From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 B26AF3BA232 for ; Mon, 22 Jun 2026 15:35:56 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782142557; cv=none; b=TfxstxOw93fRlXHvNOI29xkWDsyikwk8y56VHx0x6oBOZkCvZ7pIzCejKSSkY5pE1j+qZsPVVPaQkqB5+ZudhsdlkkvNmgNFkFvNPEpbFId7mEkdIzK4K9I9T9PCu/Aj2EymRN1vOrWdhtoWYpPlEmYDAp3eybiSExugHesH2zg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782142557; c=relaxed/simple; bh=7jiD7YesxsGTXtYTpphWhC3E+uDJCrDy7Fv0B46Fsko=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=RhNnDaZFTbc3urDtrVHXsczXzmvN9AUbCkXb+H2rLLZguV73wY3Gy2vdTpA5xXIUQlXesYLPSJ+stS8TVZXDn0p2tAx+xBJUf6MjgJ6Gj+u6vXidQK22DYcPx+lroCUfMJlm5F2VWqwkZCqEjidxEmdLyvarxaOX2fEPNXJIKxw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=bm3nPm2O; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="bm3nPm2O" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9ED841F000E9; Mon, 22 Jun 2026 15:35:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1782142556; bh=0WtLG98RNnKThawH5sUjIfrTNwRKeoy4IoR8MM6IZeM=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=bm3nPm2OEqpyPhkbTQukjlslEjjjzb9GXulYKsW+0km8iovMQnS2ZV7UFAr1RwNRU 50/uyBhq8+2HhCUFyPqxOSSAsx9XBysNH1LSilW9P99isdxTKggOiXkDOCJhCVaeD5 sG8OZmlkVd/riVH7sleThbqYcjU8R7BTbo+MJ9d+XNJNAiNGLe7PSXEXY8R8y3ou+w Nfyuk//VrrmI4nZmqAaRRid9fuaOc3IWv+yin6gXlO4nsFUM7uoIOrTpH6opUTLMr6 kYp84VC+4lo5ZNxV647bAgnH3L+N6CNki4x0Qju4J1clqK+Fb8As8T9Tt5rWps6zKR R4r6SAzClYH3g== Date: Mon, 22 Jun 2026 16:35:49 +0100 From: Lorenzo Stoakes To: syzbot Cc: akpm@linux-foundation.org, david@kernel.org, harry@kernel.org, jannh@google.com, liam@infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, riel@surriel.com, syzkaller-bugs@googlegroups.com, vbabka@kernel.org Subject: Re: [syzbot] [mm?] KCSAN: data-race in __anon_vma_prepare / __vmf_anon_prepare (2) Message-ID: References: <6a35fcb0.6813c476.3c3d96.0003.GAE@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <6a35fcb0.6813c476.3c3d96.0003.GAE@google.com> This seems to be pretty much identical to the previous report, which we concluded was benign [0]. I think I'll send a patch to add a data_race() annotation nto the read-side. [0]:https://lore.kernel.org/linux-mm/6967c517.050a0220.150504.0007.GAE@google.com/ On Fri, Jun 19, 2026 at 07:36:32PM -0700, syzbot wrote: > Hello, > > syzbot found the following issue on: > > HEAD commit: 5e2e14749c3d Merge tag 'landlock-7.2-rc1' of git://git.ker.. > git tree: upstream > console output: https://syzkaller.appspot.com/x/log.txt?x=10e5ccfe580000 > kernel config: https://syzkaller.appspot.com/x/.config?x=b0ae27ce66b92956 > dashboard link: https://syzkaller.appspot.com/bug?extid=395b7abe9696862fc188 > compiler: Debian clang version 22.1.6 (++20260514074242+fc4aad7b5db3-1~exp1~20260514074407.73), Debian LLD 22.1.6 > > Unfortunately, I don't have any reproducer for this issue yet. > > Downloadable assets: > disk image: https://storage.googleapis.com/syzbot-assets/a565c60a4762/disk-5e2e1474.raw.xz > vmlinux: https://storage.googleapis.com/syzbot-assets/e593a6eb0057/vmlinux-5e2e1474.xz > kernel image: https://storage.googleapis.com/syzbot-assets/d24b55020ea3/bzImage-5e2e1474.xz > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > Reported-by: syzbot+395b7abe9696862fc188@syzkaller.appspotmail.com > > ================================================================== > BUG: KCSAN: data-race