From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-oi1-f205.google.com (mail-oi1-f205.google.com [209.85.167.205]) (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 F3B6B2AE7A for ; Fri, 3 Jul 2026 00:49:29 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.167.205 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783039771; cv=none; b=qC0lCLGwYK5/ppNzieyWJhrsjGlybfG/5kEv/kb60YLDMR+iK/PsYlbOzXK/ODKd3uWNI0CD+WhRSG6BZ8Gy3X+vfxTZDfTYySs/xmOG8XuPmttmMRnOLaWi4TssyANjfBEhCzPxWY9tL8Q1q6xTRGCxBWWXesA53RpagplSHGM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783039771; c=relaxed/simple; bh=zfkKAi23sFHuTQtbw/16iaKd/hbewsaa/oEMWcA8IR8=; h=MIME-Version:Date:Message-ID:Subject:From:To:Content-Type; b=c0Dywlxc2LHHoAVbRzCf/21pGB5/vkF0Z7CY9aZjFkVhRsTJoooagIQ4U9Ilwug9rBvryXZwE0zE5BoHFsJFzE2j0zWrV/XDdKuOsEijCPmoDPOfAxjugxHQTrgTo9OMADmuGHsmc16ri5/NkowxqKhDRWH9GPvheAxLJVJA2PE= 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=209.85.167.205 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-oi1-f205.google.com with SMTP id 5614622812f47-495b0cf250dso8538b6e.3 for ; Thu, 02 Jul 2026 17:49:29 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1783039769; x=1783644569; h=to:from:subject:message-id:date:mime-version:x-gm-message-state :from:to:cc:subject:date:message-id:reply-to; bh=72vkMoAkyO/RjRcmBneuTlcd8PRMwwf4g5+yF9K2ubE=; b=h0gvAV89YGhWkJdjUpAanefLZ3v3IuALiV+Ra2sxg/WcEHFSTdMFJjbC55Z8hy0b20 x7P3G2yxpPAeN+IyhLXmLfo3PRq669vfbQQA5tUgDJ3QUSD5kIE3+77RZXBMRj3LZzOR v2cXlwWxewB2iBW1rO9i7eZQNOK85t04gqlLYKvagN21AQndUIttuimFiDJUGszC6kf+ k0dBjTjgqEss8uKX2SN9AAXnUZEIQS7NfV559Fb0yPNDtttyJPN2zP714hYQtza0f1Rl x7n5Az2T0JbekryGydgPPjmCbxLTIH28GmUqR7aS9L5Z+64oHpV5r1gJzulVW+YmC1ck klwQ== X-Forwarded-Encrypted: i=1; AFNElJ90XclBjo1BjEKqmq3zw91R9z/ndFc+aGD7/UyQqaWlaAePO03IW2i+Bq7NOEffeLUOtzR5tTt+sv2k8/0=@vger.kernel.org X-Gm-Message-State: AOJu0Yz8KAAlV+21rj3mN3Huixi8xJMnRkLqJ/mbj5IEfXbNUXy2Q+mW Cj+y8NdbwSJMWunkxulMZruOC3+Hj06xXvU/jHx2wnK9NrU6ZcnqhXPvZb8KBSwHdbS+xGdZg8x MzVhKzKxcORA7QRAEtQ2SbLB9eRfLeBqIbMv/LWg0MWYHKubBo28BLasiV/U= Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Received: by 2002:a05:6808:2209:b0:497:da7f:179c with SMTP id 5614622812f47-497da7f2670mr2635291b6e.27.1783039769019; Thu, 02 Jul 2026 17:49:29 -0700 (PDT) Date: Thu, 02 Jul 2026 17:49:29 -0700 X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <6a470719.6912059f.e0473.0007.GAE@google.com> Subject: [syzbot] [exfat?] KCSAN: data-race in copy_folio_from_iter_atomic / fat12_ent_put (5) 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: 665159e24674 Merge tag 'probes-fixes-v7.2-rc1' of git://gi.. git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=1484b146580000 kernel config: https://syzkaller.appspot.com/x/.config?x=84b3039e8461eef5 dashboard link: https://syzkaller.appspot.com/bug?extid=e9aa2f4bc3623d1be5cf 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/31c1c90dee17/disk-665159e2.raw.xz vmlinux: https://storage.googleapis.com/syzbot-assets/d073e04a63f4/vmlinux-665159e2.xz kernel image: https://storage.googleapis.com/syzbot-assets/0421e67defd8/bzImage-665159e2.xz IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+e9aa2f4bc3623d1be5cf@syzkaller.appspotmail.com ================================================================== BUG: KCSAN: data-race in copy_folio_from_iter_atomic / fat12_ent_put write to 0xffff888121f76082 of 1 bytes by task 6014 on cpu 1: fat12_ent_put+0x74/0x180 fs/fat/fatent.c:168 fat_alloc_clusters+0x55e/0xc40 fs/fat/fatent.c:508 fat_add_cluster fs/fat/inode.c:108 [inline] __fat_get_block fs/fat/inode.c:155 [inline] fat_get_block+0x252/0x5e0 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 0xffff888121f76000 of 512 bytes by task 49 on cpu 0: memcpy_from_iter lib/iov_iter.c:85 [inline] iterate_bvec include/linux/iov_iter.h:123 [inline] iterate_and_advance2 include/linux/iov_iter.h:306 [inline] iterate_and_advance include/linux/iov_iter.h:330 [inline] __copy_from_iter lib/iov_iter.c:261 [inline] copy_folio_from_iter_atomic+0x728/0x10a0 lib/iov_iter.c:491 generic_perform_write+0x2c4/0x490 mm/filemap.c:4376 shmem_file_write_iter+0xc5/0xf0 mm/shmem.c:3414 lo_rw_aio+0x6a9/0x760 drivers/block/loop.c:-1 do_req_filebacked drivers/block/loop.c:-1 [inline] loop_handle_cmd drivers/block/loop.c:1921 [inline] loop_process_work+0x567/0xac0 drivers/block/loop.c:1956 loop_workfn+0x31/0x40 drivers/block/loop.c:1980 process_one_work kernel/workqueue.c:3322 [inline] process_scheduled_works+0x4d4/0x9a0 kernel/workqueue.c:3405 worker_thread+0x569/0x750 kernel/workqueue.c:3486 kthread+0x221/0x270 kernel/kthread.c:436 ret_from_fork+0x146/0x330 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 Reported by Kernel Concurrency Sanitizer on: CPU: 0 UID: 0 PID: 49 Comm: kworker/u8:3 Tainted: G W syzkaller #0 PREEMPT(lazy) Tainted: [W]=WARN Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026 Workqueue: loop6 loop_workfn ================================================================== --- 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