kprobes: Prevent re-registration of the same kprobe

Prevent re-registration of the same kprobe. This situation, though
unlikely, needs to be flagged since it can lead to a system crash if
it's not handled.

The core change itself is small, but the helper routine needed to be
moved around a bit; hence the diffstat.

Signed-off-by: Ananth N Mavinakayanahalli<ananth@in.ibm.com>
Acked-by: Masami Hiramatsu <mhiramat@redhat.com>
Cc: Jim Keniston <jkenisto@us.ibm.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Frank Ch. Eigler <fche@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Jason Baron <jbaron@redhat.com>
Cc: K.Prasad <prasad@linux.vnet.ibm.com>
Cc: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Tom Zanussi <tzanussi@gmail.com>
LKML-Reference: <20090915051307.GB26458@in.ibm.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>

diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 00d01b0..b946761 100644 (file)
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -676,6 +676,40 @@ static kprobe_opcode_t __kprobes *kprobe_addr(struct kprobe *p)
        return (kprobe_opcode_t *)(((char *)addr) + p->offset);
 }
 
+/* Check passed kprobe is valid and return kprobe in kprobe_table. */
+static struct kprobe * __kprobes __get_valid_kprobe(struct kprobe *p)
+{
+       struct kprobe *old_p, *list_p;
+
+       old_p = get_kprobe(p->addr);
+       if (unlikely(!old_p))
+               return NULL;
+
+       if (p != old_p) {
+               list_for_each_entry_rcu(list_p, &old_p->list, list)
+                       if (list_p == p)
+                       /* kprobe p is a valid probe */
+                               goto valid;
+               return NULL;
+       }
+valid:
+       return old_p;
+}
+
+/* Return error if the kprobe is being re-registered */
+static inline int check_kprobe_rereg(struct kprobe *p)
+{
+       int ret = 0;
+       struct kprobe *old_p;
+
+       mutex_lock(&kprobe_mutex);
+       old_p = __get_valid_kprobe(p);
+       if (old_p)
+               ret = -EINVAL;
+       mutex_unlock(&kprobe_mutex);
+       return ret;
+}
+
 int __kprobes register_kprobe(struct kprobe *p)
 {
        int ret = 0;
@@ -688,6 +722,10 @@ int __kprobes register_kprobe(struct kprobe *p)
                return -EINVAL;
        p->addr = addr;
 
+       ret = check_kprobe_rereg(p);
+       if (ret)
+               return ret;
+
        preempt_disable();
        if (!kernel_text_address((unsigned long) p->addr) ||
            in_kprobes_functions((unsigned long) p->addr)) {
@@ -757,26 +795,6 @@ out:
 }
 EXPORT_SYMBOL_GPL(register_kprobe);
 
-/* Check passed kprobe is valid and return kprobe in kprobe_table. */
-static struct kprobe * __kprobes __get_valid_kprobe(struct kprobe *p)
-{
-       struct kprobe *old_p, *list_p;
-
-       old_p = get_kprobe(p->addr);
-       if (unlikely(!old_p))
-               return NULL;
-
-       if (p != old_p) {
-               list_for_each_entry_rcu(list_p, &old_p->list, list)
-                       if (list_p == p)
-                       /* kprobe p is a valid probe */
-                               goto valid;
-               return NULL;
-       }
-valid:
-       return old_p;
-}
-
 /*
  * Unregister a kprobe without a scheduler synchronization.
  */