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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: Török Edwin <edwintorok@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Török Edwin 2008-11-23 12:39:07 +02:00 committed by Ingo Molnar
parent 8d7c6a9616
commit cffa10aecb
1 changed files with 6 additions and 3 deletions
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9
kernel/trace/trace.c
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@ -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++) {