From: zhouchengming <zhouchengming1@huawei.com>
To: Borislav Petkov <bp@suse.de>
Cc: <mhiramat@kernel.org>, <ananth@linux.vnet.ibm.com>,
<anil.s.keshavamurthy@intel.com>, <davem@davemloft.net>,
<hpa@zytor.com>, <tglx@linutronix.de>, <peterz@infradead.org>,
<jkosina@suse.cz>, <rostedt@goodmis.org>, <mjurczyk@google.com>,
<x86@kernel.org>, <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] kprobes, x86/alternatives: use text_mutex to protect smp_alt_modules
Date: Fri, 27 Oct 2017 21:30:24 +0800 [thread overview]
Message-ID: <59F334F0.2070900@huawei.com> (raw)
In-Reply-To: <20171027123348.GE1305@nazgul.tnic>
On 2017/10/27 20:33, Borislav Petkov wrote:
> On Fri, Oct 27, 2017 at 07:42:45PM +0800, zhouchengming wrote:
>> This is a real bug happened on one of our machines, below is the calltrace.
>> We can see the trigger is at alternatives_text_reserved+0x20/0x80, and
>> encounter a deleted (poisoned) list_head.
> Looks like some out-of-tree, old kernel thing. We don't have
> mlx4_stats_sysfs_create() upstream and looking at the boot timestamps,
> it could be that register_jprobe() is not ready yet.
Yes, it's an out-of-tree module, loaded when boot kernel. register_kprobe()
maybe not ready yet, but the bug is not caused by it obviously.
>
> Looking at the Code, though:
>
> 20: 74 59 je 0x7b
> 22: 66 0f 1f 84 00 00 00 nopw 0x0(%rax,%rax,1)
> 29: 00 00
> 2b:* 48 3b 71 20 cmp 0x20(%rcx),%rsi<-- trapping instruction
> 2f: 72 3a jb 0x6b
> 31: 48 3b 79 28 cmp 0x28(%rcx),%rdi
> 35: 77 34 ja 0x6b
>
> %rcx is 0xdead0000000000d0 and that is POISON_POINTER_DELTA + 0xd0 so
> that looks more like smp_alt_modules is not initialized yet but I could
> could very well be wrong because this is an old kernel. So trigger that
> with the upstream kernel without out of tree modules.
The smp_alt_modules is defined by LIST_HEAD, so it's initialized at start.
A deleted list_head->next = LIST_POISON1 = 0xdead000000000000 + 0x100, then
container_of() to get the struct smp_alt_module: -0x30 = 0xdead0000000000d0
Obviously, it's a deleted list_head, and I have explained clearly how it happen in
the patch comment.
Thanks.
> Thx.
>
next prev parent reply other threads:[~2017-10-27 13:32 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-10-27 9:34 [PATCH] kprobes, x86/alternatives: use text_mutex to protect smp_alt_modules Zhou Chengming
2017-10-27 11:15 ` Borislav Petkov
2017-10-27 11:42 ` zhouchengming
2017-10-27 12:33 ` Borislav Petkov
2017-10-27 13:30 ` zhouchengming [this message]
2017-10-28 8:43 ` Masami Hiramatsu
2017-10-28 9:51 ` zhouchengming
2017-10-27 14:15 ` Peter Zijlstra
2017-10-28 1:26 ` zhouchengming
2017-10-28 8:44 ` Masami Hiramatsu
2017-10-30 8:03 ` Masami Hiramatsu
2017-10-31 21:59 ` Steven Rostedt
2017-11-01 1:48 ` zhouchengming
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=59F334F0.2070900@huawei.com \
--to=zhouchengming1@huawei.com \
--cc=ananth@linux.vnet.ibm.com \
--cc=anil.s.keshavamurthy@intel.com \
--cc=bp@suse.de \
--cc=davem@davemloft.net \
--cc=hpa@zytor.com \
--cc=jkosina@suse.cz \
--cc=linux-kernel@vger.kernel.org \
--cc=mhiramat@kernel.org \
--cc=mjurczyk@google.com \
--cc=peterz@infradead.org \
--cc=rostedt@goodmis.org \
--cc=tglx@linutronix.de \
--cc=x86@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).