kprobe: fix a memory leak in function pre_handler_kretprobe()

From: Jiang Liu<[email protected]>

In function pre_handler_kretprobe(), the allocated kretprobe_instance object will be leaked if the entry_handler callback returns non-zero. This may cause all the preallocated kretprobe_instance objects exhausted. This issue could be reproduced by changing samples/kprobes/kretprobe_example.c to probe "mutex_unlock". And the fix is straight forward, just put the allocated kretprobe_instance object back onto the free_instances list.

Signed-off-by Jiang Liu<[email protected]>

Cc Hien Nguyen<[email protected]>

Cc Jim Keniston<[email protected]>

Cc Prasanna S Panchamukhi<[email protected]>

---
  kprobes.c |    6 +++++-
  1 file changed, 5 insertions(+), 1 deletion(-)

kernel/kprobes.c +5 -1

@@ -1660,8 +1660,12 @@
                 ri->rp = rp;
                 ri->task = current;
 
-               if (rp->entry_handler&&  rp->entry_handler(ri, regs))
+               if (rp->entry_handler&&  rp->entry_handler(ri, regs)) {
+                       spin_lock_irqsave(&rp->lock, flags);
+                       hlist_add_head(&ri->hlist,&rp->free_instances);
+                       spin_unlock_irqrestore(&rp->lock, flags);
                         return 0;
+               }
 
                 arch_prepare_kretprobe(ri, regs);
 

From: Jiang Liu<[email protected]>

In function pre_handler_kretprobe(), the allocated kretprobe_instance object will be leaked if the entry_handler callback returns non-zero. This may cause all the preallocated kretprobe_instance objects exhausted. This issue could be reproduced by changing samples/kprobes/kretprobe_example.c to probe "mutex_unlock". And the fix is straight forward, just put the allocated kretprobe_instance object back onto the free_instances list.

Signed-off-by Jiang Liu<[email protected]>

Cc Hien Nguyen<[email protected]>

Cc Jim Keniston<[email protected]>

Cc Prasanna S Panchamukhi<[email protected]>

---
 kprobes.c |    6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)