Commit bbd0b031 authored by Mathieu Desnoyers's avatar Mathieu Desnoyers Committed by Borislav Petkov (AMD)
Browse files

sched/rseq: Fix concurrency ID handling of usermodehelper kthreads 



sched_mm_cid_after_execve() does not expect NULL t->mm, but it may happen
if a usermodehelper kthread fails when attempting to execute a binary.

sched_mm_cid_fork() can be issued from a usermodehelper kthread, which
has t->flags PF_KTHREAD set.

Fixes: af7f588d ("sched: Introduce per-memory-map concurrency ID")
Reported-by: default avatarkernel test robot <yujie.liu@intel.com>
Reported-by: default avatarBorislav Petkov <bp@alien8.de>
Signed-off-by: default avatarMathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: default avatarBorislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/oe-lkp/202212301353.5c959d72-yujie.liu@intel.com
parent c8997020

kernel/sched/core.c

+3 −3
Original line number Diff line number Diff line
@@ -11343,8 +11343,8 @@ 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);



	if (!mm)

		return;

	local_irq_save(flags);

	t->mm_cid = mm_cid_get(mm);

	t->mm_cid_active = 1;
@@ -11354,7 +11354,7 @@ void sched_mm_cid_after_execve(struct task_struct *t) 


void sched_mm_cid_fork(struct task_struct *t)

{

	WARN_ON_ONCE((t->flags & PF_KTHREAD) || !t->mm || t->mm_cid != -1);

	WARN_ON_ONCE(!t->mm || t->mm_cid != -1);

	t->mm_cid_active = 1;

}

#endif