Re: [BUG REPORT] kernel BUG in ext4_write_inline_data_end or ext4_writepages

[yebin (H)]

On 2022/12/5 16:54, Jun Nie wrote:
> Hi,
> syzbot find a new bug[1] in ext4 that's similar with bug[0], that
> leads to reboot.
> While the bug[0] can be fixed with patch[2] from Bin. This new bug is still
> triggered with the patch[2], and log[3] is collected. Both log[1] and
> log[3] are
> collected when testing bug[4] on the mainline.
>
> [0] https://syzkaller.appspot.com/bug?id=5bafe4554067100b70f58a81268aa06ea3f9c345
> [1] https://syzkaller.appspot.com/text?tag=CrashLog&x=16325fc3880000
> [2] https://lore.kernel.org/lkml/CABymUCN+NSzkunRqFs8LgqjT6vXz-gyyZYn0hQWf8V9kmcO0Hw@xxxxxxxxxxxxxx/T/
> [3] https://syzkaller.appspot.com/text?tag=CrashLog&x=155abe7b880000
> [4] https://syzkaller.appspot.com/bug?id=899b37f20ce4072bcdfecfe1647b39602e956e36
>
>
> [   38.932317][  T494] Call Trace:
> [   38.935437][  T494]  <TASK>
> [   38.938393][  T494]  ext4_write_inline_data_end+0xa39/0xdf0
> [   38.943946][  T494]  ? put_page+0xa0/0xa0
> [   38.947936][  T494]  ? ext4_da_write_begin+0x6f0/0x8d0
> [   38.953055][  T494]  ? pipe_zero+0x240/0x240
> [   38.957308][  T494]  ext4_da_write_end+0x1e2/0x950
> [   38.962082][  T494]  ? ext4_da_write_begin+0x8d0/0x8d0
> [   38.967204][  T494]  generic_perform_write+0x401/0x5f0
> [   38.972326][  T494]  ? generic_file_direct_write+0x6c0/0x6c0
> [   38.977994][  T494]  ? generic_write_checks_count+0x4b0/0x4b0
> [   38.983694][  T494]  ext4_buffered_write_iter+0x35f/0x640
> [   38.989074][  T494]  ext4_file_write_iter+0x198/0x1cd0
> [   38.994194][  T494]  ? futex_unqueue+0x156/0x180
> [   38.998795][  T494]  ? futex_wait+0x4c5/0x5c0
> [   39.003307][  T494]  ? futex_wait_setup+0x320/0x320
> [   39.008168][  T494]  ? avc_policy_seqno+0x1b/0x70
> [   39.012862][  T494]  ? ext4_file_read_iter+0x470/0x470
> [   39.017976][  T494]  vfs_write+0x8b5/0xef0
> [   39.022056][  T494]  ? file_end_write+0x1b0/0x1b0
> [   39.026739][  T494]  ? mutex_lock+0xb6/0x130
> [   39.030994][  T494]  ? bit_wait_io_timeout+0x110/0x110
> [   39.036117][  T494]  ? __fget_files+0x2d9/0x330
> [   39.040630][  T494]  ? __fdget_pos+0x268/0x300
> [   39.045054][  T494]  ? ksys_write+0x77/0x2c0
> [   39.049307][  T494]  ksys_write+0x198/0x2c0
> [   39.053472][  T494]  ? save_fpregs_to_fpstate+0x210/0x210
> [   39.058855][  T494]  ? __ia32_sys_read+0x90/0x90
> [   39.063465][  T494]  ? __kasan_check_write+0x14/0x20
> [   39.068403][  T494]  ? switch_fpu_return+0x129/0x270
> [   39.073348][  T494]  __x64_sys_write+0x7b/0x90
> [   39.077783][  T494]  do_syscall_64+0x2f/0x50
> [   39.082030][  T494]  entry_SYSCALL_64_after_hwframe+0x63/0xcd
>
> Regards,
> Jun
> .

I analyze that the above issue should be caused by the concurrency
of inline data conversion and buffer write.
At present, I haven't thought of any good solution.