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Commit cffa10ae authored by Török Edwin's avatar Török Edwin Committed by Ingo Molnar
Browse files

tracing/stack-tracer: fix locking and refcounts 



Impact: fix refcounting/object-access bug

Hold mmap_sem while looking up/accessing vma.
Hold the RCU lock while using the task we looked up.

Signed-off-by: default avatarTörök Edwin <edwintorok@gmail.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 8d7c6a96

kernel/trace/trace.c

+6 −3
Original line number Diff line number Diff line
@@ -1462,11 +1462,15 @@ static inline int seq_print_user_ip(struct trace_seq *s, struct mm_struct *mm, 
	int ret = 1;



	if (mm) {

		const struct vm_area_struct *vma = find_vma(mm, ip);

		const struct vm_area_struct *vma;



		down_read(&mm->mmap_sem);

		vma = find_vma(mm, ip);

		if (vma) {

			file = vma->vm_file;

			vmstart = vma->vm_start;

		}

		up_read(&mm->mmap_sem);

	}

	if (file) {

		ret = trace_seq_path(s, &file->f_path);
@@ -1494,10 +1498,9 @@ seq_print_userip_objs(const struct userstack_entry *entry, struct trace_seq *s, 
		 */

		rcu_read_lock();

		task = find_task_by_vpid(entry->ent.tgid);

		rcu_read_unlock();



		if (task)

			mm = get_task_mm(task);

		rcu_read_unlock();

	}



	for (i = 0; i < FTRACE_STACK_ENTRIES; i++) {