Messages in this thread Patch in this message | | | From | Yang Jihong <> | Subject | [PATCH v2] perf record: Fix coredump with --overwrite and --max-size | Date | Thu, 29 Dec 2022 12:47:28 +0000 |
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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@huawei.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.
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
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