From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-oo1-f79.google.com (mail-oo1-f79.google.com [209.85.161.79]) (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 9D30F2BE031 for ; Fri, 6 Feb 2026 06:43:24 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.161.79 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770360204; cv=none; b=XnYW4ouxuCp5U8fsXWWFwYecfBCw8ot/mVeAuTdP7V7q/H7rUxnOCokeXiCSiRi1mrhLLHSNM+ZTSrVSKvSua5sUIf6NO7UZVpEFJr0vADgZmkwU8WZR2T69tDazodyQQOwAyrkatP+Al3NOyxKZkPPl3IejZMeMTKSATtIKJWI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770360204; c=relaxed/simple; bh=+cO6t/lm9/k+28VlcTkIE9ZjzGYW1aFL5zWAsUWAWpY=; h=MIME-Version:Date:Message-ID:Subject:From:To:Content-Type; b=jaVq44vSXnn3KCxxSZXhRCaYwxL71q7lJp0bdfT5WKRLpxd+37aWJDwCQ0/Yo1dNr5BDqdEsTAh9R4S9wF7GOzVGSvLATZ/SHKn3tUZlt7NFQeb9GhmfuUE4GVdm9zskqrxA5+yii+GgoxZhjeSCZ3HUkzDxkFPSQ9EmIEEcwGw= 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=209.85.161.79 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-oo1-f79.google.com with SMTP id 006d021491bc7-66b8c7f0debso8492303eaf.3 for ; Thu, 05 Feb 2026 22:43:24 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1770360203; x=1770965003; h=to:from:subject:message-id:date:mime-version:x-gm-message-state :from:to:cc:subject:date:message-id:reply-to; bh=j1a5dRNKFJ6iLwot47+qs/BzICGmio9RFVJIwM5Coxo=; b=btU6giiEQOuP97km1m1pmW7GdBUEzyesM9R8Qis3H0uUGtuyxABo3xMxEMEEPkLNlc Br6KpZMoGB4M6/EAvGj/HlDd6UxDEJ8FKp+OeH9wR4FiGaa8U0vnM0rc1HnC4CzTbwyR dtfOmkO2JJea/Xrgn5py99BdXFrDrez9iUClsQwC5dvm3GWWUjXau33yUr5LW0l9EqSQ 0GM8m4jzupIxWvP3qTwtVladyAhdgFCWMta7MDdR8aR09GOyc7NNgTN7b9Y4qmUiABGO eIfuwTlLtOYPJ3RIwss8mVdhK8od4qCmi3PBOfoYyIbQVIxalssJUfQHk9nZHs4XuEMm BKWQ== X-Forwarded-Encrypted: i=1; AJvYcCXPj5R90U1i5MY7F7gGhYiemEVRC8u/wEfELX+jw/Ru5UYad9zjCLH/bek47TPuXNvH81Wf4J3rE6wt1i8=@vger.kernel.org X-Gm-Message-State: AOJu0YwII/Lcn+3qKH8AG2mdfmFJwmUjwLeltDOWUHkSkqad+bSaWL4D 1tpJKR3S9Rq8C4UmRtrDLnZHrL64sD4kXn6qDn48EWiCWsnLhDMwQF9XyKy7gLOyLU9Q5lYH0Xl +zuFYcAioNuBj46XrUg4jIAtpvapxU4bw/P0C4io6T8HyQ84wmlqvQxul0wA= Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Received: by 2002:a05:6820:998:b0:65f:66c5:c6b with SMTP id 006d021491bc7-66d099c57b9mr841928eaf.9.1770360203561; Thu, 05 Feb 2026 22:43:23 -0800 (PST) Date: Thu, 05 Feb 2026 22:43:23 -0800 X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <69858d8b.050a0220.3b3015.0031.GAE@google.com> Subject: [syzbot] [exfat?] KCSAN: data-race in fat12_ent_put / fat_mirror_bhs 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: de0674d9bc69 Merge tag 'for-6.19-rc8-tag' of git://git.ker.. git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=15f240aa580000 kernel config: https://syzkaller.appspot.com/x/.config?x=8e27f4588a0f2183 dashboard link: https://syzkaller.appspot.com/bug?extid=51b4c65bb770155d058f compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8 Unfortunately, I don't have any reproducer for this issue yet. Downloadable assets: disk image: https://storage.googleapis.com/syzbot-assets/bfedab2f6279/disk-de0674d9.raw.xz vmlinux: https://storage.googleapis.com/syzbot-assets/f012a4cb8d82/vmlinux-de0674d9.xz kernel image: https://storage.googleapis.com/syzbot-assets/acb727c49110/bzImage-de0674d9.xz IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+51b4c65bb770155d058f@syzkaller.appspotmail.com ================================================================== BUG: KCSAN: data-race in fat12_ent_put / fat_mirror_bhs read-write to 0xffff888129151032 of 1 bytes by task 4937 on cpu 1: fat12_ent_put+0xc4/0x170 fs/fat/fatent.c:165 fat_ent_write+0x6c/0xe0 fs/fat/fatent.c:417 fat_chain_add+0x16c/0x490 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+0x46c/0x5e0 fs/fat/inode.c:190 __block_write_begin_int+0x400/0xf90 fs/buffer.c:2145 block_write_begin fs/buffer.c:2256 [inline] cont_write_begin+0x5fe/0x970 fs/buffer.c:2594 fat_write_begin+0x4f/0xe0 fs/fat/inode.c:230 generic_perform_write+0x183/0x490 mm/filemap.c:4314 __generic_file_write_iter+0x9e/0x120 mm/filemap.c:4431 generic_file_write_iter+0x8d/0x310 mm/filemap.c:4457 new_sync_write fs/read_write.c:593 [inline] vfs_write+0x5a6/0x9f0 fs/read_write.c:686 ksys_write+0xdc/0x1a0 fs/read_write.c:738 __do_sys_write fs/read_write.c:749 [inline] __se_sys_write fs/read_write.c:746 [inline] __x64_sys_write+0x40/0x50 fs/read_write.c:746 x64_sys_call+0x2847/0x3000 arch/x86/include/generated/asm/syscalls_64.h:2 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xc0/0x2a0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f read to 0xffff888129151000 of 512 bytes by task 4940 on cpu 0: fat_mirror_bhs+0x1df/0x320 fs/fat/fatent.c:395 fat_alloc_clusters+0xb48/0xc50 fs/fat/fatent.c:543 fat_add_cluster fs/fat/inode.c:108 [inline] __fat_get_block fs/fat/inode.c:155 [inline] fat_get_block+0x258/0x5e0 fs/fat/inode.c:190 __block_write_begin_int+0x400/0xf90 fs/buffer.c:2145 block_write_begin fs/buffer.c:2256 [inline] cont_write_begin+0x5fe/0x970 fs/buffer.c:2594 fat_write_begin+0x4f/0xe0 fs/fat/inode.c:230 generic_perform_write+0x183/0x490 mm/filemap.c:4314 __generic_file_write_iter+0x9e/0x120 mm/filemap.c:4431 generic_file_write_iter+0x8d/0x310 mm/filemap.c:4457 __kernel_write_iter+0x319/0x590 fs/read_write.c:619 dump_emit_page fs/coredump.c:1298 [inline] dump_user_range+0xa7d/0xdb0 fs/coredump.c:1372 elf_core_dump+0x21a2/0x2330 fs/binfmt_elf.c:2111 coredump_write+0xacf/0xdf0 fs/coredump.c:1049 do_coredump fs/coredump.c:1126 [inline] vfs_coredump+0x26bc/0x3120 fs/coredump.c:1200 get_signal+0xd7b/0xf60 kernel/signal.c:3019 arch_do_signal_or_restart+0x96/0x450 arch/x86/kernel/signal.c:337 __exit_to_user_mode_loop kernel/entry/common.c:41 [inline] exit_to_user_mode_loop kernel/entry/common.c:75 [inline] __exit_to_user_mode_prepare include/linux/irq-entry-common.h:226 [inline] irqentry_exit_to_user_mode_prepare include/linux/irq-entry-common.h:270 [inline] irqentry_exit_to_user_mode include/linux/irq-entry-common.h:339 [inline] irqentry_exit+0xf7/0x510 kernel/entry/common.c:196 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:618 Reported by Kernel Concurrency Sanitizer on: CPU: 0 UID: 0 PID: 4940 Comm: syz.3.398 Not tainted syzkaller #0 PREEMPT(voluntary) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025 ================================================================== syz.3.398 (4940) used greatest stack depth: 8696 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