2022-06-10 15:41:24

by Chuang Wang

Subject: [PATCH v2] kprobes: Rollback kprobe flags on failed arm_kprobe

From: Chuang Wang <[email protected]>

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

Fixes: 12310e343755 ("kprobes: Propagate error from arm_kprobe_ftrace()")
Signed-off-by: Chuang Wang <[email protected]>
Cc: <[email protected]>
Signed-off-by: Jingren Zhou <[email protected]>
---
v1->v2:
- Supplement commit information: fixline, Cc stable

kernel/kprobes.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index f214f8c088ed..c11c79e05a4c 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -2422,8 +2422,11 @@ 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;
+ if (p != kp)
+ kp->flags |= KPROBE_FLAG_DISABLED;
+ }
}
out:
mutex_unlock(&kprobe_mutex);
--
2.34.1

2022-06-12 15:10:08

by Masami Hiramatsu

Subject: Re: [PATCH v2] kprobes: Rollback kprobe flags on failed arm_kprobe

On Fri, 10 Jun 2022 23:09:33 +0800
Chuang <[email protected]> wrote:

> From: Chuang Wang <[email protected]>
>
> 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
>

This looks good to me.

Acked-by: Masami Hiramatsu (Google) <[email protected]>

Thanks for update!

> Fixes: 12310e343755 ("kprobes: Propagate error from arm_kprobe_ftrace()")
> Signed-off-by: Chuang Wang <[email protected]>
> Cc: <[email protected]>
> Signed-off-by: Jingren Zhou <[email protected]>
> ---
> v1->v2:
> - Supplement commit information: fixline, Cc stable
>
> kernel/kprobes.c | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/kprobes.c b/kernel/kprobes.c
> index f214f8c088ed..c11c79e05a4c 100644
> --- a/kernel/kprobes.c
> +++ b/kernel/kprobes.c
> @@ -2422,8 +2422,11 @@ 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;
> + if (p != kp)
> + kp->flags |= KPROBE_FLAG_DISABLED;
> + }
> }
> out:
> mutex_unlock(&kprobe_mutex);
> --
> 2.34.1
>


--
Masami Hiramatsu (Google) <[email protected]>