[BUG] INFO: rcu detected stall in sys_io_submit

[Guoyu Yin]

Hi,

I discovered a kernel crash using the Syzkaller framework, described
as "INFO: rcu detected stall in sys_io_submit". This issue occurs
during the execution of the sys_io_submit system call, where RCU
detects a stall on CPU 3.

>From the dmesg log, CPU 3 is stuck in the enqueue_hrtimer function
(kernel/time/hrtimer.c:1085) while handling an hrtimer interrupt.
Meanwhile, the task syz-executor.1 is stuck in memory management
functions (e.g., unmap_mapping_pages, mm/memory.c:3849) during
sys_io_submit execution. This likely causes the RCU stall.

I suspect this is due to delays in hrtimer processing or prolonged
blocking in memory management operations. I recommend reviewing the
enqueue_hrtimer implementation and the interaction between
sys_io_submit, AIO, and the EXT4 filesystem.

The full dmesg log is attached. Please feel free to contact me for
additional information or reproduction steps.

This can be reproduced on:

HEAD commit:

fac04efc5c793dccbd07e2d59af9f90b7fc0dca4

report: https://pastebin.com/raw/D6PmW878

console output : https://pastebin.com/raw/qeLqJsRF

kernel config: https://pastebin.com/raw/zrj9jd1V

C reproducer : https://pastebin.com/raw/EprKHENh

Best regards,

Guoyu