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Subject[PATCH 119/161] perf evlist: Fix perf_evlist__mmap_read event overflow
Date
From: Jiri Olsa <jolsa@redhat.com>

The perf_evlist__mmap_read used 'union perf_event' as a placeholder for
event crossing the mmap boundary.

This is ok for sample shorter than ~PATH_MAX. However we could grow up
to the maximum sample size which is 16 bits max.

I hit this overflow issue when using 'perf top -G dwarf' which produces
sample with the size around 8192 bytes. We could configure any valid
sample size here using: '-G dwarf,size'.

Using array with sample max size instead for the event placeholder. Also
adding another safe check for the dynamic size of the user stack.

TODO: The 'struct perf_mmap' is quite big now, maybe we could use some
lazy allocation for event_copy size.

Signed-off-by: Jiri Olsa <jolsa@redhat.com>
Acked-by: David Ahern <dsahern@gmail.com>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1380721599-24285-1-git-send-email-jolsa@redhat.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
tools/perf/util/event.h | 3 +++
tools/perf/util/evlist.c | 4 ++--
tools/perf/util/evlist.h | 2 +-
tools/perf/util/evsel.c | 3 +++
4 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/tools/perf/util/event.h b/tools/perf/util/event.h
index 9b7d4d333111..752709ccfb00 100644
--- a/tools/perf/util/event.h
+++ b/tools/perf/util/event.h
@@ -75,6 +75,9 @@ struct throttle_event {
PERF_SAMPLE_CPU | PERF_SAMPLE_PERIOD | \
PERF_SAMPLE_IDENTIFIER)

+/* perf sample has 16 bits size limit */
+#define PERF_SAMPLE_MAX_SIZE (1 << 16)
+
struct sample_event {
struct perf_event_header header;
u64 array[];
diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
index f0d71a9d49f4..cb9523f50a37 100644
--- a/tools/perf/util/evlist.c
+++ b/tools/perf/util/evlist.c
@@ -540,7 +540,7 @@ union perf_event *perf_evlist__mmap_read(struct perf_evlist *evlist, int idx)
if ((old & md->mask) + size != ((old + size) & md->mask)) {
unsigned int offset = old;
unsigned int len = min(sizeof(*event), size), cpy;
- void *dst = &md->event_copy;
+ void *dst = md->event_copy;

do {
cpy = min(md->mask + 1 - (offset & md->mask), len);
@@ -550,7 +550,7 @@ union perf_event *perf_evlist__mmap_read(struct perf_evlist *evlist, int idx)
len -= cpy;
} while (len);

- event = &md->event_copy;
+ event = (union perf_event *) md->event_copy;
}

old += size;
diff --git a/tools/perf/util/evlist.h b/tools/perf/util/evlist.h
index 871b55ab5dee..722618f84c53 100644
--- a/tools/perf/util/evlist.h
+++ b/tools/perf/util/evlist.h
@@ -21,7 +21,7 @@ struct perf_mmap {
void *base;
int mask;
unsigned int prev;
- union perf_event event_copy;
+ char event_copy[PERF_SAMPLE_MAX_SIZE];
};

struct perf_evlist {
diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index abe69af58b62..bfebc1ea3c51 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -1456,6 +1456,9 @@ int perf_evsel__parse_sample(struct perf_evsel *evsel, union perf_event *event,
array = (void *)array + sz;
OVERFLOW_CHECK_u64(array);
data->user_stack.size = *array++;
+ if (WARN_ONCE(data->user_stack.size > sz,
+ "user stack dump failure\n"))
+ return -EFAULT;
}
}

--
1.8.1.4


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