From: Steven Rostedt <rostedt@goodmis.org>
To: Masami Hiramatsu <mhiramat@kernel.org>
Cc: linux-kernel@vger.kernel.org
Subject: Re: [BUGFIX PATCH] tracing/kprobes: Fix strpbrk() argument order
Date: Fri, 2 Nov 2018 09:54:24 -0400 [thread overview]
Message-ID: <20181102095424.20c500ea@gandalf.local.home> (raw)
In-Reply-To: <20181102161459.86f0622bd01518a2eb06e1d5@kernel.org>
On Fri, 2 Nov 2018 16:14:59 +0900
Masami Hiramatsu <mhiramat@kernel.org> wrote:
> On Thu, 1 Nov 2018 15:10:14 -0400
> Steven Rostedt <rostedt@goodmis.org> wrote:
>
> > On Thu, 1 Nov 2018 23:29:28 +0900
> > Masami Hiramatsu <mhiramat@kernel.org> wrote:
> >
> > > Fix strpbrk()'s argument order, it must pass acceptable string
> > > in 2nd argument. Note that this can cause a kernel panic where
> > > it recovers backup character to code->data.
> > >
> > > Fixes: a6682814f371 ("tracing/kprobes: Allow kprobe-events to record module symbol")
> > > Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
> >
> > Thanks Masami,
> >
> > I'm pulling this and starting to test it.
>
> Thank you! I still couldn't believe how this bug passed through the tests...
I am too. I'm running tests with and without this patch, and the patch
doesn't appear to be making much difference.
Then I tested with this:
diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c
index 3ef15a6683c0..4ddafddf1343 100644
--- a/kernel/trace/trace_probe.c
+++ b/kernel/trace/trace_probe.c
@@ -516,6 +516,7 @@ void traceprobe_free_probe_arg(struct probe_arg
*arg) kfree(code->data);
code++;
}
+ printk("free arg->code %s\n", arg->code);
kfree(arg->code);
kfree(arg->name);
kfree(arg->comm);
@@ -535,11 +536,15 @@ int traceprobe_update_arg(struct probe_arg *arg)
if (code[1].op != FETCH_OP_IMM)
return -EINVAL;
+ tmp = strpbrk(code->data, "+-");
+ printk("first tmp tmp=%s\n", tmp);
tmp = strpbrk("+-", code->data);
+ printk("second tmp=%s data=%s\n", tmp,
code->data); if (tmp)
c = *tmp;
ret =
traceprobe_split_symbol_offset(code->data, &offset);
+ printk("third data=%s\n", code->data);
if (ret)
return ret;
@@ -547,6 +552,7 @@ int traceprobe_update_arg(struct probe_arg *arg)
(unsigned
long)kallsyms_lookup_name(code->data); if (tmp)
*tmp = c;
+ printk("forth data=%s\n", code->data);
if (!code[1].immediate)
return -ENOENT;
code[1].immediate += offset;
And I don't see where that code->data is used elsewhere. That is, why
even bother saving the character?
-- Steve
next prev parent reply other threads:[~2018-11-02 13:54 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-01 14:29 [BUGFIX PATCH] tracing/kprobes: Fix strpbrk() argument order Masami Hiramatsu
2018-11-01 19:10 ` Steven Rostedt
2018-11-02 7:14 ` Masami Hiramatsu
2018-11-02 13:54 ` Steven Rostedt [this message]
2018-11-03 11:54 ` Masami Hiramatsu
2018-11-03 13:17 ` Steven Rostedt
2018-11-03 16:21 ` Masami Hiramatsu
2018-11-03 16:03 ` [RFC PATCH] tracing/kprobes: Avoid parsing symbol+offset when updating arguments Masami Hiramatsu
2018-11-03 17:43 ` Steven Rostedt
2018-11-04 2:13 ` Masami Hiramatsu
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