[PATCH] kretprobe instance recycled by parent process

When kretprobe probes the schedule() function, if the probed process exits
then schedule() will never return, so some kretprobe instances will never
be recycled.

In this patch the parent process will recycle retprobe instances of the
probed function and there will be no memory leak of kretprobe instances.

Signed-off-by: bibo mao <bibo.mao@intel.com>
Cc: Masami Hiramatsu <hiramatu@sdl.hitachi.co.jp>
Cc: Prasanna S Panchamukhi <prasanna@in.ibm.com>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

2 files changed, 13 insertions, 6 deletions

diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 1fb9f753ef60..1156eb0977d0 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -323,10 +323,10 @@ struct hlist_head __kprobes *kretprobe_inst_table_head(struct task_struct *tsk)
 }
 
 /*
- * This function is called from exit_thread or flush_thread when task tk's
- * stack is being recycled so that we can recycle any function-return probe
- * instances associated with this task. These left over instances represent
- * probed functions that have been called but will never return.
+ * This function is called from finish_task_switch when task tk becomes dead,
+ * so that we can recycle any function-return probe instances associated
+ * with this task. These left over instances represent probed functions
+ * that have been called but will never return.
  */
 void __kprobes kprobe_flush_task(struct task_struct *tk)
 {
@@ -336,7 +336,7 @@ void __kprobes kprobe_flush_task(struct task_struct *tk)
         unsigned long flags = 0;
 
         spin_lock_irqsave(&kretprobe_lock, flags);
-        head = kretprobe_inst_table_head(current);
+        head = kretprobe_inst_table_head(tk);
         hlist_for_each_entry_safe(ri, node, tmp, head, hlist) {
                 if (ri->task == tk)
                         recycle_rp_inst(ri);
diff --git a/kernel/sched.c b/kernel/sched.c
index 7ffaabd64f89..78acdefeccca 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -49,6 +49,7 @@
 #include <linux/syscalls.h>
 #include <linux/times.h>
 #include <linux/acct.h>
+#include <linux/kprobes.h>
 #include <asm/tlb.h>
 
 #include <asm/unistd.h>
@@ -1546,8 +1547,14 @@ static inline void finish_task_switch(runqueue_t *rq, task_t *prev)
         finish_lock_switch(rq, prev);
         if (mm)
                 mmdrop(mm);
-        if (unlikely(prev_task_flags & PF_DEAD))
+        if (unlikely(prev_task_flags & PF_DEAD)) {
+                /*
+                 * Remove function-return probe instances associated with this
+                 * task and put them back on the free list.
+                 */
+                kprobe_flush_task(prev);
                 put_task_struct(prev);
+        }
 }
 
 /**