[tip:perf/core] perf trace: Check for vfs_getname.pathname length

[tip-bot for Arnaldo Carvalho de Melo <tipbot@zytor.com>]

Commit-ID:  39f0e7a825cfc971dc9ad40b0770c22f6f4f89b8
Gitweb:     http://git.kernel.org/tip/39f0e7a825cfc971dc9ad40b0770c22f6f4f89b8
Author:     Arnaldo Carvalho de Melo <acme@redhat.com>
AuthorDate: Fri, 24 Mar 2017 14:51:28 -0300
Committer:  Arnaldo Carvalho de Melo <acme@redhat.com>
CommitDate: Fri, 24 Mar 2017 16:05:31 -0300

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>
---
 tools/perf/builtin-trace.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c
index 912fedc..33c657c 100644
--- 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);