Re: [PATCH v3 2/2] kprobes: initialize probed_mod to NULL
From: Masami Hiramatsu
Date: Sat Oct 28 2017 - 04:48:06 EST
On Fri, 27 Oct 2017 17:23:15 +0800
Zhou Chengming <zhouchengming1@xxxxxxxxxx> wrote:
> When check_kprobe_address_safe() return fail, the probed_mod
> should be set to NULL, because no module refcount held. And we
> initialize probed_mod to NULL in register_kprobe() for the same reason.
>
Ok, it's a kind of hardening code but looks good to me.
Acked-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
Thank you!
> Signed-off-by: Zhou Chengming <zhouchengming1@xxxxxxxxxx>
> ---
> kernel/kprobes.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/kprobes.c b/kernel/kprobes.c
> index 1eeedac..a04588c 100644
> --- a/kernel/kprobes.c
> +++ b/kernel/kprobes.c
> @@ -1488,6 +1488,7 @@ static int check_kprobe_address_safe(struct kprobe *p,
> * its code to prohibit unexpected unloading.
> */
> if (unlikely(!try_module_get(*probed_mod))) {
> + *probed_mod = NULL;
> ret = -ENOENT;
> goto out;
> }
> @@ -1514,7 +1515,7 @@ int register_kprobe(struct kprobe *p)
> {
> int ret;
> struct kprobe *old_p;
> - struct module *probed_mod;
> + struct module *probed_mod = NULL;
> kprobe_opcode_t *addr;
>
> /* Adjust probe address from symbol */
> --
> 1.8.3.1
>
--
Masami Hiramatsu <mhiramat@xxxxxxxxxx>