From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-ot1-f79.google.com (mail-ot1-f79.google.com [209.85.210.79]) (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 2ACA633B6CB for ; Wed, 12 Aug 2026 23:56:30 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.210.79 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786578992; cv=none; b=nF0iVeXYxJjUsYFph+MF2EFvFTyvFtzKB84L4hntyeZt1xPwzO7VADBjl3/CSPR94BlWzykwMMYPYYvXu3+aEsmbI6jAOp1QqA2WrurK/TzXQsgAdMkgXstVIDQ2jOJ46Eu33ACqg/z9aIANFKn0TGU/tkr9pn5OIm3A/yq+GAk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786578992; c=relaxed/simple; bh=pmVqbuYfiqTFkBbZGqyuzlVEPLnzEJOct3P0msUPe/o=; h=MIME-Version:Date:Message-ID:Subject:From:To:Content-Type; b=JjL1BC4/h9GkD5ISoTpMNkm8TG8UZ9mxqgAf8Zkw7usEBJYf9FQIuSdrjXspWiyYnlwX3GibQ9MPcyciaRZSt7Ou6DuheWorDjPrtIaNkGa3KUpci+FiePI2qfdOVzr/n2KXbLPE4ajNTjvM+4oYi9vgIeEIQH+ki8n7zrEkj4Q= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=syzkaller.appspotmail.com; spf=pass smtp.mailfrom=M3KW2WVRGUFZ5GODRSRYTGD7.apphosting.bounces.google.com; arc=none smtp.client-ip=209.85.210.79 Authentication-Results: smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=syzkaller.appspotmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=M3KW2WVRGUFZ5GODRSRYTGD7.apphosting.bounces.google.com Received: by mail-ot1-f79.google.com with SMTP id 46e09a7af769-7e6b73b3920so200089a34.0 for ; Wed, 12 Aug 2026 16:56:30 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1786578990; x=1787183790; h=content-type:to:from:subject:message-id:date:mime-version :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to :content-type; bh=+v5oTfyGF2lTff6vcwWwqW2v/d8rOItbnNCVE9cW5JY=; b=FRJZmqFRWMIeHR8X2ROuOVwJ9xshd9lKjxtiZJznOXdnWdarra4u9e+Xt4sUUeMGbE KfQO6SbrPKJg3aodQji3+bJ8lkU0/LR9i/Eb4wZ9aqCLB02VZmufrCOQUjkYh4AXnInv ElHBSz/wcWzN8QIpm7vZOtQqUUy2uLRgZPUEN+HnXIuLOhiwUhSwt3taqQFykMSpWIoh OSAywYNNVzoyFo4JI4iJZVFud3nX+J1cpbjnglEU9PH/NuKSBmUS1BpbZR01Me0Fodj5 rfDL+XDjCHqoHk+MzO9NjTeN+brx8f7je23/t9rrh0piTGMeeeFBaPiXUG9zXNDkfjKw Qocg== X-Forwarded-Encrypted: i=1; AHgh+Rqi/HW24iUd7mJrwoqu6Cx1VhDgJ3LseySTR9FdCmU2jVtsP8+ByO1LfW17vVoKNULIySxqw8tazXOEHOA=@vger.kernel.org X-Gm-Message-State: AOJu0YxKAhikI4/zP0T1R5SMUS0m3l9YEWywW2ZvGqxyNgo76QqUvG5E zona+uUjU6vWXfxK1mSFeIuZUxc5pIM3Bz5aa0ZOGCorBTvRJHwinNP5XQW1Cf1NYegCJwCpwnO pa5KSas8gdkwU7ZCjhpqFShmQ+hylGP9+2FPZCqG0bC4RyRA3+REaGoewBZI= Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Received: by 2002:a05:6820:c86:b0:6b0:4355:3c8d with SMTP id 006d021491bc7-6b0c465f18dmr2109852eaf.34.1786578990086; Wed, 12 Aug 2026 16:56:30 -0700 (PDT) Date: Wed, 12 Aug 2026 16:56:30 -0700 X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <6a7d082e.d5f0ebe7.22d851.0012.GAE@google.com> Subject: [syzbot] [exfat?] KCSAN: data-race in fat32_ent_put / fat_mirror_bhs (4) From: syzbot To: hirofumi@mail.parknet.co.jp, linkinjeon@kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, sj1557.seo@samsung.com, syzkaller-bugs@googlegroups.com Content-Type: text/plain; charset="UTF-8" Hello, syzbot found the following issue on: HEAD commit: 3d6d817622b0 Merge tag 'scsi-fixes' of git://git.kernel.or.. git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=15263225580000 kernel config: https://syzkaller.appspot.com/x/.config?x=33c5ac947f6be69e dashboard link: https://syzkaller.appspot.com/bug?extid=9435f33de7962a2cb62d compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8 Unfortunately, I don't have any reproducer for this issue yet. Downloadable assets: disk image: