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Message-ID: <Z-RFu_PLmKMq8YFU@google.com>
Date: Wed, 26 Mar 2025 11:21:47 -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 v1] perf trace: Fix possible insufficient allocation of
argument formats
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.
Thanks for the fix. I've noticed this too but I feel like we can make
syscall__alloc_arg_fmts() a bit simpler.
How about this?
Thanks,
Namhyung
---8<---
diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c
index 6ac51925ea4249c2..b9bdab52f5801c3a 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");
--
2.49.0.395.g12beb8f557-goog
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