[moderation] [ext4?] KCSAN: data-race in generic_buffers_fsync_noflush / inode_cgwb_move_to_attached (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 2d5404caa8c7 Linux 6.12-rc7
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=139bfea7980000
kernel config: https://syzkaller.appspot.com/x/.config?x=29fedde79f609854
dashboard link: https://syzkaller.appspot.com/bug?extid=10f039cf2ae179d227c5
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/15a7713979b8/disk-2d5404ca.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/b51c4f695d4a/vmlinux-2d5404ca.xz
kernel image: https://storage.googleapis.com/syzbot-assets/e8c0f17bc00b/bzImage-2d5404ca.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+10f039...@syzkaller.appspotmail.com

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

write to 0xffff888106ac2138 of 4 bytes by task 4291 on cpu 1:
inode_cgwb_move_to_attached+0x9a/0x300 fs/fs-writeback.c:310
writeback_single_inode+0x2b5/0x3f0 fs/fs-writeback.c:1796
sync_inode_metadata+0x5c/0x90 fs/fs-writeback.c:2849
generic_buffers_fsync_noflush+0xd8/0x120 fs/buffer.c:610
ext4_fsync_nojournal fs/ext4/fsync.c:88 [inline]
ext4_sync_file+0x1ff/0x6c0 fs/ext4/fsync.c:151
vfs_fsync_range+0x116/0x130 fs/sync.c:188
generic_write_sync include/linux/fs.h:2871 [inline]
ext4_buffered_write_iter+0x326/0x370 fs/ext4/file.c:305
ext4_file_write_iter+0x293/0xe10
iter_file_splice_write+0x5f1/0x980 fs/splice.c:743
do_splice_from fs/splice.c:941 [inline]
direct_splice_actor+0x160/0x2c0 fs/splice.c:1164
splice_direct_to_actor+0x302/0x670 fs/splice.c:1108
do_splice_direct_actor fs/splice.c:1207 [inline]
do_splice_direct+0xd7/0x150 fs/splice.c:1233
do_sendfile+0x39b/0x970 fs/read_write.c:1388
__do_sys_sendfile64 fs/read_write.c:1455 [inline]
__se_sys_sendfile64 fs/read_write.c:1441 [inline]
__x64_sys_sendfile64+0x110/0x150 fs/read_write.c:1441
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 0xffff888106ac2138 of 4 bytes by task 4288 on cpu 0:
generic_buffers_fsync_noflush+0x83/0x120 fs/buffer.c:605
ext4_fsync_nojournal fs/ext4/fsync.c:88 [inline]
ext4_sync_file+0x1ff/0x6c0 fs/ext4/fsync.c:151
vfs_fsync_range+0x116/0x130 fs/sync.c:188
generic_write_sync include/linux/fs.h:2871 [inline]
ext4_buffered_write_iter+0x326/0x370 fs/ext4/file.c:305
ext4_file_write_iter+0x293/0xe10
iter_file_splice_write+0x5f1/0x980 fs/splice.c:743
do_splice_from fs/splice.c:941 [inline]
direct_splice_actor+0x160/0x2c0 fs/splice.c:1164
splice_direct_to_actor+0x302/0x670 fs/splice.c:1108
do_splice_direct_actor fs/splice.c:1207 [inline]
do_splice_direct+0xd7/0x150 fs/splice.c:1233
do_sendfile+0x39b/0x970 fs/read_write.c:1388
__do_sys_sendfile64 fs/read_write.c:1455 [inline]
__se_sys_sendfile64 fs/read_write.c:1441 [inline]
__x64_sys_sendfile64+0x110/0x150 fs/read_write.c:1441
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: 0x00000002 -> 0x00000020

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 4288 Comm: syz.4.210 Not tainted 6.12.0-rc7-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
==================================================================


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[syzbot]

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