[PATCH] libselinux: preserve errno in selinux_log()

[Christian Göttsche <cgzones@xxxxxxxxxxxxxx>]

selinux_log() is used in many error branches, where the caller might
expect errno to bet set, e.g. label_file.c::lookup_all():

    if (match_count) {
		*match_count = 0;
		result = calloc(data->nspec, sizeof(struct spec*));
	} else {
		result = calloc(1, sizeof(struct spec*));
	}
	if (!result) {
		selinux_log(SELINUX_ERROR, "Failed to allocate %zu bytes of data\n",
			    data->nspec * sizeof(struct spec*));
		goto finish;
	}

Preserve errno in the macro wrapper itself, also preventing accidental
errno modifications in client specified SELINUX_CB_LOG callbacks.

Signed-off-by: Christian Göttsche <cgzones@xxxxxxxxxxxxxx>
---
 libselinux/src/callbacks.h              | 3 +++
 libselinux/src/label_backends_android.c | 2 --
 libselinux/src/label_file.h             | 2 --
 libselinux/src/selinux_restorecon.c     | 6 +-----
 4 files changed, 4 insertions(+), 9 deletions(-)

diff --git a/libselinux/src/callbacks.h b/libselinux/src/callbacks.h
index f4dab157..5a4d0f8a 100644
--- a/libselinux/src/callbacks.h
+++ b/libselinux/src/callbacks.h
@@ -5,6 +5,7 @@
 #ifndef _SELINUX_CALLBACKS_H_
 #define _SELINUX_CALLBACKS_H_
 
+#include <errno.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
@@ -32,9 +33,11 @@ extern int
 extern pthread_mutex_t log_mutex;
 
 #define selinux_log(type, ...) do { \
+	int saved_errno__ = errno; \
 	__pthread_mutex_lock(&log_mutex); \
 	selinux_log_direct(type, __VA_ARGS__); \
 	__pthread_mutex_unlock(&log_mutex); \
+	errno = saved_errno__; \
 } while(0)
 
 #endif				/* _SELINUX_CALLBACKS_H_ */
diff --git a/libselinux/src/label_backends_android.c b/libselinux/src/label_backends_android.c
index 66d4df2d..c2d78360 100644
--- a/libselinux/src/label_backends_android.c
+++ b/libselinux/src/label_backends_android.c
@@ -93,7 +93,6 @@ static int process_line(struct selabel_handle *rec,
 
 	items = read_spec_entries(line_buf, &errbuf, 2, &prop, &context);
 	if (items < 0) {
-		items = errno;
 		if (errbuf) {
 			selinux_log(SELINUX_ERROR,
 				    "%s:  line %u error due to: %s\n", path,
@@ -103,7 +102,6 @@ static int process_line(struct selabel_handle *rec,
 				    "%s:  line %u error due to: %m\n", path,
 				    lineno);
 		}
-		errno = items;
 		return -1;
 	}
 
diff --git a/libselinux/src/label_file.h b/libselinux/src/label_file.h
index b453e13f..190bc175 100644
--- a/libselinux/src/label_file.h
+++ b/libselinux/src/label_file.h
@@ -444,7 +444,6 @@ static inline int process_line(struct selabel_handle *rec,
 
 	items = read_spec_entries(line_buf, &errbuf, 3, &regex, &type, &context);
 	if (items < 0) {
-		rc = errno;
 		if (errbuf) {
 			selinux_log(SELINUX_ERROR,
 				    "%s:  line %u error due to: %s\n", path,
@@ -454,7 +453,6 @@ static inline int process_line(struct selabel_handle *rec,
 				    "%s:  line %u error due to: %m\n", path,
 				    lineno);
 		}
-		errno = rc;
 		return -1;
 	}
 
diff --git a/libselinux/src/selinux_restorecon.c b/libselinux/src/selinux_restorecon.c
index e6192912..ba7b3692 100644
--- a/libselinux/src/selinux_restorecon.c
+++ b/libselinux/src/selinux_restorecon.c
@@ -1032,7 +1032,7 @@ static int selinux_restorecon_common(const char *pathname_orig,
 	struct stat sb;
 	char *pathname = NULL, *pathdnamer = NULL, *pathdname, *pathbname;
 	char *paths[2] = { NULL, NULL };
-	int fts_flags, error, sverrno;
+	int fts_flags, error;
 	struct dir_hash_node *current = NULL;
 
 	if (state.flags.verbose && state.flags.progress)
@@ -1286,18 +1286,14 @@ cleanup:
 	return error;
 
 oom:
-	sverrno = errno;
 	selinux_log(SELINUX_ERROR, "%s:  Out of memory\n", __func__);
-	errno = sverrno;
 	error = -1;
 	goto cleanup;
 
 realpatherr:
-	sverrno = errno;
 	selinux_log(SELINUX_ERROR,
 		    "SELinux: Could not get canonical path for %s restorecon: %m.\n",
 		    pathname_orig);
-	errno = sverrno;
 	error = -1;
 	goto cleanup;
 
-- 
2.36.1