Em Wed, Jul 24, 2019 at 04:44:58PM -0700, Numfor Mbiziwo-Tiapo escreveu: > 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 calloc initializes all the members of "ev" which gets rid of the > warning.
I'm applying, but changing the calloc call to zalloc() that is just a shorter wrapper to calloc(1, size). Thanks, - Arnaldo > 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 <n...@google.com> > --- > 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 dec6d218c31c..b9c71fc45ac1 100644 > --- a/tools/perf/util/header.c > +++ b/tools/perf/util/header.c > @@ -3427,7 +3427,7 @@ int perf_event__synthesize_attr(struct perf_tool *tool, > size += sizeof(struct perf_event_header); > size += ids * sizeof(u64); > > - ev = malloc(size); > + ev = calloc(1, size); > > if (ev == NULL) > return -ENOMEM; > -- > 2.22.0.657.g960e92d24f-goog -- - Arnaldo
