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 4D2732D0622; Fri, 28 Nov 2025 18:55:23 +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=1764356124; cv=none; b=q18Ty5FgEgTaAFLVmqCjF2y2XvwlRhxWoyerg9SFsbHrICsjVMyOImvvhw5FC8MrTiElTcORhDloqrdpdzN29wJjBAnc2jVcnbQRsGF0JvRyfGiAfAH9V0k8kjqp57dSqAQ/D25vu6nIchdZP/fCGbJXq/6f/XP7FNnZmOa7ouM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764356124; c=relaxed/simple; bh=bIPaIQFsV5dPVv4UUZ6HSMuS+/tihJQmcM7KGPYU09s=; h=Date:To:From:Subject:Message-Id; b=WtBhAbv/722cxsJUrldkE9Ui9Lf/sqfGvV3qqZbXO+6RZqWr3CEBv+LgwlbaPQewHR2PH0h9I2+/bJhAIt6IfYaVbifjrZsiT0cPYt3cp8XFj2VXfyxk+zMkOHoQy/H+XUbzAK27sMc3ftLTdGzSIrPNWW/+Obkasc8xRApmxMQ= 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=cR0YtCn3; 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="cR0YtCn3" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B995CC4CEFB; Fri, 28 Nov 2025 18:55:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1764356123; bh=bIPaIQFsV5dPVv4UUZ6HSMuS+/tihJQmcM7KGPYU09s=; h=Date:To:From:Subject:From; b=cR0YtCn39IZ3ttFZ4ZFWjp4ZtHlaOivISCx7OXo1P38xsKjyBFEMWHLDrQ4/vNTJb BGuGJnA5MSMMfSNdu3ncY/pLw9U0/GhFdGjgqOuZQAA1ffSLhS7P5EOlOx22dn3T1D CeqIyAWvxVDdtV4ro2jDN5IVLcUach/eK81OyeXc= Date: Fri, 28 Nov 2025 10:55:23 -0800 To: mm-commits@vger.kernel.org,vincenzo.frascino@arm.com,urezki@gmail.com,stable@vger.kernel.org,ryabinin.a.a@gmail.com,kees@kernel.org,glider@google.com,dvyukov@google.com,dakr@kernel.org,andreyknvl@gmail.com,jiayuan.chen@linux.dev,akpm@linux-foundation.org From: Andrew Morton Subject: + mm-kasan-fix-incorrect-unpoisoning-in-vrealloc-for-kasan.patch added to mm-hotfixes-unstable branch Message-Id: <20251128185523.B995CC4CEFB@smtp.kernel.org> Precedence: bulk X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The patch titled Subject: mm/kasan: fix incorrect unpoisoning in vrealloc for KASAN has been added to the -mm mm-hotfixes-unstable branch. Its filename is mm-kasan-fix-incorrect-unpoisoning-in-vrealloc-for-kasan.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-kasan-fix-incorrect-unpoisoning-in-vrealloc-for-kasan.patch This patch will later appear in the mm-hotfixes-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next via the mm-everything branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there every 2-3 working days ------------------------------------------------------ From: Jiayuan Chen Subject: mm/kasan: fix incorrect unpoisoning in vrealloc for KASAN Date: Fri, 28 Nov 2025 19:15:14 +0800 Syzkaller reported a memory out-of-bounds bug [1]. This patch fixes two issues: 1. In vrealloc, we were missing the KASAN_VMALLOC_VM_ALLOC flag when unpoisoning the extended region. This flag is required to correctly associate the allocation with KASAN's vmalloc tracking. Note: In contrast, vzalloc (via __vmalloc_node_range_noprof) explicitly sets KASAN_VMALLOC_VM_ALLOC and calls kasan_unpoison_vmalloc() with it. vrealloc must behave consistently — especially when reusing existing vmalloc regions — to ensure KASAN can track allocations correctly. 2. When vrealloc reuses an existing vmalloc region (without allocating new pages), KASAN previously generated a new tag, which broke tag-based memory access tracking. We now add a 'reuse_tag' parameter to __kasan_unpoison_vmalloc() to preserve the original tag in such cases. A new helper kasan_unpoison_vralloc() is introduced to handle this reuse scenario, ensuring consistent tag behavior during reallocation. Link: https://lkml.kernel.org/r/20251128111516.244497-1-jiayuan.chen@linux.dev Link: https://syzkaller.appspot.com/bug?extid=997752115a851cb0cf36 [1] Fixes: a0309faf1cb0 ("mm: vmalloc: support more granular vrealloc() sizing") Signed-off-by: Jiayuan Chen Reported-by: syzbot+997752115a851cb0cf36@syzkaller.appspotmail.com Closes: