wrap fgets to retry on EINTR

The read() underlying fgets() can be interrupted by a signal handler
causing fgets() to return NULL.  Before we started handling SIGWINCH,
the odds of interrupting a read were low and typically resulted in
termination anyway.  Replace all fgets calls with a wrapper that retries
in EINTR.

Signed-off-by: Andrew Gregory <andrew.gregory.8@gmail.com>

4 files changed, 33 insertions, 5 deletions

diff --git a/src/common/util-common.c b/src/common/util-common.c
index 3316eaec..ab74e7c6 100644
--- a/src/common/util-common.c
+++ b/src/common/util-common.c
@@ -17,6 +17,7 @@
  *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
+#include <errno.h>
 #include <stdlib.h>
 #include <string.h>
 
@@ -102,6 +103,30 @@ int llstat(char *path, struct stat *buf)
 	return ret;
 }
 
+/** Wrapper around fgets() which properly handles EINTR
+ * @param s string to read into
+ * @param size maximum length to read
+ * @param stream stream to read from
+ * @return value returned by fgets()
+ */
+char *safe_fgets(char *s, int size, FILE *stream)
+{
+	char *ret;
+	int errno_save = errno, ferror_save = ferror(stream);
+	while((ret = fgets(s, size, stream)) == NULL && !feof(stream)) {
+		if(errno == EINTR) {
+			/* clear any errors we set and try again */
+			errno = errno_save;
+			if(!ferror_save) {
+				clearerr(stream);
+			}
+		} else {
+			break;
+		}
+	}
+	return ret;
+}
+
 #ifndef HAVE_STRNDUP
 /* A quick and dirty implementation derived from glibc */
 /** Determines the length of a fixed-size string.
diff --git a/src/common/util-common.h b/src/common/util-common.h
index 576702fa..ca8db5ab 100644
--- a/src/common/util-common.h
+++ b/src/common/util-common.h
@@ -20,6 +20,7 @@
 #ifndef _PM_UTIL_COMMON_H
 #define _PM_UTIL_COMMON_H
 
+#include <stdio.h>
 #include <sys/stat.h> /* struct stat */
 
 const char *mbasename(const char *path);
@@ -27,6 +28,8 @@ char *mdirname(const char *path);
 
 int llstat(char *path, struct stat *buf);
 
+char *safe_fgets(char *s, int size, FILE *stream);
+
 #ifndef HAVE_STRNDUP
 char *strndup(const char *s, size_t n);
 #endif
diff --git a/src/pacman/ini.c b/src/pacman/ini.c
index 2a3ef0ed..2eb32302 100644
--- a/src/pacman/ini.c
+++ b/src/pacman/ini.c
@@ -66,7 +66,7 @@ static int _parse_ini(const char *file, ini_parser_fn cb, void *data,
 		goto cleanup;
 	}
 
-	while(fgets(line, PATH_MAX, fp)) {
+	while(safe_fgets(line, PATH_MAX, fp)) {
 		char *key, *value, *ptr;
 		size_t line_len;
 
diff --git a/src/pacman/util.c b/src/pacman/util.c
index 6a095fdb..2671e54c 100644
--- a/src/pacman/util.c
+++ b/src/pacman/util.c
@@ -1403,7 +1403,7 @@ int multiselect_question(char *array, int count)
 
 		flush_term_input(fileno(stdin));
 
-		if(fgets(response, response_len, stdin)) {
+		if(safe_fgets(response, response_len, stdin)) {
 			const size_t response_incr = 64;
 			size_t len;
 			/* handle buffer not being large enough to read full line case */
@@ -1416,7 +1416,7 @@ int multiselect_question(char *array, int count)
 				lastchar = response + response_len - 1;
 				/* sentinel byte */
 				*lastchar = 1;
-				if(fgets(response + response_len - response_incr - 1,
+				if(safe_fgets(response + response_len - response_incr - 1,
 							response_incr + 1, stdin) == 0) {
 					free(response);
 					return -1;
@@ -1467,7 +1467,7 @@ int select_question(int count)
 
 		flush_term_input(fileno(stdin));
 
-		if(fgets(response, sizeof(response), stdin)) {
+		if(safe_fgets(response, sizeof(response), stdin)) {
 			size_t len = strtrim(response);
 			if(len > 0) {
 				int n;
@@ -1521,7 +1521,7 @@ static int question(short preset, const char *format, va_list args)
 
 	flush_term_input(fd_in);
 
-	if(fgets(response, sizeof(response), stdin)) {
+	if(safe_fgets(response, sizeof(response), stdin)) {
 		size_t len = strtrim(response);
 		if(len == 0) {
 			return preset;