https://storage.googleapis.com/syzbot-assets/8a0f9e563bc1/disk-3d6d8176.raw.xz vmlinux: https://storage.googleapis.com/syzbot-assets/a3d8fcb60747/vmlinux-3d6d8176.xz kernel image: https://storage.googleapis.com/syzbot-assets/f5e1d8d94487/bzImage-3d6d8176.xz IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+9435f33de7962a2cb62d@syzkaller.appspotmail.com ================================================================== BUG: KCSAN: data-race in fat32_ent_put / fat_mirror_bhs read-write to 0xffff88811db1234c of 4 bytes by task 4861 on cpu 1: fat32_ent_put+0x4e/0x90 fs/fat/fatent.c:194 fat_ent_write+0x6c/0xe0 fs/fat/fatent.c:422 fat_chain_add+0x174/0x4a0 fs/fat/misc.c:136 fat_add_cluster fs/fat/inode.c:113 [inline] __fat_get_block fs/fat/inode.c:155 [inline] fat_get_block+0x468/0x5e0 fs/fat/inode.c:190 __block_write_begin_int+0x400/0xf90 fs/buffer.c:2123 block_write_begin fs/buffer.c:2234 [inline] cont_write_begin+0x5bf/0x920 fs/buffer.c:2596 fat_write_begin+0x52/0xe0 fs/fat/inode.c:230 cont_expand_zero fs/buffer.c:2524 [inline] cont_write_begin+0x18d/0x920 fs/buffer.c:2586 fat_write_begin+0x52/0xe0 fs/fat/inode.c:230 generic_cont_expand_simple+0xb0/0x150 fs/buffer.c:2487 fat_cont_expand+0x3e/0x170 fs/fat/file.c:227 fat_fallocate+0x177/0x1c0 fs/fat/file.c:305 vfs_fallocate+0x3ac/0x400 fs/open.c:338 ksys_fallocate fs/open.c:362 [inline] __do_sys_fallocate fs/open.c:367 [inline] __se_sys_fallocate fs/open.c:365 [inline] __x64_sys_fallocate+0x7a/0xd0 fs/open.c:365 x64_sys_call+0x298e/0x3020 arch/x86/include/generated/asm/syscalls_64.h:286 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 0xffff88811db12000 of 2048 bytes by task 4866 on cpu 0: fat_mirror_bhs+0x1df/0x330 fs/fat/fatent.c:399 fat_ent_write+0xd0/0xe0 fs/fat/fatent.c:428 fat_chain_add+0x174/0x4a0 fs/fat/misc.c:136 fat_add_cluster fs/fat/inode.c:113 [inline] __fat_get_block fs/fat/inode.c:155 [inline] fat_get_block+0x468/0x5e0 fs/fat/inode.c:190 __block_write_begin_int+0x400/0xf90 fs/buffer.c:2123 block_write_begin fs/buffer.c:2234 [inline] cont_write_begin+0x5bf/0x920 fs/buffer.c:2596 fat_write_begin+0x52/0xe0 fs/fat/inode.c:230 generic_perform_write+0x186/0x490 mm/filemap.c:4364 __generic_file_write_iter+0x9e/0x120 mm/filemap.c:4481 generic_file_write_iter+0x77/0x1f0 mm/filemap.c:4507 __kernel_write_iter+0x30f/0x590 fs/read_write.c:621 dump_emit_page fs/coredump.c:1298 [inline] dump_user_range+0xa73/0xd00 fs/coredump.c:1372 elf_core_dump+0x21c0/0x2340 fs/binfmt_elf.c:2109 coredump_write+0xaf9/0xdd0 fs/coredump.c:1052 do_coredump fs/coredump.c:1131 [inline] vfs_coredump+0x2770/0x3290 fs/coredump.c:1200 get_signal+0xd33/0xf10 kernel/signal.c:3031 arch_do_signal_or_restart+0x96/0x480 arch/x86/kernel/signal.c:337 __exit_to_user_mode_loop kernel/entry/common.c:66 [inline] exit_to_user_mode_loop kernel/entry/common.c:101 [inline] __exit_to_user_mode_prepare include/linux/irq-entry-common.h:207 [inline] irqentry_exit_to_user_mode_prepare include/linux/irq-entry-common.h:244 [inline] irqentry_exit_to_user_mode include/linux/irq-entry-common.h:315 [inline] irqentry_exit+0x14d/0x610 kernel/entry/common.c:165 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:595 Reported by Kernel Concurrency Sanitizer on: CPU: 0 UID: 0 PID: 4866 Comm: syz.3.376 Not tainted syzkaller #0 PREEMPT(lazy) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026 ================================================================== syz.3.376 (4866) used greatest stack depth: 9320 bytes left --- 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