From nobody Fri Dec 19 16:01:04 2025 Received: from mail-10629.protonmail.ch (mail-10629.protonmail.ch [79.135.106.29]) (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 9B5253612FA for ; Wed, 17 Dec 2025 13:50:18 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=79.135.106.29 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1765979420; cv=none; b=VZKpRtwjyUzOMH8IYzGel3fhUtQzblYDRV59AhavC5hwU1woDFY/xEpxekx8R0piiKjdfd8Pkywxhce6bEa4BZnjFAWqjM6bgzFxSh0aJYloa/d/S0S+zRtgRabU//EXAhrxL5zbcu+GQ5f/sSORboqAoeAZy4PNP+2YKGixuoo= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1765979420; c=relaxed/simple; bh=56gSMlNSR750g1EMqQBT9133w6XPsBj5vvvp7jvOjf4=; h=Date:To:From:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=UGIWi2ldpJQw1dSLbQf0eWe7OenM6GrfI5ENtZFm3WBBOKXfw/iw88W3H1cKE/PMUTAN61ekichuV8z+JP8zg8sVeRPqi1qutHcrDsMFVRiRmBaCZDxn5X2OU3b2MUlFCmyuVJA04gFUGqK6ERXd0XQWmP9eM8DWJTciQzZ6e5Q= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=pm.me; spf=pass smtp.mailfrom=pm.me; dkim=pass (2048-bit key) header.d=pm.me header.i=@pm.me header.b=O35IO7JW; arc=none smtp.client-ip=79.135.106.29 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=pm.me Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=pm.me Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=pm.me header.i=@pm.me header.b="O35IO7JW" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=pm.me; s=protonmail3; t=1765979411; x=1766238611; bh=srKF/LsI6PPbEJ2JymYTvJSPX0AgbkVbHs9iEZzuI9A=; h=Date:To:From:Cc:Subject:Message-ID:In-Reply-To:References: Feedback-ID:From:To:Cc:Date:Subject:Reply-To:Feedback-ID: Message-ID:BIMI-Selector; b=O35IO7JW/ro9Jo8gR76XtYsxZThKfr0wv14Xf93ZZNdm7fklI0t3DdCmInY/3tj0m 6iyJ2bz4kGSuHW4vOklie4rrCp9WCRHhBwrhNXBTyvOjrHEX34r2ffDwZEMUsiK440 Uy4krURxA7opcMjfqwegJCepZhKXv02ZjxXYouhemmHKkAR028XeZwldhMckqoG1jQ 8GGYyVqU/fPPmdt9oHhVi4Vczrh//kR8B9N0bOlbinBbBR60skGONF7OSnodssABEa LgBXe4u0xchn12axhs42phx9Op9DETtbmIEPlqN6dIB7UYUc+dgInkDnyPgtFKSAEY setwGfGp3dOcw== Date: Wed, 17 Dec 2025 13:50:05 +0000 To: Andrey Ryabinin , Alexander Potapenko , Andrey Konovalov , Dmitry Vyukov , Vincenzo Frascino , Andrew Morton , Uladzislau Rezki , Kees Cook , Danilo Krummrich From: Maciej Wieczor-Retman Cc: m.wieczorretman@pm.me, stable@vger.kernel.org, syzbot+997752115a851cb0cf36@syzkaller.appspotmail.com, Jiayuan Chen , Maciej Wieczor-Retman , kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH v5 1/3] mm/kasan: Fix incorrect unpoisoning in vrealloc for KASAN Message-ID: <3f851f7704ab8468530f384b901b22cdef94aa43.1765978969.git.m.wieczorretman@pm.me> In-Reply-To: References: Feedback-ID: 164464600:user:proton X-Pm-Message-ID: 0bc86e18ec967a34de1512b770ea99c717647150 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Jiayuan Chen Syzkaller reported a memory out-of-bounds bug [1]. This patch fixes two issues: 1. In vrealloc the KASAN_VMALLOC_VM_ALLOC flag is missing 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 =E2=80=94 especially when reusing exis= ting vmalloc regions =E2=80=94 to ensure KASAN can track allocations correctl= y. 2. When vrealloc reuses an existing vmalloc region (without allocating