kprobes: fix a memory leak in function pre_handler_kretprobe()

In function pre_handler_kretprobe(), the allocated kretprobe_instance
object will get leaked if the entry_handler callback returns non-zero.
This may cause all the preallocated kretprobe_instance objects exhausted.

This issue can be reproduced by changing
samples/kprobes/kretprobe_example.c to probe "mutex_unlock".  And the fix
is straightforward: just put the allocated kretprobe_instance object back
onto the free_instances list.

[[email protected]: use raw_spin_lock/unlock]
Signed-off-by: Jiang Liu <[email protected]>
Acked-by: Jim Keniston <[email protected]>
Acked-by: Ananth N Mavinakayanahalli <[email protected]>
Cc: Masami Hiramatsu <[email protected]>
Cc: Anil S Keshavamurthy <[email protected]>
Cc: "David S. Miller" <[email protected]>
Cc: <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 29f5b65bee29321bbfef40396712e1960b9a5836..9788c0ec6f4378f19cd80e873d42a0aec7171548 100644 (file)
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -1673,8 +1673,12 @@ static int __kprobes pre_handler_kretprobe(struct kprobe *p,
                ri->rp = rp;
                ri->task = current;
 
-               if (rp->entry_handler && rp->entry_handler(ri, regs))
+               if (rp->entry_handler && rp->entry_handler(ri, regs)) {
+                       raw_spin_lock_irqsave(&rp->lock, flags);
+                       hlist_add_head(&ri->hlist, &rp->free_instances);
+                       raw_spin_unlock_irqrestore(&rp->lock, flags);
                        return 0;
+               }
 
                arch_prepare_kretprobe(ri, regs);