perf trace: Check for vfs_getname.pathname length

It shouldn't be zero, but if the 'perf probe' on getname_flags() (or
elsewhere in the future we need to probe to catch the pathname for
syscalls like 'open' being copied from userspace to the kernel) is
misplaced somehow, then we will end up not allocating space and trying
to copy the "" empty string to ttrace->filename.name, causing a
segfault, fix it.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/n/tip-c4f1t6sx1nczuzop19r5si5s@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c
index 912fedc5b42d0eb7cff554fa6d80e16c704894f2..33c657c15d5e72e363b8cb980231e0c45250f983 100644 (file)
--- a/tools/perf/builtin-trace.c
+++ b/tools/perf/builtin-trace.c
@@ -1656,6 +1656,8 @@ static int trace__vfs_getname(struct trace *trace, struct perf_evsel *evsel,
                goto out;
 
        filename_len = strlen(filename);
+       if (filename_len == 0)
+               goto out;
 
        if (ttrace->filename.namelen < filename_len) {
                char *f = realloc(ttrace->filename.name, filename_len + 1);