Re: [PATCH] kprobes: Fix NULL pointer dereference in unregister_kretprobes()

On Thu, Aug 6, 2026 at 2:02 AM Masami Hiramatsu <[email protected]> wrote:
>
> On Wed,  5 Aug 2026 16:12:21 +0000
> Luigi Rizzo <[email protected]> wrote:
>
> > In unregister_kretprobes(), rps[i]->rph can be NULL e.g. when called
> > after kretprobe failed registration. Under !CONFIG_KRETPROBE_ON_RETHOOK,
> > the unconditional access to rps[i]->rph->rp, causes a kernel panic due
> > to NULL pointer dereference.
>
> This is not a bug, since if register_kretprobe(rp) fails, rp must NOT be
> passed to unregister_kretprobe(rp). Or, do you find any cases where
> register_kretprobe() fails, preventing proper cleanup, and requiring
> unregister_kretprobe()? If so, we have to fix that case.

Masami, you are right, the kernel tree does not call unregister_kretprobes()
on a failed registration. I was confused by the unregister_kretprobes(rps, i);
call in the cleanup in register_kretprobes(), but the failed entry i is
not unregistered).

So aside from protective coding (but where would one stop ?
null rps, null rps[i], ... ), there is no need for this patch.

thanks for the feedback
Luigi