On 2022-12-30 01:48, kernel test robot wrote:
Greeting,
FYI, we noticed WARNING:at_kernel/sched/core.c:#sched_mm_cid_after_execve due to commit (built with gcc-11):
[...]
[ 17.747520][ T48] bprm_execve (exec.c:?)
[ 17.748358][ T48] ? call_usermodehelper_exec_work (umh.c:?)
[ 17.749462][ T48] kernel_execve (??:?)
[ 17.750332][ T48] call_usermodehelper_exec_async (umh.c:?)
[ 17.751363][ T48] ? call_usermodehelper_exec_work (umh.c:?)
[ 17.752163][ T48] ret_from_fork (??:?)
I suspect this check:
void sched_mm_cid_after_execve(struct task_struct *t)
{
struct mm_struct *mm = t->mm;
unsigned long flags;
WARN_ON_ONCE((t->flags & PF_KTHREAD) || !t->mm);
is too strict. AFAIU the usermodehelper thread is a kernel thread, which
happens to have a non-NULL mm after execve. We want to allow
usermodehelper threads to use rseq, so I think the appropriate approach
here would be to just warn if !t->mm:
WARN_ON_ONCE(!t->mm);
We should probably apply a similar change to the warning in
sched_mm_cid_fork() as well.
Thoughts ?
Thanks,
Mathieu
--
Mathieu Desnoyers
EfficiOS Inc.
https://www.efficios.com
