perf evlist: Fix perf_evlist__mmap_read event overflow

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>

diff --git a/tools/perf/util/event.h b/tools/perf/util/event.h
index 9b7d4d3..752709c 100644 (file)
--- 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 f0d71a9..cb9523f 100644 (file)
--- 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 871b55a..722618f 100644 (file)
--- 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 abe69af..bfebc1e 100644 (file)
--- 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;
                }
        }