[PATCH 1/2] libselinux: fix segfault in add_xattr_entry()

[Petr Lautrbach <plautrba@xxxxxxxxxx>]

When selabel_get_digests_all_partial_matches(), resp
get_digests_all_partial_matches() doesn't find a match,
calculated_digest is not initialized and followup memcmp() could
segfault. Given that calculated_digest and xattr_digest are already
compared in get_digests_all_partial_matches() and the function returns
true or false based on this comparison, it's not neccessary to compare
these values again.

Fixes:
    # restorecon_xattr -d -v tmp
    specfiles SHA1 digest: afc752f47d489f3e82ac1da8fd247a2e1a6af5f8
    calculated using the following specfile(s):
    /etc/selinux/targeted/contexts/files/file_contexts.subs_dist
    /etc/selinux/targeted/contexts/files/file_contexts.subs
    /etc/selinux/targeted/contexts/files/file_contexts.bin
    /etc/selinux/targeted/contexts/files/file_contexts.homedirs.bin
    /etc/selinux/targeted/contexts/files/file_contexts.local.bin

    Segmentation fault (core dumped)

Signed-off-by: Petr Lautrbach <plautrba@xxxxxxxxxx>
---
 libselinux/src/selinux_restorecon.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/libselinux/src/selinux_restorecon.c b/libselinux/src/selinux_restorecon.c
index 6993be6fda17..4bca29b9de78 100644
--- a/libselinux/src/selinux_restorecon.c
+++ b/libselinux/src/selinux_restorecon.c
@@ -297,6 +297,7 @@ static int add_xattr_entry(const char *directory, bool delete_nonmatch,
 	char *sha1_buf = NULL;
 	size_t i, digest_len = 0;
 	int rc, digest_result;
+	bool match;
 	struct dir_xattr *new_entry;
 	uint8_t *xattr_digest = NULL;
 	uint8_t *calculated_digest = NULL;
@@ -306,7 +307,7 @@ static int add_xattr_entry(const char *directory, bool delete_nonmatch,
 		return -1;
 	}
 
-	selabel_get_digests_all_partial_matches(fc_sehandle, directory,
+	match = selabel_get_digests_all_partial_matches(fc_sehandle, directory,
 						&calculated_digest,
 						&xattr_digest, &digest_len);
 
@@ -326,11 +327,10 @@ static int add_xattr_entry(const char *directory, bool delete_nonmatch,
 	for (i = 0; i < digest_len; i++)
 		sprintf((&sha1_buf[i * 2]), "%02x", xattr_digest[i]);
 
-	rc = memcmp(calculated_digest, xattr_digest, digest_len);
-	digest_result = rc ? NOMATCH : MATCH;
+	digest_result = match ? MATCH : NOMATCH;
 
-	if ((delete_nonmatch && rc != 0) || delete_all) {
-		digest_result = rc ? DELETED_NOMATCH : DELETED_MATCH;
+	if ((delete_nonmatch && ! match) || delete_all) {
+		digest_result = match ? DELETED_MATCH : DELETED_NOMATCH;
 		rc = removexattr(directory, RESTORECON_PARTIAL_MATCH_DIGEST);
 		if (rc) {
 			selinux_log(SELINUX_ERROR,
-- 
2.30.1