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SubjectRe: [BUGFIX] kprobes: prevent re-registration of the same kprobe - take2
On Mon, Sep 14, 2009 at 12:25:41PM -0400, Masami Hiramatsu wrote:
> Ananth N Mavinakayanahalli wrote:
>> On Sun, Sep 13, 2009 at 09:47:39PM -0400, Masami Hiramatsu wrote:
>>> Ananth N Mavinakayanahalli wrote:
>>>> On Fri, Sep 11, 2009 at 05:12:54AM +0200, Frederic Weisbecker wrote:
>>>>> On Thu, Sep 10, 2009 at 07:53:30PM -0400, Masami Hiramatsu wrote:

...

>> +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 == p)
>
> Here, since __get_valid_kprobe(p) will return aggr_kprobe of 'p',
> you just need to check old_p != NULL.

Right!

---
Prevent re-registration of the same kprobe. This situation, though
unlikely, needs to be flagged since it can lead to a system crash if its
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>
---
kernel/kprobes.c | 58 ++++++++++++++++++++++++++++++++++++-------------------
1 file changed, 38 insertions(+), 20 deletions(-)

Index: linux-2.6.31/kernel/kprobes.c
===================================================================
--- linux-2.6.31.orig/kernel/kprobes.c
+++ linux-2.6.31/kernel/kprobes.c
@@ -681,6 +681,40 @@ static kprobe_opcode_t __kprobes *kprobe
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;
@@ -693,6 +727,10 @@ int __kprobes register_kprobe(struct kpr
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)) {
@@ -762,26 +800,6 @@ 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.
*/

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