[PATCH] perf: buildid-cache zero out buffer of filenames when adding/remoing buildid

[Han Pingtian <phan@redhat.com>]

readlink() doesn't append a null byte to buf. So we should zero out buf
with zalloc(). Or we'll see sometimes error like this:

[root@intel-s3e36-01]~# /usr/bin/perf buildid-cache -a /lib/modules/2.6.32-130.el6.x86_64/kernel/crypto/twofish_common.ko -v
Adding f64ba8efd5f53c7ad332fc17db1d21de309038e1 /lib/modules/2.6.32-130.el6.x86_64/kernel/crypto/twofish_common.ko: Ok
[root@intel-s3e36-01]~# /usr/bin/perf buildid-cache -r /lib/modules/2.6.32-130.el6.x86_64/kernel/crypto/twofish_common.ko -v
Removing f64ba8efd5f53c7ad332fc17db1d21de309038e1 /lib/modules/2.6.32-130.el6.x86_64/kernel/crypto/twofish_common.ko: FAIL
/lib/modules/2.6.32-130.el6.x86_64/kernel/crypto/twofish_common.ko wasn't in the cache

The change in build_id_cache__add_s() is a defense.

Signed-off-by: Han Pingtian <phan@redhat.com>
---
 tools/perf/util/header.c |    8 ++++----
 1 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
index afb0849..36d723d 100644
--- a/tools/perf/util/header.c
+++ b/tools/perf/util/header.c
@@ -189,8 +189,8 @@ int build_id_cache__add_s(const char *sbuild_id, const char *debugdir,
 			  const char *name, bool is_kallsyms)
 {
 	const size_t size = PATH_MAX;
-	char *realname, *filename = malloc(size),
-	     *linkname = malloc(size), *targetname;
+	char *realname, *filename = zalloc(size),
+	     *linkname = zalloc(size), *targetname;
 	int len, err = -1;
 
 	if (is_kallsyms) {
@@ -254,8 +254,8 @@ static int build_id_cache__add_b(const u8 *build_id, size_t build_id_size,
 int build_id_cache__remove_s(const char *sbuild_id, const char *debugdir)
 {
 	const size_t size = PATH_MAX;
-	char *filename = malloc(size),
-	     *linkname = malloc(size);
+	char *filename = zalloc(size),
+	     *linkname = zalloc(size);
 	int err = -1;
 
 	if (filename == NULL || linkname == NULL)
-- 
1.7.1