ext4: fix timer use-after-free on failed mount

Syzbot has found an ODEBUG bug in ext4_fill_super

The del_timer_sync function cancels the s_err_report timer,
which reminds about filesystem errors daily. We should
guarantee the timer is no longer active before kfree(sbi).

When filesystem mounting fails, the flow goes to failed_mount3,
where an error occurs when ext4_stop_mmpd is called, causing
a read I/O failure. This triggers the ext4_handle_error function
that ultimately re-arms the timer,
leaving the s_err_report timer active before kfree(sbi) is called.

Fix the issue by canceling the s_err_report timer after calling ext4_stop_mmpd.

Signed-off-by: Xiaxi Shen <[email protected]>
Reported-and-tested-by: [email protected]
Closes: https://syzkaller.appspot.com/bug?extid=59e0101c430934bc9a36
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Theodore Ts'o <[email protected]>
Cc: [email protected]

0 files changed, 0 insertions, 0 deletions