From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0BCB51E7C1C for ; Sat, 2 Aug 2025 18:54:24 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1754160864; cv=none; b=BWkbR3QiAXFWZ0pQDDTxwmwQXg3QU8qXD5Exr4tQw9ohWTwCwSznoKzTwyn6Qqo29YiHQISXXzy+ZEbbnUk1nSnIJ2vpzoiO6JXWg+ilU9NghEIWYC8Wq7462c6wfHoG7dt5KXBgkK8mQ/h0rzAMqGsO4LUap3OmqIZenFRa32g= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1754160864; c=relaxed/simple; bh=Ftkv2ucrMMcMVlaqfQ6xZat1x1RkhcgUjwQbw80cWRU=; h=Date:To:From:Subject:Message-Id; b=K2N/WpYCVl3DVS+mEtJswux/C5OXeI8dlJaey0gtsjobfcQQIvcCl8eigpXaS5ZYz9owXiatV7BGajuuyjPoxPNEtJcNgolBuFij3VUFPyH/wLvIMgN3WiaGGW1IrJ0bUnLLBsNfBES+k4S3YMG0Fj/PJwQy5uqpp1trBW07eGs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=0HjKEJvF; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="0HjKEJvF" Received: by smtp.kernel.org (Postfix) with ESMTPSA id CBA4CC4CEEF; Sat, 2 Aug 2025 18:54:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1754160863; bh=Ftkv2ucrMMcMVlaqfQ6xZat1x1RkhcgUjwQbw80cWRU=; h=Date:To:From:Subject:From; b=0HjKEJvFiaP++7TxibCiocCDXrOVtpibb0vTuiwJIa3eB8Tb4PA2XR5FkG4Fn6d97 w289alWm0mP+RqFVmvucV6jf2iCZRJSJTmykfcwhmGgtej/6zZaLoPseTgksIYE1LL LqXiRauMynccX0rvzwPLU1/ji1E2K3ks2BlXT0pA= Date: Sat, 02 Aug 2025 11:54:23 -0700 To: mm-commits@vger.kernel.org,vbabka@suse.cz,riel@surriel.com,lorenzo.stoakes@oracle.com,liam.howlett@oracle.com,harry.yoo@oracle.com,david@redhat.com,jannh@google.com,akpm@linux-foundation.org From: Andrew Morton Subject: [merged mm-stable] mm-rmap-add-anon_vma-lifetime-debug-check.patch removed from -mm tree Message-Id: <20250802185423.CBA4CC4CEEF@smtp.kernel.org> Precedence: bulk X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The quilt patch titled Subject: mm/rmap: add anon_vma lifetime debug check has been removed from the -mm tree. Its filename was mm-rmap-add-anon_vma-lifetime-debug-check.patch This patch was dropped because it was merged into the mm-stable branch of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm ------------------------------------------------------ From: Jann Horn Subject: mm/rmap: add anon_vma lifetime debug check Date: Fri, 25 Jul 2025 14:16:24 +0200 If an anon folio is mapped into userspace, its anon_vma must be alive, otherwise rmap walks can hit UAF. There have been syzkaller reports a few months ago[1][2] of UAF in rmap walks that seems to indicate that there can be pages with elevated mapcount whose anon_vma has already been freed, but I think we never figured out what the cause is; and syzkaller only hit these UAFs when memory pressure randomly caused reclaim to rmap-walk the affected pages, so it of course didn't manage to create a reproducer. Add a VM_WARN_ON_FOLIO() when we add/remove mappings of anonymous folios to hopefully catch such issues more reliably. [1] https://lore.kernel.org/r/67abaeaf.050a0220.110943.0041.GAE@google.com [2] https://lore.kernel.org/r/67a76f33.050a0220.3d72c.0028.GAE@google.com Link: https://lkml.kernel.org/r/20250725-anonvma-uaf-debug-v2-1-bc3c7e5ba5b1@google.com Signed-off-by: Jann Horn Acked-by: David Hildenbrand Reviewed-by: Lorenzo Stoakes Acked-by: Vlastimil Babka Acked-by: Harry Yoo Cc: David Hildenbrand Cc: Jann Horn Cc: Liam Howlett Cc: Rik van Riel Signed-off-by: Andrew Morton --- include/linux/rmap.h | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) --- a/include/linux/rmap.h~mm-rmap-add-anon_vma-lifetime-debug-check +++ a/include/linux/rmap.h @@ -449,6 +449,28 @@ static inline void __folio_rmap_sanity_c default: VM_WARN_ON_ONCE(true); } + + /* + * Anon folios must have an associated live anon_vma as long as they're + * mapped into userspace. + * Note that the atomic_read() mainly does two things: + * + * 1. In KASAN builds with CONFIG_SLUB_RCU_DEBUG, it causes KASAN to + * check that the associated anon_vma has not yet been freed (subject + * to KASAN's usual limitations). This check will pass if the + * anon_vma's refcount has already dropped to 0 but an RCU grace + * period hasn't passed since then. + * 2. If the anon_vma has not yet been freed, it checks that the + * anon_vma still has a nonzero refcount (as opposed to being in the + * middle of an RCU delay for getting freed). + */ + if (folio_test_anon(folio) && !folio_test_ksm(folio)) { + unsigned long mapping = (unsigned long)folio->mapping; + struct anon_vma *anon_vma; + + anon_vma = (void *)(mapping - FOLIO_MAPPING_ANON); + VM_WARN_ON_FOLIO(atomic_read(&anon_vma->refcount) == 0, folio); + } } /* _ Patches currently in -mm which might be from jannh@google.com are kasan-test-fix-protection-against-compiler-elision.patch kasan-add-test-for-slab_typesafe_by_rcu-quarantine-skipping.patch kasan-add-test-for-slab_typesafe_by_rcu-quarantine-skipping-v2.patch