From nobody Sun Feb 8 15:29:00 2026 Received: from mail-pj1-f73.google.com (mail-pj1-f73.google.com [209.85.216.73]) (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 6AE54188012 for ; Sat, 11 Jan 2025 04:26:23 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.216.73 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1736569584; cv=none; b=CBadKRUIQdIUxipum9CB+QjbLM2Yx8w5F/GIn5aD2LOnspJlroGXYGvJhwGV1CRPvKxNyNC2TxbJ6HhIcnY+N8V2ogZ8VfvBtQVXYw1cZpqTbB2GD2vOCh+GRVKZe/5Ujo6fiNydzYcYH1kT8HcgpTfnumpxyDTLQ0Xrnkt3+7c= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1736569584; c=relaxed/simple; bh=RBaZ74So51j4aqXC7AuC9vLEqhQDweY9kqrtQ5fJJDc=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=jUcA8ZN919HYWVHR6EwzXBnzaWgsWPjsapVLyXARTj9wuqZCKSrfLDc8qZk5EYAtAdIgut7h/oVJEi2peQx8s+tFu+toj0imFrG1sZ9rJ6n+kFtnWWzCvMm69ZsXzqaCukUlR3Pq58fEHyTnkLV+Q+E6nUncaI4q6JnT5t62E2w= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--surenb.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=wAypSoED; arc=none smtp.client-ip=209.85.216.73 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--surenb.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="wAypSoED" Received: by mail-pj1-f73.google.com with SMTP id 98e67ed59e1d1-2ef91d5c863so4898280a91.2 for ; Fri, 10 Jan 2025 20:26:23 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1736569583; x=1737174383; 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=7fOHsmOPwrKtQ1EzbWANyGDHIimQCM8l7vZM7q2M3lw=; b=wAypSoEDpEaoDCUnIRT8RsQ65BeO5tVZBgYysFtNh62/V6ObPFscpK26rsnX7XLiGh lG8AnDPzMe4GIUGY7YAIsa59L9fBzWXyhw0g3kjuI4+al8WLpd22u9XZrX8TSeAiZQFy gCubBlSUUcdg0DZMj0J5S18kz81ViUfpJeGRYmLg550MKIjglsG9zX9DyREXc/7+ejpW BdZTRx/zlLt3RuhM1yUcrFew+bM5SkgnrX9UzwJ+/OaLN9th53Khb5e5wwqNclfUKG2/ WHgB/HAACd/uyChATLRpy5NPtw4CucHA4LoUJ61OplGeCSVWFREBgM4nxnZzJqCnJ3V+ 8qVQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1736569583; x=1737174383; 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=7fOHsmOPwrKtQ1EzbWANyGDHIimQCM8l7vZM7q2M3lw=; b=vTihw1OPtOG9n91BmJvHTM8MObgev2xrUfH1LsB2paLuObYNPva5dgQGjKg68uMwRs /1ezLC+V/2aDNJ6InAOACMDWORfYBItTvRmUGTUBr3t7CKB92uV5ae7L4f4AWZ0s9ET6 zTQdwPa5GgkDCV5gWhl9S7OtbbWe0H+iHOg2t23aSpOk3R7Wt1TQBn5Hp5lpDWZ16E/y IaEioAalru/v4VmQn0qT63I65alqI/Y1VzVQ30Jz/X+Snv392JRkUD9fThAC710zKOlt q4dGJAguc889Bmp1bRu9URavATlA/s86b4HyUJ6VcItinzIhdkadPdESO7spCWw/rKjk YukQ== X-Forwarded-Encrypted: i=1; AJvYcCWb/XYeTDBxlMP6Qoya6GNCQ0W3q/MVZmqFSkzRhyE6FaETzYFSnDljpEc/yjbEdSfbl11s4NM6CxpJRMs=@vger.kernel.org X-Gm-Message-State: AOJu0YyKRKj273azfQSIRqmcdOR8iMi5uN2jBYikuJ9+7x/UIhJfq+wZ n4dL7NydLQ1uoPHAr1d2qaaBNnVbiTH2jnjOCl6cFSi9GXBcDNMZtzn/ITzQvPRe2bhXYGPz4xu q4w== X-Google-Smtp-Source: AGHT+IEri6oWvbwaR9NKB8OaH7pKRVw+NxMfmWZU4bRXuSK8tL89q2iubRxHeJuXJzsmqdnV3Y+AwYimngo= X-Received: from pjbsl14.prod.google.com ([2002:a17:90b:2e0e:b0:2ef:8f54:4254]) (user=surenb job=prod-delivery.src-stubby-dispatcher) by 2002:a17:90a:da88:b0:2ee:5111:a54b with SMTP id 98e67ed59e1d1-2f548f424c7mr16967174a91.31.1736569582930; Fri, 10 Jan 2025 20:26:22 -0800 (PST) Date: Fri, 10 Jan 2025 20:25:54 -0800 In-Reply-To: <20250111042604.3230628-1-surenb@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20250111042604.3230628-1-surenb@google.com> X-Mailer: git-send-email 2.47.1.613.gc27f4b7a9f-goog Message-ID: <20250111042604.3230628-8-surenb@google.com> Subject: [PATCH v9 07/17] mm: allow vma_start_read_locked/vma_start_read_locked_nested to fail From: Suren Baghdasaryan To: akpm@linux-foundation.org Cc: