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SubjectRe: [PATCH v3 1/2] kprobes: avoid the kprobe being re-registered
On Fri, 27 Oct 2017 17:23:14 +0800
Zhou Chengming <zhouchengming1@huawei.com> wrote:

> Changes:
> - We should put the modifies of the kprobe after the re-reg check.
> - And then the address_safe check.
>
> 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.
>
> Suggested-by: Masami Hiramatsu <mhiramat@kernel.org>
> Signed-off-by: Zhou Chengming <zhouchengming1@huawei.com>

Looks good to me :)

Acked-by: Masami Hiramatsu <mhiramat@kernel.org>

Thanks!

> ---
> kernel/kprobes.c | 27 ++++++++-------------------
> 1 file changed, 8 insertions(+), 19 deletions(-)
>
> diff --git a/kernel/kprobes.c b/kernel/kprobes.c
> index a1606a4..1eeedac 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;
> @@ -1536,9 +1523,13 @@ int register_kprobe(struct kprobe *p)
> return PTR_ERR(addr);
> p->addr = addr;
>
> - ret = check_kprobe_rereg(p);
> - if (ret)
> - return ret;
> + mutex_lock(&kprobe_mutex);
> +
> + /* Return error if the kprobe is being re-registered */
> + if (__get_valid_kprobe(p)) {
> + ret = -EINVAL;
> + goto out;
> + }
>
> /* User can pass only KPROBE_FLAG_DISABLED to register_kprobe */
> p->flags &= KPROBE_FLAG_DISABLED;
> @@ -1547,9 +1538,7 @@ int register_kprobe(struct kprobe *p)
>
> ret = check_kprobe_address_safe(p, &probed_mod);
> if (ret)
> - return ret;
> -
> - mutex_lock(&kprobe_mutex);
> + goto out;
>
> old_p = get_kprobe(p->addr);
> if (old_p) {
> --
> 1.8.3.1
>


--
Masami Hiramatsu <mhiramat@kernel.org>

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