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Subject[PATCH v2] perf ordered_events: fix crash in free_dup_event()
Date
This patch fixes a bug in ordered_event.c:alloc_event().
An ordered_event struct was not initialized properly potentially
causing crashes later on in free_dup_event() depending on the
content of the memory. If it was NULL, then it would work fine,
otherwise, it could cause crashes such as:

$ perf record -o - -e cycles date | perf inject -b -i - >/dev/null
Tue Aug 7 12:03:48 PDT 2018
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.000 MB - ]
Segmentation fault (core dumped):

(gdb) r inject -b -i - < tt >/dev/null
Program received signal SIGSEGV, Segmentation fault.
free_dup_event (oe=0x26a39a0, event=0xffffffff00000000) at util/ordered-events.c:85
(gdb) bt
#0 free_dup_event (oe=0x26a39a0, event=0xffffffff00000000) at util/ordered-events.c:85
#1 ordered_events__free (oe=0x26a39a0) at util/ordered-events.c:310
#2 0x00000000004b5a56 in __perf_session__process_pipe_events (session=<optimized out>) at util/session.c:1753
#3 perf_session__process_events (session=<optimized out>) at util/session.c:1932
#4 0x000000000043a2eb in __cmd_inject (inject=<optimized out>) at builtin-inject.c:750
#5 cmd_inject (argc=<optimized out>, argv=<optimized out>) at builtin-inject.c:924
#6 0x000000000046b175 in run_builtin (p=0xabc640 <commands+576>, argc=4, argv=0x7fffffffe560) at perf.c:297
#7 0x000000000046b062 in handle_internal_command (argc=4, argv=0x7fffffffe560) at perf.c:349
#8 0x000000000046a5e8 in run_argv (argcp=<optimized out>, argv=<optimized out>) at perf.c:393
#9 main (argc=4, argv=0x7fffffffe560) at perf.c:531

Signed-off-by: Stephane Eranian <eranian@google.com>

---
tools/perf/util/ordered-events.c | 6 ++++++
1 file changed, 6 insertions(+)

diff --git a/tools/perf/util/ordered-events.c b/tools/perf/util/ordered-events.c
index a90dbe5df019..95c91e5a3754 100644
--- a/tools/perf/util/ordered-events.c
+++ b/tools/perf/util/ordered-events.c
@@ -118,6 +118,12 @@ static struct ordered_event *alloc_event(struct ordered_events *oe,

pr("alloc size %" PRIu64 "B (+%zu), max %" PRIu64 "B\n",
oe->cur_alloc_size, size, oe->max_alloc_size);
+ /*
+ * must initialize event pointer of commandeered first
+ * entry to avoid crash in free_dup_event() due to random
+ * value for this field.
+ */
+ oe->buffer->event = NULL;

oe->cur_alloc_size += size;
list_add(&oe->buffer->list, &oe->to_free);
--
2.18.0.597.ga71716f1ad-goog
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