From cffa10aecb6891f090a4d53a075bc40c082c45fc Mon Sep 17 00:00:00 2001
From: =?utf8?q?T=C3=B6r=C3=B6k=20Edwin?= <edwintorok@gmail.com>
Date: Sun, 23 Nov 2008 12:39:07 +0200
Subject: [PATCH] tracing/stack-tracer: fix locking and refcounts
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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>
---
kernel/trace/trace.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index dedf35f369719..4c3bd82cec49c 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -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++) {
--
2.30.2