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SubjectRe: [PATCH] kprobes: avoid the kprobe being re-registered
On 2017/10/26 22:39, Masami Hiramatsu wrote:
> On Thu, 26 Oct 2017 20:11:25 +0800
> Zhou Chengming<zhouchengming1@huawei.com> wrote:
>
>> Old code use check_kprobe_rereg() to check if the kprobe has been
>> registered already, but check_kprobe_rereg() will release the
>> kprobe_mutex then, so maybe two paths will pass the check and
>> register the same kprobe. This patch put the check inside the mutex.
> Still no good, see below comment.
>
>> Signed-off-by: Zhou Chengming<zhouchengming1@huawei.com>
>> ---
>> kernel/kprobes.c | 23 ++++++-----------------
>> 1 file changed, 6 insertions(+), 17 deletions(-)
>>
>> diff --git a/kernel/kprobes.c b/kernel/kprobes.c
>> index a1606a4..2a4873a 100644
>> --- a/kernel/kprobes.c
>> +++ b/kernel/kprobes.c
>> @@ -1443,19 +1443,6 @@ static struct kprobe *__get_valid_kprobe(struct kprobe *p)
>> return ap;
>> }
>>
>> -/* Return error if the kprobe is being re-registered */
>> -static inline int check_kprobe_rereg(struct kprobe *p)
>> -{
>> - int ret = 0;
>> -
>> - mutex_lock(&kprobe_mutex);
>> - if (__get_valid_kprobe(p))
>> - ret = -EINVAL;
>> - mutex_unlock(&kprobe_mutex);
>> -
>> - return ret;
>> -}
>> -
>> int __weak arch_check_ftrace_location(struct kprobe *p)
>> {
>> unsigned long ftrace_addr;
>> @@ -1536,10 +1523,6 @@ int register_kprobe(struct kprobe *p)
>> return PTR_ERR(addr);
>> p->addr = addr;
>>
>> - ret = check_kprobe_rereg(p);
>> - if (ret)
>> - return ret;
>> -
>> /* User can pass only KPROBE_FLAG_DISABLED to register_kprobe */
>> p->flags&= KPROBE_FLAG_DISABLED;
>> p->nmissed = 0;
> here, we already modifies the kprobe. We need to check and reject before modifying it.
>
> Thank you,

Ah, right. We should put the modifies after the re-reg check. I will send a patch-v2.

Thank you.

>> @@ -1551,6 +1534,12 @@ int register_kprobe(struct kprobe *p)
>>
>> mutex_lock(&kprobe_mutex);
>>
>> + /* Return error if the kprobe is being re-registered */
>> + if (__get_valid_kprobe(p)) {
>> + ret = -EINVAL;
>> + goto out;
>> + }
>> +
>> old_p = get_kprobe(p->addr);
>> if (old_p) {
>> /* Since this may unoptimize old_p, locking text_mutex. */
>> --
>> 1.8.3.1
>>
>


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