[PATCH 1/4] libselinux: avoid errno modification by fclose(3)

[Christian Göttsche <cgoettsche@xxxxxxxxxxxxx>]

From: Christian Göttsche <cgzones@xxxxxxxxxxxxxx>

In case fclose(3) might modify the global variable errno, use a wrapper
retaining the errno value.  In the affected cases the success of
fclose(3) itself is not important, since the underlying descriptor is
only read from.

Reported-by: clang-analyzer
Signed-off-by: Christian Göttsche <cgzones@xxxxxxxxxxxxxx>
---
 libselinux/src/get_context_list.c |  4 ++--
 libselinux/src/label_file.c       |  4 ++--
 libselinux/src/selinux_internal.h | 11 +++++++++++
 3 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/libselinux/src/get_context_list.c b/libselinux/src/get_context_list.c
index 0ad24654..222b54c1 100644
--- a/libselinux/src/get_context_list.c
+++ b/libselinux/src/get_context_list.c
@@ -438,7 +438,7 @@ int get_ordered_context_list(const char *user,
 		__fsetlocking(fp, FSETLOCKING_BYCALLER);
 		rc = get_context_user(fp, con, user, &reachable, &nreachable);
 
-		fclose(fp);
+		fclose_errno_safe(fp);
 		if (rc < 0 && errno != ENOENT) {
 			selinux_log(SELINUX_ERROR,
 				"%s:  error in processing configuration file %s\n",
@@ -451,7 +451,7 @@ int get_ordered_context_list(const char *user,
 	if (fp) {
 		__fsetlocking(fp, FSETLOCKING_BYCALLER);
 		rc = get_context_user(fp, con, user, &reachable, &nreachable);
-		fclose(fp);
+		fclose_errno_safe(fp);
 		if (rc < 0 && errno != ENOENT) {
 			selinux_log(SELINUX_ERROR,
 				"%s:  error in processing configuration file %s\n",
diff --git a/libselinux/src/label_file.c b/libselinux/src/label_file.c
index 2fad0c93..40628e2c 100644
--- a/libselinux/src/label_file.c
+++ b/libselinux/src/label_file.c
@@ -628,7 +628,7 @@ static int process_file(const char *path, const char *suffix,
 
 		rc = fcontext_is_binary(fp);
 		if (rc < 0) {
-			(void) fclose(fp);
+			fclose_errno_safe(fp);
 			return -1;
 		}
 
@@ -639,7 +639,7 @@ static int process_file(const char *path, const char *suffix,
 			rc = digest_add_specfile(digest, fp, NULL, sb.st_size,
 				found_path);
 
-		fclose(fp);
+		fclose_errno_safe(fp);
 
 		if (!rc)
 			return 0;
diff --git a/libselinux/src/selinux_internal.h b/libselinux/src/selinux_internal.h
index 450a42c2..372837dd 100644
--- a/libselinux/src/selinux_internal.h
+++ b/libselinux/src/selinux_internal.h
@@ -2,7 +2,9 @@
 #define SELINUX_INTERNAL_H_
 
 #include <selinux/selinux.h>
+#include <errno.h>
 #include <pthread.h>
+#include <stdio.h>
 
 
 extern int require_seusers ;
@@ -131,4 +133,13 @@ void *reallocarray(void *ptr, size_t nmemb, size_t size);
 #define IGNORE_DEPRECATED_DECLARATION_END
 #endif
 
+static inline void fclose_errno_safe(FILE *stream)
+{
+	int saved_errno;
+
+	saved_errno = errno;
+	(void) fclose(stream);
+	errno = saved_errno;
+}
+
 #endif /* SELINUX_INTERNAL_H_ */
-- 
2.45.2