From nobody Mon Feb 9 03:11:25 2026 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 B3C4B812 for ; Wed, 20 Mar 2024 00:15:47 +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=1710893749; cv=none; b=FGsGa6HgCZBA+LrXd/HjBXMxniFOdbb4b1QmtZtNL689qm63sfl4cuYjrr+RKHkhrO3l8Wtv04buJCIpu4eyqpECUyImpuKiRT/RwSAk3tRuhoPuxRywp79aSatdRFWQB5LKp2LDPB/kUaa8qjZ5jft5w4HX2z1f81oayf70X9M= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1710893749; c=relaxed/simple; bh=YyvaQnQJdiY8Q7R4CiMT+UezwhRShOi5cPHWawz2f9s=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=liQClu3iyTuzo7sgUT/iTU89HwOaQln5S1cpgEeQUKCEZZ0ot1uADdAqkHuv28AhQghhNmPfN1cEPHi/DnmTUIOtWRPrWXyiSheD3TqG066QLFbDCRU3c31GTkLlwQZYdvXI51NrmZI4KV4ydBHP5nBqmPmOdmm4ShynJfrmem0= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=dft+e1h4; 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--seanjc.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="dft+e1h4" Received: by mail-yw1-f201.google.com with SMTP id 00721157ae682-60a2b53b99eso133896307b3.3 for ; Tue, 19 Mar 2024 17:15:47 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1710893746; x=1711498546; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:reply-to:from:to:cc:subject:date:message-id:reply-to; bh=i9kVuQFqGWveMSm1GQ8GItZlMlvWOz6Hx+yWjI9J9D0=; b=dft+e1h4Nh8crW2PYZK9Wc/PQ3LW8gKEhxHBn0x64lcmPtwmgTIW21PgdkJ5S42sS/ Pmlcadj0i4zwmPC1fx5sFT3boRtHkaV3jogEkosH/84RWf1nGwB9Sr6xtk3vHuO2dmLO WNyCeHEgy/5Be4Tl9LzRkX1AuVXcnAGwhsw2ezspFv0MFKQavvxySNpZzQlAmF6KbhQu JF46oCgdu5DbrC3IbFadILDqW6xUnfXjqw6zcBY40NCxmm8ey6DUaQkgvLXPIYnesBEL UUfbP8gv/yVvEyBij/bRHX3ejd96LVCEv79BVUyBaTKGlaP4EL8eAHlEtuk9DHgIlTGu DzEA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1710893746; x=1711498546; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:reply-to:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=i9kVuQFqGWveMSm1GQ8GItZlMlvWOz6Hx+yWjI9J9D0=; b=Q6IV4GpWMXp+NtHQz/y160zDyMv/HphZdbIKRDM/QgStMmv4gwKxbjotnzosObdkED Sy4zbnuBOiPsL1xBTQJxdkEfTHmyq9o+yDIJ0oBDCLTvzYRRXRIAUvk02hv/k1gMpOB3 zpzSlmboRrQaJw6Orx+hArIiq/jeX/DQI8Cxnk8cqrq02/bPF4j3D22HvVdRO6vItFRu hzHxGXFFBXgvPFXmTL6FsXjz4lnRdSD4J0rmvrwXKRs/08CbORDgFbol5bsoOLj0oLlT zy5ZRayF45a31qRIiNmFUy/jNqb6PGyQgjGZEcphh79DknUR57IyFE5Aov8yDPQCy7kM wspg== X-Forwarded-Encrypted: i=1; AJvYcCVS3QNVShqpKBPtrilvfbvZj9vbPN/XNL/K+mdwNDqAynAZ2Wm5fGY/xhFqIG0ifdYNNA/wq4oCaQttpgf+Z4zF0MkeSDSaWZs53iH6 X-Gm-Message-State: AOJu0Yx6XBSwQRpzFricB7nSyBhRWrHLEIAAPbfL8Yg0Va2HKYc7EA7H znA9JwGHdY5lcqpfogCwQcCkFIs23gf+yWa0yf5g0r+HtFeygyfImOwuY0FDVaBtC13RGjonOso FFw== X-Google-Smtp-Source: AGHT+IF0fWCYk6aKjKkWi7E/zeckbR9RpV3kVXyudQGGVegRGO/dQ5GmRozoHp9hQmE7pRVxq/v7aqYk34A= X-Received: from zagreus.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:5c37]) (user=seanjc job=sendgmr) by 2002:a05:6902:1507:b0:dcd:ad52:6932 with SMTP id q7-20020a056902150700b00dcdad526932mr4330305ybu.5.1710893746735; Tue, 19 Mar 2024 17:15:46 -0700 (PDT) Reply-To: Sean Christopherson Date: Tue, 19 Mar 2024 17:15:40 -0700 In-Reply-To: <20240320001542.3203871-1-seanjc@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20240320001542.3203871-1-seanjc@google.com> X-Mailer: git-send-email 2.44.0.291.gc1ea87d7ee-goog Message-ID: <20240320001542.3203871-2-seanjc@google.com> Subject: [PATCH 1/3] KVM: Add helpers to consolidate gfn_to_pfn_cache's page split check From: Sean Christopherson To: Paolo Bonzini Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Sean Christopherson , syzbot+106a4f72b0474e1d1b33@syzkaller.appspotmail.com, David