[moderation] [ext4?] KCSAN: data-race in generic_buffers_fsync_noflush / writeback_single_inode

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: bee0e7762ad2 Merge tag 'for-linus-iommufd' of git://git.ke..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=10bb45bae80000
kernel config: https://syzkaller.appspot.com/x/.config?x=ac34c1f29a8029df
dashboard link: https://syzkaller.appspot.com/bug?extid=f8cba7127ad9dbb224dd
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
CC: [adilger...@dilger.ca linux...@vger.kernel.org linux-...@vger.kernel.org linux-...@vger.kernel.org ty...@mit.edu]

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/233be5f65dd2/disk-bee0e776.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/94423738a289/vmlinux-bee0e776.xz
kernel image: https://storage.googleapis.com/syzbot-assets/0b977463fa9a/bzImage-bee0e776.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+f8cba7...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in generic_buffers_fsync_noflush / writeback_single_inode

write to 0xffff8881088ff880 of 8 bytes by task 12461 on cpu 0:
writeback_single_inode+0x10e/0x4a0 fs/fs-writeback.c:1743
sync_inode_metadata+0x56/0x80 fs/fs-writeback.c:2808
generic_buffers_fsync_noflush+0xe4/0x120 fs/buffer.c:613
ext4_fsync_nojournal fs/ext4/fsync.c:88 [inline]
ext4_sync_file+0x206/0x6c0 fs/ext4/fsync.c:151
vfs_fsync_range+0x111/0x120 fs/sync.c:188
generic_write_sync include/linux/fs.h:2653 [inline]
ext4_buffered_write_iter+0x334/0x370 fs/ext4/file.c:305
ext4_file_write_iter+0x297/0xe10
do_iter_write+0x4ad/0x770 fs/read_write.c:860
vfs_iter_write+0x56/0x70 fs/read_write.c:901
iter_file_splice_write+0x462/0x7e0 fs/splice.c:736
do_splice_from fs/splice.c:933 [inline]
direct_splice_actor+0x8a/0xb0 fs/splice.c:1142
splice_direct_to_actor+0x31d/0x690 fs/splice.c:1088
do_splice_direct+0x10d/0x190 fs/splice.c:1194
do_sendfile+0x3c4/0x980 fs/read_write.c:1254
__do_sys_sendfile64 fs/read_write.c:1322 [inline]
__se_sys_sendfile64 fs/read_write.c:1308 [inline]
__x64_sys_sendfile64+0x110/0x150 fs/read_write.c:1308
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x44/0x110 arch/x86/entry/common.c:82
entry_SYSCALL_64_after_hwframe+0x63/0x6b

read to 0xffff8881088ff880 of 8 bytes by task 12477 on cpu 1:
generic_buffers_fsync_noflush+0x89/0x120 fs/buffer.c:608
ext4_fsync_nojournal fs/ext4/fsync.c:88 [inline]
ext4_sync_file+0x206/0x6c0 fs/ext4/fsync.c:151
vfs_fsync_range+0x111/0x120 fs/sync.c:188
generic_write_sync include/linux/fs.h:2653 [inline]
ext4_buffered_write_iter+0x334/0x370 fs/ext4/file.c:305
ext4_file_write_iter+0x297/0xe10
do_iter_write+0x4ad/0x770 fs/read_write.c:860
vfs_iter_write+0x56/0x70 fs/read_write.c:901
iter_file_splice_write+0x462/0x7e0 fs/splice.c:736
do_splice_from fs/splice.c:933 [inline]
direct_splice_actor+0x8a/0xb0 fs/splice.c:1142
splice_direct_to_actor+0x31d/0x690 fs/splice.c:1088
do_splice_direct+0x10d/0x190 fs/splice.c:1194
do_sendfile+0x3c4/0x980 fs/read_write.c:1254
__do_sys_sendfile64 fs/read_write.c:1322 [inline]
__se_sys_sendfile64 fs/read_write.c:1308 [inline]
__x64_sys_sendfile64+0x110/0x150 fs/read_write.c:1308
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x44/0x110 arch/x86/entry/common.c:82
entry_SYSCALL_64_after_hwframe+0x63/0x6b

value changed: 0x0000000000000004 -> 0x0000000000000080

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 12477 Comm: syz-executor.1 Tainted: G W 6.7.0-rc4-syzkaller-00009-gbee0e7762ad2 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/10/2023
==================================================================


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.