Messages in this thread | | | Date | Sat, 3 Nov 2018 20:54:48 +0900 | From | Masami Hiramatsu <> | Subject | Re: [BUGFIX PATCH] tracing/kprobes: Fix strpbrk() argument order |
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On Fri, 2 Nov 2018 09:54:24 -0400 Steven Rostedt <rostedt@goodmis.org> wrote:
> 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.
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 <mhiramat@kernel.org>
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