Woodhouse , Paul Durrant Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Add a helper to check that the incoming length for a gfn_to_pfn_cache is valid with respect to the cache's GPA and/or HVA. To avoid activating a cache with a bogus GPA, a future fix will fork the page split check in the inner refresh path into activate() and the public rerfresh() APIs, at which point KVM will check the length in three separate places. Deliberately keep the "page offset" logic open coded, as the only other path that consumes the offset, __kvm_gpc_refresh(), already needs to differentiate between GPA-based and HVA-based caches, and it's not obvious that using a helper is a net positive in overall code readability. Note, for GPA-based caches, this has a subtle side effect of using the GPA instead of the resolved HVA in the check() path, but that should be a nop as the HVA offset is derived from the GPA, i.e. the two offsets are identical, barring a KVM bug. Signed-off-by: Sean Christopherson Reviewed-by: David Woodhouse Reviewed-by: Paul Durrant --- virt/kvm/pfncache.c | 27 +++++++++++++++++++-------- 1 file changed, 19 insertions(+), 8 deletions(-) diff --git a/virt/kvm/pfncache.c b/virt/kvm/pfncache.c index 4e07112a24c2..8f2121b5f2a0 100644 --- a/virt/kvm/pfncache.c +++ b/virt/kvm/pfncache.c @@ -57,6 +57,19 @@ void gfn_to_pfn_cache_invalidate_start(struct kvm *kvm, = unsigned long start, spin_unlock(&kvm->gpc_lock); } =20 +static bool kvm_gpc_is_valid_len(gpa_t gpa, unsigned long uhva, + unsigned long len) +{ + unsigned long offset =3D kvm_is_error_gpa(gpa) ? offset_in_page(uhva) : + offset_in_page(gpa); + + /* + * The cached access must fit within a single page. The 'len' argument + * to activate() and refresh() exists only to enforce that. + */ + return offset + len <=3D PAGE_SIZE; +} + bool kvm_gpc_check(struct gfn_to_pfn_cache *gpc, unsigned long len) { struct kvm_memslots *slots =3D kvm_memslots(gpc->kvm); @@ -74,7 +87,7 @@ bool kvm_gpc_check(struct gfn_to_pfn_cache *gpc, unsigned= long len) if (kvm_is_error_hva(gpc->uhva)) return false; =20 - if (offset_in_page(gpc->uhva) + len > PAGE_SIZE) + if (!kvm_gpc_is_valid_len(gpc->gpa, gpc->uhva, len)) return false; =20 if (!gpc->valid) @@ -247,13 +260,7 @@ static int __kvm_gpc_refresh(struct gfn_to_pfn_cache *= gpc, gpa_t gpa, unsigned l if (WARN_ON_ONCE(kvm_is_error_gpa(gpa) =3D=3D kvm_is_error_hva(uhva))) return -EINVAL; =20 - /* - * The cached acces must fit within a single page. The 'len' argument - * exists only to enforce that. - */ - page_offset =3D kvm_is_error_gpa(gpa) ? offset_in_page(uhva) : - offset_in_page(gpa); - if (page_offset + len > PAGE_SIZE) + if (!kvm_gpc_is_valid_len(gpa, uhva, len)) return -EINVAL; =20 lockdep_assert_held(&gpc->refresh_lock); @@ -270,6 +277,8 @@ static int __kvm_gpc_refresh(struct gfn_to_pfn_cache *g= pc, gpa_t gpa, unsigned l old_uhva =3D PAGE_ALIGN_DOWN(gpc->uhva); =20 if (kvm_is_error_gpa(gpa)) { + page_offset =3D offset_in_page(uhva); + gpc->gpa =3D INVALID_GPA; gpc->memslot =3D NULL; gpc->uhva =3D PAGE_ALIGN_DOWN(uhva); @@ -279,6 +288,8 @@ static int __kvm_gpc_refresh(struct gfn_to_pfn_cache *g= pc, gpa_t gpa, unsigned l } else { struct kvm_memslots *slots =3D kvm_memslots(gpc->kvm); =20 + page_offset =3D offset_in_page(gpa); + if (gpc->gpa !=3D gpa || gpc->generation !=3D slots->generation || kvm_is_error_hva(gpc->uhva)) { gfn_t gfn =3D gpa_to_gfn(gpa); --=20 2.44.0.291.gc1ea87d7ee-goog