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Message-ID: <Z-T7VohMjkNolhCi@z2>
Date: Thu, 27 Mar 2025 00:16:38 -0700
From: Namhyung Kim <namhyung@...nel.org>
To: Howard Chu <howardchu95@...il.com>
Cc: acme@...nel.org, mingo@...hat.com, 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 v2] perf trace: Fix possible insufficient allocation of
argument formats
Hello,
On Wed, Mar 26, 2025 at 01:05:40PM -0700, Howard Chu wrote:
> Changes in v2:
> * Simplify the code (written by Namhyung)
Please move this below "---" after S-o-b tags so that it can be ignored
when applying.
>
> 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>
> Suggested-by: Namhyung Kim <namhyung@...nel.org>
Also please add the Fixes tag.
Thanks,
Namhyung
> ---
> tools/perf/builtin-trace.c | 16 +++++-----------
> 1 file changed, 5 insertions(+), 11 deletions(-)
>
> diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c
> index a102748bd0c9..439e152186da 100644
> --- a/tools/perf/builtin-trace.c
> +++ b/tools/perf/builtin-trace.c
> @@ -2022,9 +2022,6 @@ static int syscall__alloc_arg_fmts(struct syscall *sc, int nr_args)
> {
> int idx;
>
> - if (nr_args == RAW_SYSCALL_ARGS_NUM && sc->fmt && sc->fmt->nr_args != 0)
> - nr_args = sc->fmt->nr_args;
> -
> sc->arg_fmt = calloc(nr_args, sizeof(*sc->arg_fmt));
> if (sc->arg_fmt == NULL)
> return -1;
> @@ -2034,7 +2031,6 @@ static int syscall__alloc_arg_fmts(struct syscall *sc, int nr_args)
> sc->arg_fmt[idx] = sc->fmt->arg[idx];
> }
>
> - sc->nr_args = nr_args;
> return 0;
> }
>
> @@ -2176,14 +2172,9 @@ static int syscall__read_info(struct syscall *sc, struct trace *trace)
> return err;
> }
>
> - /*
> - * 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))
> - return -ENOMEM;
> -
> sc->args = sc->tp_format->format.fields;
> + sc->nr_args = sc->tp_format->format.nr_fields;
> +
> /*
> * We need to check and discard the first variable '__syscall_nr'
> * or 'nr' that mean the syscall number. It is needless here.
> @@ -2194,6 +2185,9 @@ static int syscall__read_info(struct syscall *sc, struct trace *trace)
> --sc->nr_args;
> }
>
> + if (syscall__alloc_arg_fmts(sc, sc->nr_args))
> + return -ENOMEM;
> +
> sc->is_exit = !strcmp(name, "exit_group") || !strcmp(name, "exit");
> sc->is_open = !strcmp(name, "open") || !strcmp(name, "openat");
>
> --
> 2.45.2
>
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