From: Numfor Mbiziwo-Tiapo nums@google.com
[ Upstream commit 20f9781f491360e7459c589705a2e4b1f136bee9 ]
When building our local version of perf with MSAN (Memory Sanitizer) and running the perf record command, MSAN throws a use of uninitialized value warning in "tools/perf/util/util.c:333:6".
This warning stems from the "buf" variable being passed into "write". It originated as the variable "ev" with the type union perf_event* defined in the "perf_event__synthesize_attr" function in "tools/perf/util/header.c".
In the "perf_event__synthesize_attr" function they allocate space with a malloc call using ev, then go on to only assign some of the member variables before passing "ev" on as a parameter to the "process" function therefore "ev" contains uninitialized memory. Changing the malloc call to zalloc to initialize all the members of "ev" which gets rid of the warning.
To reproduce this warning, build perf by running: make -C tools/perf CLANG=1 CC=clang EXTRA_CFLAGS="-fsanitize=memory\ -fsanitize-memory-track-origins"
(Additionally, llvm might have to be installed and clang might have to be specified as the compiler - export CC=/usr/bin/clang)
then running: tools/perf/perf record -o - ls / | tools/perf/perf --no-pager annotate\ -i - --stdio
Please see the cover letter for why false positive warnings may be generated.
Signed-off-by: Numfor Mbiziwo-Tiapo nums@google.com Cc: Alexander Shishkin alexander.shishkin@linux.intel.com Cc: Ian Rogers irogers@google.com Cc: Jiri Olsa jolsa@redhat.com Cc: Mark Drayton mbd@fb.com Cc: Namhyung Kim namhyung@kernel.org Cc: Peter Zijlstra peterz@infradead.org Cc: Song Liu songliubraving@fb.com Cc: Stephane Eranian eranian@google.com Link: http://lkml.kernel.org/r/20190724234500.253358-2-nums@google.com Signed-off-by: Arnaldo Carvalho de Melo acme@redhat.com Signed-off-by: Sasha Levin sashal@kernel.org --- tools/perf/util/header.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c index 0102dd46fb6da..bcb8e85a40f90 100644 --- a/tools/perf/util/header.c +++ b/tools/perf/util/header.c @@ -2680,7 +2680,7 @@ int perf_event__synthesize_attr(struct perf_tool *tool, size += sizeof(struct perf_event_header); size += ids * sizeof(u64);
- ev = malloc(size); + ev = zalloc(size);
if (ev == NULL) return -ENOMEM;