peterz@infradead.org, willy@infradead.org, liam.howlett@oracle.com, lorenzo.stoakes@oracle.com, david.laight.linux@gmail.com, mhocko@suse.com, vbabka@suse.cz, hannes@cmpxchg.org, mjguzik@gmail.com, oliver.sang@intel.com, mgorman@techsingularity.net, david@redhat.com, peterx@redhat.com, oleg@redhat.com, dave@stgolabs.net, paulmck@kernel.org, brauner@kernel.org, dhowells@redhat.com, hdanton@sina.com, hughd@google.com, lokeshgidra@google.com, minchan@google.com, jannh@google.com, shakeel.butt@linux.dev, souravpanda@google.com, pasha.tatashin@soleen.com, klarasmodin@gmail.com, richard.weiyang@gmail.com, corbet@lwn.net, linux-doc@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team@android.com, surenb@google.com Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" With upcoming replacement of vm_lock with vm_refcnt, we need to handle a possibility of vma_start_read_locked/vma_start_read_locked_nested failing due to refcount overflow. Prepare for such possibility by changing these APIs and adjusting their users. Signed-off-by: Suren Baghdasaryan Acked-by: Vlastimil Babka Cc: Lokesh Gidra --- include/linux/mm.h | 6 ++++-- mm/userfaultfd.c | 18 +++++++++++++----- 2 files changed, 17 insertions(+), 7 deletions(-) diff --git a/include/linux/mm.h b/include/linux/mm.h index 2f805f1a0176..cbb4e3dbbaed 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -747,10 +747,11 @@ static inline bool vma_start_read(struct vm_area_stru= ct *vma) * not be used in such cases because it might fail due to mm_lock_seq over= flow. * This functionality is used to obtain vma read lock and drop the mmap re= ad lock. */ -static inline void vma_start_read_locked_nested(struct vm_area_struct *vma= , int subclass) +static inline bool vma_start_read_locked_nested(struct vm_area_struct *vma= , int subclass) { mmap_assert_locked(vma->vm_mm); down_read_nested(&vma->vm_lock.lock, subclass); + return true; } =20 /* @@ -759,10 +760,11 @@ static inline void vma_start_read_locked_nested(struc= t vm_area_struct *vma, int * not be used in such cases because it might fail due to mm_lock_seq over= flow. * This functionality is used to obtain vma read lock and drop the mmap re= ad lock. */ -static inline void vma_start_read_locked(struct vm_area_struct *vma) +static inline bool vma_start_read_locked(struct vm_area_struct *vma) { mmap_assert_locked(vma->vm_mm); down_read(&vma->vm_lock.lock); + return true; } =20 static inline void vma_end_read(struct vm_area_struct *vma) diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c index 4527c385935b..411a663932c4 100644 --- a/mm/userfaultfd.c +++ b/mm/userfaultfd.c @@ -85,7 +85,8 @@ static struct vm_area_struct *uffd_lock_vma(struct mm_str= uct *mm, mmap_read_lock(mm); vma =3D find_vma_and_prepare_anon(mm, address); if (!IS_ERR(vma)) - vma_start_read_locked(vma); + if (!vma_start_read_locked(vma)) + vma =3D ERR_PTR(-EAGAIN); =20 mmap_read_unlock(mm); return vma; @@ -1483,10 +1484,17 @@ static int uffd_move_lock(struct mm_struct *mm, mmap_read_lock(mm); err =3D find_vmas_mm_locked(mm, dst_start, src_start, dst_vmap, src_vmap); if (!err) { - vma_start_read_locked(*dst_vmap); - if (*dst_vmap !=3D *src_vmap) - vma_start_read_locked_nested(*src_vmap, - SINGLE_DEPTH_NESTING); + if (vma_start_read_locked(*dst_vmap)) { + if (*dst_vmap !=3D *src_vmap) { + if (!vma_start_read_locked_nested(*src_vmap, + SINGLE_DEPTH_NESTING)) { + vma_end_read(*dst_vmap); + err =3D -EAGAIN; + } + } + } else { + err =3D -EAGAIN; + } } mmap_read_unlock(mm); return err; --=20 2.47.1.613.gc27f4b7a9f-goog