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Message-ID: <Y7MEWK/z19QCaNoi@kernel.org>
Date: Mon, 2 Jan 2023 13:20:40 -0300
From: Arnaldo Carvalho de Melo <acme@...nel.org>
To: Namhyung Kim <namhyung@...nel.org>,
Yang Jihong <yangjihong1@...wei.com>
Cc: peterz@...radead.org, mingo@...hat.com, mark.rutland@....com,
alexander.shishkin@...ux.intel.com, jolsa@...nel.org,
jiwei.sun@...driver.com, linux-perf-users@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] perf record: Fix coredump with --overwrite and
--max-size
Em Thu, Dec 29, 2022 at 12:47:28PM +0000, Yang Jihong escreveu:
> When --overwrite and --max-size options of perf record are used together,
> a segmentation fault occurs. The following is an example:
>
> # perf record -e sched:sched* --overwrite --max-size 1M -a -- sleep 1
> [ perf record: Woken up 1 times to write data ]
> perf: Segmentation fault
> Obtained 1 stack frames.
> [0xc4c67f]
> Segmentation fault (core dumped)
>
> backtrace of the core file is as follows:
>
> #0 0x0000000000417990 in process_locked_synthesized_event (tool=0x0, event=0x15, sample=0x1de0, machine=0xf8) at builtin-record.c:630
> #1 0x000000000057ee53 in perf_event__synthesize_threads (nr_threads_synthesize=21, mmap_data=<optimized out>, needs_mmap=<optimized out>, machine=0x17ad9b0, process=<optimized out>, tool=0x0) at util/synthetic-events.c:1950
> #2 __machine__synthesize_threads (nr_threads_synthesize=0, data_mmap=<optimized out>, needs_mmap=<optimized out>, process=<optimized out>, threads=0x8, target=0x8, tool=0x0, machine=0x17ad9b0) at util/synthetic-events.c:1936
> #3 machine__synthesize_threads (machine=0x17ad9b0, target=0x8, threads=0x8, needs_mmap=<optimized out>, data_mmap=<optimized out>, nr_threads_synthesize=0) at util/synthetic-events.c:1947
> #4 0x000000000040165d in record__synthesize (tail=<optimized out>, rec=0xbe2520 <record>) at builtin-record.c:2010
> #5 0x0000000000403989 in __cmd_record (argc=<optimized out>, argv=<optimized out>, rec=0xbe2520 <record>) at builtin-record.c:2810
> #6 0x00000000004196ba in record__init_thread_user_masks (rec=0xbe2520 <record>, cpus=0x17a65f0) at builtin-record.c:3837
> #7 record__init_thread_masks (rec=0xbe2520 <record>) at builtin-record.c:3938
> #8 cmd_record (argc=1, argv=0x7ffdd692dc60) at builtin-record.c:4241
> #9 0x00000000004b701d in pager_command_config (var=0x0, value=0x15 <error: Cannot access memory at address 0x15>, data=0x1de0) at perf.c:117
> #10 0x00000000004b732b in get_leaf_frame_caller_aarch64 (sample=0xfffffffb, thread=0x0, usr_idx=<optimized out>) at util/arm64-frame-pointer-unwind-support.c:56
> #11 0x0000000000406331 in execv_dashed_external (argv=0x7ffdd692d9e8) at perf.c:410
> #12 run_argv (argcp=<synthetic pointer>, argv=<synthetic pointer>) at perf.c:431
> #13 main (argc=<optimized out>, argv=0x7ffdd692d9e8) at perf.c:562
>
> The reason is that record__bytes_written accesses the freed memory rec->thread_data,
> The process is as follows:
> __cmd_record
> -> record__free_thread_data
> -> zfree(&rec->thread_data) // free rec->thread_data
> -> record__synthesize
> -> perf_event__synthesize_id_index
> -> process_synthesized_event
> -> record__write
> -> record__bytes_written // access rec->thread_data
>
> we only need to check the value of done first.
> Also add variable check in record__bytes_written for code hardening,
> and save bytes_written separately to reduce one calculation.
>
> Fixes: 6d57581659f7 ("perf record: Add support for limit perf output file size")
> Signed-off-by: Yang Jihong <yangjihong1@...wei.com>
> ---
>
> Changes since v1:
> - Add variable check in record__bytes_written for code hardening.
> - Save bytes_written separately to reduce one calculation.
> - Remove rec->opts.tail_synthesize check.
Namhyung, are you ok with this now?
- Arnaldo
> tools/perf/builtin-record.c | 26 +++++++++++++++++---------
> 1 file changed, 17 insertions(+), 9 deletions(-)
>
> diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
> index 29dcd454b8e2..acba9e43e519 100644
> --- a/tools/perf/builtin-record.c
> +++ b/tools/perf/builtin-record.c
> @@ -230,16 +230,29 @@ static u64 record__bytes_written(struct record *rec)
> u64 bytes_written = rec->bytes_written;
> struct record_thread *thread_data = rec->thread_data;
>
> + if (thread_data == NULL)
> + return bytes_written;
> +
> for (t = 0; t < rec->nr_threads; t++)
> bytes_written += thread_data[t].bytes_written;
>
> return bytes_written;
> }
>
> -static bool record__output_max_size_exceeded(struct record *rec)
> +static void record__check_output_max_size_exceeded(struct record *rec)
> {
> - return rec->output_max_size &&
> - (record__bytes_written(rec) >= rec->output_max_size);
> + u64 bytes_written;
> +
> + if (rec->output_max_size == 0 || done)
> + return;
> +
> + bytes_written = record__bytes_written(rec);
> + if (bytes_written >= rec->output_max_size) {
> + fprintf(stderr, "[ perf record: perf size limit reached (%" PRIu64 " KB),"
> + " stopping session ]\n", bytes_written >> 10);
> +
> + done = 1;
> + }
> }
>
> static int record__write(struct record *rec, struct mmap *map __maybe_unused,
> @@ -260,12 +273,7 @@ static int record__write(struct record *rec, struct mmap *map __maybe_unused,
> else
> rec->bytes_written += size;
>
> - if (record__output_max_size_exceeded(rec) && !done) {
> - fprintf(stderr, "[ perf record: perf size limit reached (%" PRIu64 " KB),"
> - " stopping session ]\n",
> - record__bytes_written(rec) >> 10);
> - done = 1;
> - }
> + record__check_output_max_size_exceeded(rec);
>
> if (switch_output_size(rec))
> trigger_hit(&switch_output_trigger);
> --
> 2.30.GIT
--
- Arnaldo
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