https://lore.kernel.org/all/68e243a2.050a0220.1696c6.007d.GAE@google.com/T/ Cc: Alexander Potapenko Cc: Andrey Konovalov Cc: Andrey Ryabinin Cc: Danilo Krummrich Cc: Dmitriy Vyukov Cc: Kees Cook Cc: "Uladzislau Rezki (Sony)" Cc: Vincenzo Frascino Cc: Signed-off-by: Andrew Morton --- include/linux/kasan.h | 21 +++++++++++++++++++-- mm/kasan/hw_tags.c | 4 ++-- mm/kasan/shadow.c | 6 ++++-- mm/vmalloc.c | 4 ++-- 4 files changed, 27 insertions(+), 8 deletions(-) --- a/include/linux/kasan.h~mm-kasan-fix-incorrect-unpoisoning-in-vrealloc-for-kasan +++ a/include/linux/kasan.h @@ -596,13 +596,23 @@ static inline void kasan_release_vmalloc #endif /* CONFIG_KASAN_GENERIC || CONFIG_KASAN_SW_TAGS */ void *__kasan_unpoison_vmalloc(const void *start, unsigned long size, - kasan_vmalloc_flags_t flags); + kasan_vmalloc_flags_t flags, bool reuse_tag); + +static __always_inline void *kasan_unpoison_vrealloc(const void *start, + unsigned long size, + kasan_vmalloc_flags_t flags) +{ + if (kasan_enabled()) + return __kasan_unpoison_vmalloc(start, size, flags, true); + return (void *)start; +} + static __always_inline void *kasan_unpoison_vmalloc(const void *start, unsigned long size, kasan_vmalloc_flags_t flags) { if (kasan_enabled()) - return __kasan_unpoison_vmalloc(start, size, flags); + return __kasan_unpoison_vmalloc(start, size, flags, false); return (void *)start; } @@ -629,6 +639,13 @@ static inline void kasan_release_vmalloc unsigned long free_region_end, unsigned long flags) { } +static inline void *kasan_unpoison_vrealloc(const void *start, + unsigned long size, + kasan_vmalloc_flags_t flags) +{ + return (void *)start; +} + static inline void *kasan_unpoison_vmalloc(const void *start, unsigned long size, kasan_vmalloc_flags_t flags) --- a/mm/kasan/hw_tags.c~mm-kasan-fix-incorrect-unpoisoning-in-vrealloc-for-kasan +++ a/mm/kasan/hw_tags.c @@ -317,7 +317,7 @@ static void init_vmalloc_pages(const voi } void *__kasan_unpoison_vmalloc(const void *start, unsigned long size, - kasan_vmalloc_flags_t flags) + kasan_vmalloc_flags_t flags, bool reuse_tag) { u8 tag; unsigned long redzone_start, redzone_size; @@ -361,7 +361,7 @@ void *__kasan_unpoison_vmalloc(const voi return (void *)start; } - tag = kasan_random_tag(); + tag = reuse_tag ? get_tag(start) : kasan_random_tag(); start = set_tag(start, tag); /* Unpoison and initialize memory up to size. */ --- a/mm/kasan/shadow.c~mm-kasan-fix-incorrect-unpoisoning-in-vrealloc-for-kasan +++ a/mm/kasan/shadow.c @@ -625,7 +625,7 @@ void kasan_release_vmalloc(unsigned long } void *__kasan_unpoison_vmalloc(const void *start, unsigned long size, - kasan_vmalloc_flags_t flags) + kasan_vmalloc_flags_t flags, bool reuse_tag) { /* * Software KASAN modes unpoison both VM_ALLOC and non-VM_ALLOC @@ -648,7 +648,9 @@ void *__kasan_unpoison_vmalloc(const voi !(flags & KASAN_VMALLOC_PROT_NORMAL)) return (void *)start; - start = set_tag(start, kasan_random_tag()); + if (!reuse_tag) + start = set_tag(start, kasan_random_tag()); + kasan_unpoison(start, size, false); return (void *)start; } --- a/mm/vmalloc.c~mm-kasan-fix-incorrect-unpoisoning-in-vrealloc-for-kasan +++ a/mm/vmalloc.c @@ -4175,8 +4175,8 @@ void *vrealloc_node_align_noprof(const v * We already have the bytes available in the allocation; use them. */ if (size <= alloced_size) { - kasan_unpoison_vmalloc(p + old_size, size - old_size, - KASAN_VMALLOC_PROT_NORMAL); + kasan_unpoison_vrealloc(p, size, + KASAN_VMALLOC_PROT_NORMAL | KASAN_VMALLOC_VM_ALLOC); /* * No need to zero memory here, as unused memory will have * already been zeroed at initial allocation time or during _ Patches currently in -mm which might be from jiayuan.chen@linux.dev are mm-kasan-fix-incorrect-unpoisoning-in-vrealloc-for-kasan.patch mm-vmscan-skip-increasing-kswapd_failures-when-reclaim-was-boosted.patch