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Subject[PATCH] kmemleak: Protect the seq start/next/stop sequence by rcu_read_lock()
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Objects passed to kmemleak_seq_next() have an incremented reference
count (hence not freed) but they may point via object_list.next to
other freed objects. To avoid this, the whole start/next/stop sequence
must be protected by rcu_read_lock().

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
---

This is a fix for bug #13761 raised on bugzilla.kernel.org.

mm/kmemleak.c | 4 +---
1 files changed, 1 insertions(+), 3 deletions(-)

diff --git a/mm/kmemleak.c b/mm/kmemleak.c
index 5aabd41..4872673 100644
--- a/mm/kmemleak.c
+++ b/mm/kmemleak.c
@@ -1217,7 +1217,6 @@ static void *kmemleak_seq_start(struct seq_file *seq, loff_t *pos)
}
object = NULL;
out:
- rcu_read_unlock();
return object;
}

@@ -1233,13 +1232,11 @@ static void *kmemleak_seq_next(struct seq_file *seq, void *v, loff_t *pos)

++(*pos);

- rcu_read_lock();
list_for_each_continue_rcu(n, &object_list) {
next_obj = list_entry(n, struct kmemleak_object, object_list);
if (get_object(next_obj))
break;
}
- rcu_read_unlock();

put_object(prev_obj);
return next_obj;
@@ -1255,6 +1252,7 @@ static void kmemleak_seq_stop(struct seq_file *seq, void *v)
* kmemleak_seq_start may return ERR_PTR if the scan_mutex
* waiting was interrupted, so only release it if !IS_ERR.
*/
+ rcu_read_unlock();
mutex_unlock(&scan_mutex);
if (v)
put_object(v);


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