in __anon_vma_prepare / __vmf_anon_prepare > > write to 0xffff88811a6a4d00 of 8 bytes by task 20911 on cpu 1: > __anon_vma_prepare+0x172/0x2f0 mm/rmap.c:212 WRITE: VMA under mmap read lock, page_table_lock: vma->anon_vma = anon_vma; > __vmf_anon_prepare+0x91/0x100 mm/memory.c:3829 > hugetlb_no_page+0x1b8/0xf30 mm/hugetlb.c:5756 > hugetlb_fault+0x608/0xda0 mm/hugetlb.c:-1 > handle_mm_fault+0x1de9/0x2da0 mm/memory.c:6684 > faultin_page mm/gup.c:1126 [inline] > __get_user_pages+0x129c/0x1f10 mm/gup.c:1428 > populate_vma_page_range mm/gup.c:1860 [inline] > __mm_populate+0x242/0x390 mm/gup.c:1963 > mm_populate include/linux/mm.h:4171 [inline] > vm_mmap_pgoff+0x23b/0x2d0 mm/util.c:586 > ksys_mmap_pgoff+0x2c6/0x310 mm/mmap.c:606 > x64_sys_call+0x14df/0x3020 arch/x86/include/generated/asm/syscalls_64.h:10 > do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] > do_syscall_64+0x136/0x3c0 arch/x86/entry/syscall_64.c:94 > entry_SYSCALL_64_after_hwframe+0x77/0x7f > > read to 0xffff88811a6a4d00 of 8 bytes by task 20901 on cpu 0: > __vmf_anon_prepare+0x26/0x100 mm/memory.c:3823 READ: VMA under VMA read lock: if (likely(vma->anon_vma)) return 0; It's benign because if we race here we'd just recheck in __anon_vma_prepare() and the mm->page_table_lock would serialise for us. > hugetlb_no_page+0x1b8/0xf30 mm/hugetlb.c:5756 > hugetlb_fault+0x608/0xda0 mm/hugetlb.c:-1 > handle_mm_fault+0x1de9/0x2da0 mm/memory.c:6684 > do_user_addr_fault+0x402/0x1060 arch/x86/mm/fault.c:1394 > handle_page_fault arch/x86/mm/fault.c:1483 [inline] > exc_page_fault+0x62/0xa0 arch/x86/mm/fault.c:1536 > asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:595 > __put_user_nocheck_4+0x3/0x20 arch/x86/lib/putuser.S:97 > ____sys_recvmsg+0x1a1/0x280 net/socket.c:2917 > ___sys_recvmsg+0x11f/0x3a0 net/socket.c:2946 > do_recvmmsg+0x1e5/0x560 net/socket.c:3041 > __sys_recvmmsg net/socket.c:3115 [inline] > __do_sys_recvmmsg net/socket.c:3138 [inline] > __se_sys_recvmmsg net/socket.c:3131 [inline] > __x64_sys_recvmmsg+0xe5/0x170 net/socket.c:3131 > x64_sys_call+0x80f/0x3020 arch/x86/include/generated/asm/syscalls_64.h:300 > do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] > do_syscall_64+0x136/0x3c0 arch/x86/entry/syscall_64.c:94 > entry_SYSCALL_64_after_hwframe+0x77/0x7f > > value changed: 0x0000000000000000 -> 0xffff8881020cec60 > > Reported by Kernel Concurrency Sanitizer on: > CPU: 0 UID: 0 PID: 20901 Comm: syz.0.4316 Tainted: G W syzkaller #0 PREEMPT(lazy) > Tainted: [W]=WARN > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026 > ================================================================== > > > --- > This report is generated by a bot. It may contain errors. > See https://goo.gl/tpsmEJ for more information about syzbot. > syzbot engineers can be reached at syzkaller@googlegroups.com. > > syzbot will keep track of this issue. See: > https://goo.gl/tpsmEJ#status for how to communicate with syzbot. > > If the report is already addressed, let syzbot know by replying with: > #syz fix: exact-commit-title > > If you want to overwrite report's subsystems, reply with: > #syz set subsystems: new-subsystem > (See the list of subsystem names on the web dashboard) > > If the report is a duplicate of another one, reply with: > #syz dup: exact-subject-of-another-report > > If you want to undo deduplication, reply with: > #syz undup Thanks, Lorenzo