[PATCH 4/5] perf session: Fix perf_session__peek_event()

From: Adrian Hunter
Date: Tue May 19 2015 - 09:08:37 EST


perf_session__peek_event() generally leverages there
being a single mmap of the perf.data file, however on
32-bit platforms when there is more that 32MiB of
data, then there are multiple mmaps, so
perf_session__peek_event() reads from the file.

In that case a couple of bugs were exposed (note
how the seg. fault appears with >32M of data):

$ perf record --per-thread -e intel_bts// ../rtit-tests/loopy 1000000
[ perf record: Woken up 13 times to write data ]
[ perf record: Captured and wrote 24.568 MB perf.data ]
$ perf script > /dev/null
$ perf record --per-thread -e intel_bts// ../rtit-tests/loopy 10000000
[ perf record: Woken up 136 times to write data ]
[ perf record: Captured and wrote 270.794 MB perf.data ]
$ perf script > /dev/null
Segmentation fault (core dumped)

The wrong address was being passed to the readn() function and
the buffer size was not being checked.

Signed-off-by: Adrian Hunter <adrian.hunter@xxxxxxxxx>
---
tools/perf/util/session.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c
index e722107..39fe09d 100644
--- a/tools/perf/util/session.c
+++ b/tools/perf/util/session.c
@@ -1182,7 +1182,7 @@ int perf_session__peek_event(struct perf_session *session, off_t file_offset,
return -1;

if (lseek(fd, file_offset, SEEK_SET) == (off_t)-1 ||
- readn(fd, &buf, hdr_sz) != (ssize_t)hdr_sz)
+ readn(fd, buf, hdr_sz) != (ssize_t)hdr_sz)
return -1;

event = (union perf_event *)buf;
@@ -1190,12 +1190,12 @@ int perf_session__peek_event(struct perf_session *session, off_t file_offset,
if (session->header.needs_swap)
perf_event_header__bswap(&event->header);

- if (event->header.size < hdr_sz)
+ if (event->header.size < hdr_sz || event->header.size > buf_sz)
return -1;

rest = event->header.size - hdr_sz;

- if (readn(fd, &buf, rest) != (ssize_t)rest)
+ if (readn(fd, buf, rest) != (ssize_t)rest)
return -1;

if (session->header.needs_swap)
--
1.9.1

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