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Message-ID: <Z-HxsV8KyeTWeskb@gmail.com>
Date: Mon, 24 Mar 2025 16:58:41 -0700
From: Howard Chu <howardchu95@...il.com>
To: acme@...nel.org
Cc: mingo@...hat.com, namhyung@...nel.org, mark.rutland@....com,
alexander.shishkin@...ux.intel.com, jolsa@...nel.org,
irogers@...gle.com, adrian.hunter@...el.com, peterz@...radead.org,
kan.liang@...ux.intel.com, linux-perf-users@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1] perf trace: Fix possible insufficient allocation of
argument formats
Hello,
Forgot to add, there should be:
Fixes: c7b87ce0dd10 ("perf trace: Fix runtime error of index out of bounds")
Thanks,
Howard
On Mon, Mar 24, 2025 at 04:52:45PM -0700, Howard Chu wrote:
> In my previous fix of runtime error(Link:
> https://lore.kernel.org/linux-perf-users/20250122025519.361873-1-howardchu95@gmail.com/),
> I made a mistake of decrementing one unconditionally, regardless of
> whether an extra 'syscall_nr' or 'nr' field was present in
> libtraceevent's tp_format. This may cause perf trace to allocate one
> fewer arg_fmt entry than needed for the accurate representation of syscall
> arguments.
>
> This patch corrects the mistake by checking the presence of'syscall_nr' or
> 'nr', and adjusting the length of arg_fmt[] accordingly.
>
> Signed-off-by: Howard Chu <howardchu95@...il.com>
> ---
> tools/perf/builtin-trace.c | 9 ++++++---
> 1 file changed, 6 insertions(+), 3 deletions(-)
>
> diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c
> index a102748bd0c9..ad6dad8e2453 100644
> --- a/tools/perf/builtin-trace.c
> +++ b/tools/perf/builtin-trace.c
> @@ -2139,6 +2139,7 @@ static int syscall__read_info(struct syscall *sc, struct trace *trace)
> char tp_name[128];
> const char *name;
> int err;
> + bool extra_nr = false;
>
> if (sc->nonexistent)
> return -EEXIST;
> @@ -2176,20 +2177,22 @@ static int syscall__read_info(struct syscall *sc, struct trace *trace)
> return err;
> }
>
> + sc->args = sc->tp_format->format.fields;
> + if (!strcmp(sc->args->name, "__syscall_nr") || !strcmp(sc->args->name, "nr"))
> + extra_nr = true;
> /*
> * The tracepoint format contains __syscall_nr field, so it's one more
> * than the actual number of syscall arguments.
> */
> - if (syscall__alloc_arg_fmts(sc, sc->tp_format->format.nr_fields - 1))
> + if (syscall__alloc_arg_fmts(sc, sc->tp_format->format.nr_fields - (extra_nr ? 1 : 0)))
> return -ENOMEM;
>
> - sc->args = sc->tp_format->format.fields;
> /*
> * We need to check and discard the first variable '__syscall_nr'
> * or 'nr' that mean the syscall number. It is needless here.
> * So drop '__syscall_nr' or 'nr' field but does not exist on older kernels.
> */
> - if (sc->args && (!strcmp(sc->args->name, "__syscall_nr") || !strcmp(sc->args->name, "nr"))) {
> + if (sc->args && extra_nr) {
> sc->args = sc->args->next;
> --sc->nr_args;
> }
> --
> 2.45.2
>
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