On Fri, 2 Nov 2018 09:54:24 -0400
Steven Rostedt <rost...@goodmis.org> wrote:
> On Fri, 2 Nov 2018 16:14:59 +0900
> Masami Hiramatsu <mhira...@kernel.org> wrote:
>
> > On Thu, 1 Nov 2018 15:10:14 -0400
> > Steven Rostedt <rost...@goodmis.org> wrote:
> >
> > > On Thu, 1 Nov 2018 23:29:28 +0900
> > > Masami Hiramatsu <mhira...@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 <mhira...@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.
Maybe traceprobe_free_probe_arg() is silently failed.
>
> 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?
Would you mean parsing the symbol+offs every time is useless?
It needs to solve the symbol address always because traceprobe_update_arg
is called when new symbols added on the kernel (by loading modules).
Hmm, maybe I can introduce a struct like
struct symbol_offset {
long offset;
char symbol[];
};
and use it instead of parsing the symbol+offset always.
Thanks,
--
Masami Hiramatsu <mhira...@kernel.org>
