * would get a NULL anon_vma when moved in the - * dst_vma. + * Skip finding src_vma if src_start is in dst_vma. This also ensures + * that we don't lock the same vma twice. */ - if (unlikely(anon_vma_prepare(dst_vma))) - return -ENOMEM; + if (src_start >=3D vma->vm_start && src_start < vma->vm_end) { + *src_vmap =3D vma; + return 0; + } =20 - return 0; + /* + * Using lock_vma() to get src_vma can lead to following deadlock: + * + * Thread1 Thread2 + * ------- ------- + * vma_start_read(dst_vma) + * mmap_write_lock(mm) + * vma_start_write(src_vma) + * vma_start_read(src_vma) + * mmap_read_lock(mm) + * vma_start_write(dst_vma) + */ + *src_vmap =3D lock_vma_under_rcu(mm, src_start); + if (likely(*src_vmap)) + return 0; + + /* Undo any locking and retry in mmap_lock critical section */ + vma_end_read(*dst_vmap); + + mmap_read_lock(mm); + err =3D find_vmas_mm_locked(mm, dst_start, src_start, dst_vmap, src_vmap); + if (!err) { + /* + * See comment in lock_vma() as to why not using + * vma_start_read() here. + */ + down_read(&(*dst_vmap)->vm_lock->lock); + if (*dst_vmap !=3D *src_vmap) + down_read(&(*src_vmap)->vm_lock->lock); + } + mmap_read_unlock(mm); + return err; +} + +static void uffd_move_unlock(struct vm_area_struct *dst_vma, + struct vm_area_struct *src_vma) +{ + vma_end_read(src_vma); + if (src_vma !=3D dst_vma) + vma_end_read(dst_vma); } =20 +#else + +static int uffd_move_lock(struct mm_struct *mm, + unsigned long dst_start, + unsigned long src_start, + struct vm_area_struct **dst_vmap, + struct vm_area_struct **src_vmap) +{ + int err; + + mmap_read_lock(mm); + err =3D find_vmas_mm_locked(mm, dst_start, src_start, dst_vmap, src_vmap); + if (err) + mmap_read_unlock(mm); + return err; +} + +static void uffd_move_unlock(struct vm_area_struct *dst_vma, + struct vm_area_struct *src_vma) +{ + mmap_assert_locked(src_vma->vm_mm); + mmap_read_unlock(dst_vma->vm_mm); +} +#endif + /** * move_pages - move arbitrary anonymous pages of an existing vma * @ctx: pointer to the userfaultfd context - * @mm: the address space to move pages * @dst_start: start of the destination virtual memory range * @src_start: start of the source virtual memory range * @len: length of the virtual memory range * @mode: flags from uffdio_move.mode * - * Must be called with mmap_lock held for read. + * It will either use the mmap_lock in read mode or per-vma locks * * move_pages() remaps arbitrary anonymous pages atomically in zero * copy. It only works on non shared anonymous pages because those can @@ -1355,10 +1550,10 @@ static int validate_move_areas(struct userfaultfd_c= tx *ctx, * could be obtained. This is the only additional complexity added to * the rmap code to provide this anonymous page remapping functionality. */ -ssize_t move_pages(struct userfaultfd_ctx *ctx, struct mm_struct *mm, - unsigned long dst_start, unsigned long src_start, - unsigned long len, __u64 mode) +ssize_t move_pages(struct userfaultfd_ctx *ctx, unsigned long dst_start, + unsigned long src_start, unsigned long len, __u64 mode) { + struct mm_struct *mm =3D ctx->mm; struct vm_area_struct *src_vma, *dst_vma; unsigned long src_addr, dst_addr; pmd_t *src_pmd, *dst_pmd; @@ -1376,28 +1571,34 @@ ssize_t move_pages(struct userfaultfd_ctx *ctx, str= uct mm_struct *mm, WARN_ON_ONCE(dst_start + len <=3D dst_start)) goto out; =20 + err =3D uffd_move_lock(mm, dst_start, src_start, &dst_vma, &src_vma); + if (err) + goto out; + + /* Re-check after taking map_changing_lock */ + err =3D -EAGAIN; + down_read(&ctx->map_changing_lock); + if (likely(atomic_read(&ctx->mmap_changing))) + goto out_unlock; /* * Make sure the vma is not shared, that the src and dst remap * ranges are both valid and fully within a single existing * vma. */ - src_vma =3D find_vma(mm, src_start); - if (!src_vma || (src_vma->vm_flags & VM_SHARED)) - goto out; - if (src_start < src_vma->vm_start || - src_start + len > src_vma->vm_end) - goto out; + err =3D -EINVAL; + if (src_vma->vm_flags & VM_SHARED) + goto out_unlock; + if (src_start + len > src_vma->vm_end) + goto out_unlock; =20 - dst_vma =3D find_vma(mm, dst_start); - if (!dst_vma || (dst_vma->vm_flags & VM_SHARED)) - goto out; - if (dst_start < dst_vma->vm_start || - dst_start + len > dst_vma->vm_end) - goto out; + if (dst_vma->vm_flags & VM_SHARED) + goto out_unlock; + if (dst_start + len > dst_vma->vm_end) + goto out_unlock; =20 err =3D validate_move_areas(ctx, src_vma, dst_vma); if (err) - goto out; + goto out_unlock; =20 for (src_addr =3D src_start, dst_addr =3D dst_start; src_addr < src_start + len;) { @@ -1514,6 +1715,9 @@ ssize_t move_pages(struct userfaultfd_ctx *ctx, struc= t mm_struct *mm, moved +=3D step_size; } =20 +out_unlock: + up_read(&ctx->map_changing_lock); + uffd_move_unlock(dst_vma, src_vma); out: VM_WARN_ON(moved < 0); VM_WARN_ON(err > 0); --=20 2.43.0.687.g38aa6559b0-goog