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Message-Id: <20241001004050.972e999c644d0e45fd2a94f8@kernel.org>
Date: Tue, 1 Oct 2024 00:40:50 +0900
From: Masami Hiramatsu (Google) <mhiramat@...nel.org>
To: Mikel Rychliski <mikel@...elr.com>
Cc: Steven Rostedt <rostedt@...dmis.org>, Mathieu Desnoyers
<mathieu.desnoyers@...icios.com>, linux-kernel@...r.kernel.org,
linux-trace-kernel@...r.kernel.org
Subject: Re: [PATCH] tracing/probes: Fix MAX_TRACE_ARGS limit handling
On Sun, 29 Sep 2024 23:17:14 -0400
Mikel Rychliski <mikel@...elr.com> wrote:
> On Sunday, September 29, 2024 7:40:18 P.M. EDT Masami Hiramatsu wrote:
> > Good catch! But this silently drop the arguments after MAX_TRACE_ARGS.
> > I rather like to reject such input with an error (-E2BIG) as below.
> > (Hmm, and I also need a new ftracetest test case for this.)
> >
> > diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c
> > index 39877c80d6cb..3f6654127d8c 100644
> > --- a/kernel/trace/trace_probe.c
> > +++ b/kernel/trace/trace_probe.c
> > @@ -2194,6 +2194,9 @@ int trace_probe_create(const char *raw_command, int
> > (*createfn)(int, const char if (!argv)
> > return -ENOMEM;
> >
> > + if (argc > MAX_TRACE_ARGS + 2)
> > + return -E2BIG;
> > +
> > if (argc)
> > ret = createfn(argc, (const char **)argv);
>
> I think the logic still needs to be cleaned up in the individual probe
> implementations (either to count consistently or remove the limit enforcement
> there), otherwise you can get an oops with something like:
>
> echo "f:testprobe copy_process" arg{1..127}=\$stack "\$arg*" > out
> cat out > /sys/kernel/debug/tracing/dynamic_events
Ah, good catch. Yes, the "$arg*" problem is still there.
>
> BTF argument expansion results in >128 arguments, but we still attempt to
> process the excess unparsed ones.
OK, can you update your version to return an error from each probe?
Thank you,
--
Masami Hiramatsu (Google) <mhiramat@...nel.org>
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