[PATCH 11/11] setfiles: avoid unsigned integer underflow

["Christian Göttsche" <cgzones@googlemail.com>]

While well-defined unsigned integer underflow might signal a logic
mistake or processing of unchecked user input.  Please Clang's undefined
behavior sanitizer:

    restore.c:91:37: runtime error: unsigned integer overflow: 1 - 2 cannot be represented in type 'unsigned long'

Signed-off-by: Christian Göttsche <cgzones@googlemail.com>
---
 policycoreutils/setfiles/restore.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/policycoreutils/setfiles/restore.c b/policycoreutils/setfiles/restore.c
index 6131f46a..d045e948 100644
--- a/policycoreutils/setfiles/restore.c
+++ b/policycoreutils/setfiles/restore.c
@@ -77,8 +77,8 @@ int process_glob(char *name, struct restore_opts *opts, size_t nthreads,
 		 long unsigned *skipped_errors)
 {
 	glob_t globbuf;
-	size_t i = 0;
-	int len, rc, errors;
+	size_t i, len;
+	int rc, errors;
 
 	memset(&globbuf, 0, sizeof(globbuf));
 
@@ -88,10 +88,10 @@ int process_glob(char *name, struct restore_opts *opts, size_t nthreads,
 		return errors;
 
 	for (i = 0; i < globbuf.gl_pathc; i++) {
-		len = strlen(globbuf.gl_pathv[i]) - 2;
-		if (len > 0 && strcmp(&globbuf.gl_pathv[i][len--], "/.") == 0)
+		len = strlen(globbuf.gl_pathv[i]);
+		if (len > 2 && strcmp(&globbuf.gl_pathv[i][len - 2], "/.") == 0)
 			continue;
-		if (len > 0 && strcmp(&globbuf.gl_pathv[i][len], "/..") == 0)
+		if (len > 3 && strcmp(&globbuf.gl_pathv[i][len - 3], "/..") == 0)
 			continue;
 		rc = selinux_restorecon_parallel(globbuf.gl_pathv[i],
 						 opts->restorecon_flags,
-- 
2.43.0