new pages) KASAN generates a new tag, which breaks tag-based memory access tracking. Introduce KASAN_VMALLOC_KEEP_TAG, a new KASAN flag that allows reusing the tag already attached to the pointer, ensuring consistent tag behavior during reallocation. Pass KASAN_VMALLOC_KEEP_TAG and KASAN_VMALLOC_VM_ALLOC to the kasan_unpoison_vmalloc inside vrealloc_node_align_noprof(). [1]: https://syzkaller.appspot.com/bug?extid=3D997752115a851cb0cf36 Fixes: a0309faf1cb0 ("mm: vmalloc: support more granular vrealloc() sizing") Cc: Reported-by: syzbot+997752115a851cb0cf36@syzkaller.appspotmail.com Closes: https://lore.kernel.org/all/68e243a2.050a0220.1696c6.007d.GAE@googl= e.com/T/ Signed-off-by: Jiayuan Chen Co-developed-by: Maciej Wieczor-Retman Signed-off-by: Maciej Wieczor-Retman Reviewed-by: Andrey Konovalov --- include/linux/kasan.h | 1 + mm/kasan/hw_tags.c | 2 +- mm/kasan/shadow.c | 4 +++- mm/vmalloc.c | 4 +++- 4 files changed, 8 insertions(+), 3 deletions(-) diff --git a/include/linux/kasan.h b/include/linux/kasan.h index f335c1d7b61d..df3d8567dde9 100644 --- a/include/linux/kasan.h +++ b/include/linux/kasan.h @@ -28,6 +28,7 @@ typedef unsigned int __bitwise kasan_vmalloc_flags_t; #define KASAN_VMALLOC_INIT ((__force kasan_vmalloc_flags_t)0x01u) #define KASAN_VMALLOC_VM_ALLOC ((__force kasan_vmalloc_flags_t)0x02u) #define KASAN_VMALLOC_PROT_NORMAL ((__force kasan_vmalloc_flags_t)0x04u) +#define KASAN_VMALLOC_KEEP_TAG ((__force kasan_vmalloc_flags_t)0x08u) =20 #define KASAN_VMALLOC_PAGE_RANGE 0x1 /* Apply exsiting page range */ #define KASAN_VMALLOC_TLB_FLUSH 0x2 /* TLB flush */ diff --git a/mm/kasan/hw_tags.c b/mm/kasan/hw_tags.c index 1c373cc4b3fa..cbef5e450954 100644 --- a/mm/kasan/hw_tags.c +++ b/mm/kasan/hw_tags.c @@ -361,7 +361,7 @@ void *__kasan_unpoison_vmalloc(const void *start, unsig= ned long size, return (void *)start; } =20 - tag =3D kasan_random_tag(); + tag =3D (flags & KASAN_VMALLOC_KEEP_TAG) ? get_tag(start) : kasan_random_= tag(); start =3D set_tag(start, tag); =20 /* Unpoison and initialize memory up to size. */ diff --git a/mm/kasan/shadow.c b/mm/kasan/shadow.c index 29a751a8a08d..32fbdf759ea2 100644 --- a/mm/kasan/shadow.c +++ b/mm/kasan/shadow.c @@ -631,7 +631,9 @@ void *__kasan_unpoison_vmalloc(const void *start, unsig= ned long size, !(flags & KASAN_VMALLOC_PROT_NORMAL)) return (void *)start; =20 - start =3D set_tag(start, kasan_random_tag()); + if (unlikely(!(flags & KASAN_VMALLOC_KEEP_TAG))) + start =3D set_tag(start, kasan_random_tag()); + kasan_unpoison(start, size, false); return (void *)start; } diff --git a/mm/vmalloc.c b/mm/vmalloc.c index ecbac900c35f..94c0a9262a46 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -4331,7 +4331,9 @@ void *vrealloc_node_align_noprof(const void *p, size_= t size, unsigned long align */ if (size <=3D alloced_size) { kasan_unpoison_vmalloc(p + old_size, size - old_size, - KASAN_VMALLOC_PROT_NORMAL); + KASAN_VMALLOC_PROT_NORMAL | + KASAN_VMALLOC_VM_ALLOC | + KASAN_VMALLOC_KEEP_TAG); /* * No need to zero memory here, as unused memory will have * already been zeroed at initial allocation time or during --=20 2.52.0