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SubjectRe: [PATCH] kprobes: Rollback kprobe flags on failed arm_kprobe
Hi Chuang,

On Thu, 2 Jun 2022 15:32:59 +0800
Chuang <nashuiliang@gmail.com> wrote:

> From: Chuang Wang <nashuiliang@gmail.com>
>
> In aggrprobe scenes, if arm_kprobe() returns an error(e.g. livepatch and
> kprobe are using the same function X), kprobe flags, while has been
> modified to ~KPROBE_FLAG_DISABLED, is not rollled back.
>
> Then, __disable_kprobe() will be failed in __unregister_kprobe_top(),
> the kprobe list will be not removed from aggrprobe, memory leaks or
> illegal pointers will be caused.
>
> WARN disarm_kprobe:
> Failed to disarm kprobe-ftrace at 00000000c729fdbc (-2)
> RIP: 0010:disarm_kprobe+0xcc/0x110
> Call Trace:
> __disable_kprobe+0x78/0x90
> __unregister_kprobe_top+0x13/0x1b0
> ? _cond_resched+0x15/0x30
> unregister_kprobes+0x32/0x80
> unregister_kprobe+0x1a/0x20
>
> Illegal Pointers:
> BUG: unable to handle kernel paging request at 0000000000656369
> RIP: 0010:__get_valid_kprobe+0x69/0x90
> Call Trace:
> register_kprobe+0x30/0x60
> __register_trace_kprobe.part.7+0x8b/0xc0
> create_local_trace_kprobe+0xd2/0x130
> perf_kprobe_init+0x83/0xd0

Oops, thanks for reporting!

> Signed-off-by: Chuang Wang <nashuiliang@gmail.com>
> Signed-off-by: Jingren Zhou <zhoujingren@didiglobal.com>

This should go to stable, so add below tag. (No need to CC to stable)

Fixes: 12310e343755 ("kprobes: Propagate error from arm_kprobe_ftrace()")
Cc: stable@vger.kernel.org

And could you also update this patch as below?

> ---
> kernel/kprobes.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/kprobes.c b/kernel/kprobes.c
> index f214f8c088ed..96c75e23113c 100644
> --- a/kernel/kprobes.c
> +++ b/kernel/kprobes.c
> @@ -2422,8 +2422,10 @@ int enable_kprobe(struct kprobe *kp)
> if (!kprobes_all_disarmed && kprobe_disabled(p)) {
> p->flags &= ~KPROBE_FLAG_DISABLED;
> ret = arm_kprobe(p);
> - if (ret)
> + if (ret) {
> p->flags |= KPROBE_FLAG_DISABLED;

Here, can you add a check?

if (p != kp)

> + kp->flags |= KPROBE_FLAG_DISABLED;

Thus is is clear that this is corresponding to
---
if (p != kp)
kp->flags &= ~KPROBE_FLAG_DISABLED;
---

Thank you,

> + }
> }
> out:
> mutex_unlock(&kprobe_mutex);
> --
> 2.34.1
>


--
Masami Hiramatsu (Google) <mhiramat@kernel.org>

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