From: Masami Hiramatsu <mhiramat@kernel.org>
To: Muchun Song <songmuchun@bytedance.com>
Cc: Qiang Wang <wangqiang.wq.frank@bytedance.com>,
"Naveen N . Rao" <naveen.n.rao@linux.ibm.com>,
Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>,
David Miller <davem@davemloft.net>,
Masami Hiramatsu <mhiramat@kernel.org>,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>,
Martin KaFai Lau <kafai@fb.com>, Song Liu <songliubraving@fb.com>,
Yonghong Song <yhs@fb.com>,
John Fastabend <john.fastabend@gmail.com>,
kpsingh@kernel.org, LKML <linux-kernel@vger.kernel.org>,
Networking <netdev@vger.kernel.org>, bpf <bpf@vger.kernel.org>,
Chengming Zhou <zhouchengming@bytedance.com>,
Xiongchun duan <duanxiongchun@bytedance.com>
Subject: Re: [Phishing Risk] [PATCH] kprobe: fix kretprobe stack backtrace
Date: Mon, 28 Jun 2021 22:34:30 +0900 [thread overview]
Message-ID: <20210628223430.8f903ea25977f5568ec1df6e@kernel.org> (raw)
In-Reply-To: <CAMZfGtWPi4CuVOtmUpy2N9J_mvp+5=gSAFvqV1nmvDKP+CAvQA@mail.gmail.com>
On Fri, 25 Jun 2021 18:24:12 +0800
Muchun Song <songmuchun@bytedance.com> wrote:
> On Fri, Jun 25, 2021 at 4:49 PM Qiang Wang
> <wangqiang.wq.frank@bytedance.com> wrote:
> >
> > We found that we couldn't get the correct kernel stack from
> > kretprobe. For example:
> >
> > bpftrace -e 'kr:submit_bio {print(kstack)}'
> > Attaching 1 probe...
> >
> > kretprobe_trampoline+0
> >
> > kretprobe_trampoline+0
> >
> > The problem is caused by the wrong instruction register which
> > points to the address of kretprobe_trampoline in regs.
> > So we set the real return address in instruction register.
> > Finally, we tested and successfully fixed it.
> >
> > bpftrace -e 'kr:submit_bio {print(kstack)}'
> > Attaching 1 probe...
> >
> > ext4_mpage_readpages+475
> > read_pages+139
> > page_cache_ra_unbounded+417
> > filemap_get_pages+245
> > filemap_read+169
> > __kernel_read+327
> > bprm_execve+648
> > do_execveat_common.isra.39+409
> > __x64_sys_execve+50
> > do_syscall_64+54
> > entry_SYSCALL_64_after_hwframe+68
> >
> > Reported-by: Chengming Zhou <zhouchengming@bytedance.com>
> > Signed-off-by: Qiang Wang <wangqiang.wq.frank@bytedance.com>
>
> Seems like a bug. Maybe we should add a "Fixes" tag here.
No, that is not a bug in the kretprobes. If you carefully check
kretprobes provided the rp->addr as ip address. BPF just did not
use it.
Anyway, I already made a same patch in the below series.
https://lore.kernel.org/bpf/162400000592.506599.4695807810528866713.stgit@devnote2/
and you can see that the series is including below 3 patches for that change.
https://lore.kernel.org/bpf/162399997853.506599.13701157683968161733.stgit@devnote2/
https://lore.kernel.org/bpf/162399998747.506599.1115560529431673586.stgit@devnote2/
https://lore.kernel.org/bpf/162399999702.506599.16339931387573094059.stgit@devnote2/
Without these patches, this change will break other arch.
Thanks,
>
> > ---
> > kernel/kprobes.c | 3 +++
> > 1 file changed, 3 insertions(+)
> >
> > diff --git a/kernel/kprobes.c b/kernel/kprobes.c
> > index 745f08fdd..1130381ca 100644
> > --- a/kernel/kprobes.c
> > +++ b/kernel/kprobes.c
> > @@ -1899,6 +1899,9 @@ unsigned long __kretprobe_trampoline_handler(struct pt_regs *regs,
> > current->kretprobe_instances.first = node->next;
> > node->next = NULL;
> >
> > + /* Kretprobe handler expects address is the real return address */
> > + instruction_pointer_set(regs, (unsigned long)correct_ret_addr);
> > +
> > /* Run them.. */
> > while (first) {
> > ri = container_of(first, struct kretprobe_instance, llist);
> > --
> > 2.20.1
> >
--
Masami Hiramatsu <mhiramat@kernel.org>
prev parent reply other threads:[~2021-06-28 13:35 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20210625084748.18128-1-wangqiang.wq.frank@bytedance.com>
2021-06-25 10:24 ` [Phishing Risk] [PATCH] kprobe: fix kretprobe stack backtrace Muchun Song
2021-06-28 13:34 ` Masami Hiramatsu [this message]
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