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

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 6a0e38264012 Merge tag 'for-6.11-rc2-tag' of git://git.ker..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=17b7f061980000
kernel config: https://syzkaller.appspot.com/x/.config?x=cb57e6ebf675f9d2
dashboard link: https://syzkaller.appspot.com/bug?extid=df649ff02864b5d5fe27
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 ty...@mit.edu]

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/753a842a966b/disk-6a0e3826.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/e12e23519777/vmlinux-6a0e3826.xz
kernel image: https://storage.googleapis.com/syzbot-assets/bce0584a8cb4/bzImage-6a0e3826.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+df649f...@syzkaller.appspotmail.com

[EXT4 FS bs=1024, gc=1, bpg=131072, ipg=32, mo=e855c01c, mo2=0003]
System zones: 0-1, 3-36
EXT4-fs (loop0): mounted filesystem 00000000-0000-0000-0000-000000000000 r/w without journal. Quota mode: writeback.
==================================================================
BUG: KCSAN: data-race in generic_buffers_fsync_noflush / redirty_tail_locked

read-write to 0xffff888113850ac8 of 8 bytes by task 3733 on cpu 0:
redirty_tail_locked+0x56/0x270 fs/fs-writeback.c:1346
writeback_single_inode+0x1ea/0x4a0 fs/fs-writeback.c:1792
sync_inode_metadata+0x5c/0x90 fs/fs-writeback.c:2842
generic_buffers_fsync_noflush+0xe4/0x130 fs/buffer.c:610
ext4_fsync_nojournal fs/ext4/fsync.c:88 [inline]
ext4_sync_file+0x20b/0x6c0 fs/ext4/fsync.c:151
vfs_fsync_range+0x122/0x140 fs/sync.c:188
generic_write_sync include/linux/fs.h:2816 [inline]
ext4_buffered_write_iter+0x338/0x380 fs/ext4/file.c:305
ext4_file_write_iter+0x29f/0xe30
iter_file_splice_write+0x5e6/0x970 fs/splice.c:743
do_splice_from fs/splice.c:941 [inline]
direct_splice_actor+0x16c/0x2c0 fs/splice.c:1164
splice_direct_to_actor+0x305/0x670 fs/splice.c:1108
do_splice_direct_actor fs/splice.c:1207 [inline]
do_splice_direct+0xd7/0x150 fs/splice.c:1233
do_sendfile+0x3ab/0x950 fs/read_write.c:1295
__do_sys_sendfile64 fs/read_write.c:1362 [inline]
__se_sys_sendfile64 fs/read_write.c:1348 [inline]
__x64_sys_sendfile64+0x110/0x150 fs/read_write.c:1348
x64_sys_call+0xed5/0x2d60 arch/x86/include/generated/asm/syscalls_64.h:41
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff888113850ac8 of 8 bytes by task 3727 on cpu 1:
generic_buffers_fsync_noflush+0x89/0x130 fs/buffer.c:605
ext4_fsync_nojournal fs/ext4/fsync.c:88 [inline]
ext4_sync_file+0x20b/0x6c0 fs/ext4/fsync.c:151
vfs_fsync_range+0x122/0x140 fs/sync.c:188
generic_write_sync include/linux/fs.h:2816 [inline]
ext4_buffered_write_iter+0x338/0x380 fs/ext4/file.c:305
ext4_file_write_iter+0x29f/0xe30
iter_file_splice_write+0x5e6/0x970 fs/splice.c:743
do_splice_from fs/splice.c:941 [inline]
direct_splice_actor+0x16c/0x2c0 fs/splice.c:1164
splice_direct_to_actor+0x305/0x670 fs/splice.c:1108
do_splice_direct_actor fs/splice.c:1207 [inline]
do_splice_direct+0xd7/0x150 fs/splice.c:1233
do_sendfile+0x3ab/0x950 fs/read_write.c:1295
__do_sys_sendfile64 fs/read_write.c:1362 [inline]
__se_sys_sendfile64 fs/read_write.c:1348 [inline]
__x64_sys_sendfile64+0x110/0x150 fs/read_write.c:1348
x64_sys_call+0xed5/0x2d60 arch/x86/include/generated/asm/syscalls_64.h:41
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x0000000000000087 -> 0x0000000000000080

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 3727 Comm: syz.0.95 Not tainted 6.11.0-rc2-syzkaller-00027-g6a0e38264012 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/27/2024
==================================================================


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[syzbot]

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