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>

7 files changed, 43 insertions, 14 deletions

diff --git a/lib/libalpm/be_local.c b/lib/libalpm/be_local.c
index 1b333e44..091ed4c8 100644
--- a/lib/libalpm/be_local.c
+++ b/lib/libalpm/be_local.c
@@ -616,7 +616,7 @@ char *_alpm_local_db_pkgpath(alpm_db_t *db, alpm_pkg_t *info,
 }
 
 #define READ_NEXT() do { \
-	if(fgets(line, sizeof(line), fp) == NULL && !feof(fp)) goto error; \
+	if(safe_fgets(line, sizeof(line), fp) == NULL && !feof(fp)) goto error; \
 	_alpm_strip_newline(line, 0); \
 } while(0)
 
@@ -627,7 +627,7 @@ char *_alpm_local_db_pkgpath(alpm_db_t *db, alpm_pkg_t *info,
 
 #define READ_AND_STORE_ALL(f) do { \
 	char *linedup; \
-	if(fgets(line, sizeof(line), fp) == NULL) {\
+	if(safe_fgets(line, sizeof(line), fp) == NULL) {\
 		if(!feof(fp)) goto error; else break; \
 	} \
 	if(_alpm_strip_newline(line, 0) == 0) break; \
@@ -636,7 +636,7 @@ char *_alpm_local_db_pkgpath(alpm_db_t *db, alpm_pkg_t *info,
 } while(1) /* note the while(1) and not (0) */
 
 #define READ_AND_SPLITDEP(f) do { \
-	if(fgets(line, sizeof(line), fp) == NULL) {\
+	if(safe_fgets(line, sizeof(line), fp) == NULL) {\
 		if(!feof(fp)) goto error; else break; \
 	} \
 	if(_alpm_strip_newline(line, 0) == 0) break; \
@@ -682,7 +682,7 @@ static int local_db_read(alpm_pkg_t *info, alpm_dbinfrq_t inforeq)
 		}
 		free(path);
 		while(!feof(fp)) {
-			if(fgets(line, sizeof(line), fp) == NULL && !feof(fp)) {
+			if(safe_fgets(line, sizeof(line), fp) == NULL && !feof(fp)) {
 				goto error;
 			}
 			if(_alpm_strip_newline(line, 0) == 0) {
@@ -771,13 +771,13 @@ static int local_db_read(alpm_pkg_t *info, alpm_dbinfrq_t inforeq)
 			goto error;
 		}
 		free(path);
-		while(fgets(line, sizeof(line), fp)) {
+		while(safe_fgets(line, sizeof(line), fp)) {
 			_alpm_strip_newline(line, 0);
 			if(strcmp(line, "%FILES%") == 0) {
 				size_t files_count = 0, files_size = 0, len;
 				alpm_file_t *files = NULL;
 
-				while(fgets(line, sizeof(line), fp) &&
+				while(safe_fgets(line, sizeof(line), fp) &&
 						(len = _alpm_strip_newline(line, 0))) {
 					if(!_alpm_greedy_grow((void **)&files, &files_size,
 								(files_size ? files_size + sizeof(alpm_file_t) : 8 * sizeof(alpm_file_t)))) {
@@ -797,7 +797,7 @@ static int local_db_read(alpm_pkg_t *info, alpm_dbinfrq_t inforeq)
 				info->files.count = files_count;
 				info->files.files = files;
 			} else if(strcmp(line, "%BACKUP%") == 0) {
-				while(fgets(line, sizeof(line), fp) && _alpm_strip_newline(line, 0)) {
+				while(safe_fgets(line, sizeof(line), fp) && _alpm_strip_newline(line, 0)) {
 					alpm_backup_t *backup;
 					CALLOC(backup, 1, sizeof(alpm_backup_t), goto error);
 					if(_alpm_split_backup(line, &backup)) {
diff --git a/lib/libalpm/trans.c b/lib/libalpm/trans.c
index 4a176086..aebd8dd2 100644
--- a/lib/libalpm/trans.c
+++ b/lib/libalpm/trans.c
@@ -280,7 +280,7 @@ static int grep(const char *fn, const char *needle)
 	}
 	while(!feof(fp)) {
 		char line[1024];
-		if(fgets(line, sizeof(line), fp) == NULL) {
+		if(safe_fgets(line, sizeof(line), fp) == NULL) {
 			continue;
 		}
 		/* TODO: this will not work if the search string
diff --git a/lib/libalpm/util.c b/lib/libalpm/util.c
index 6dab0de2..43d0d7be 100644
--- a/lib/libalpm/util.c
+++ b/lib/libalpm/util.c
@@ -576,8 +576,9 @@ int _alpm_run_chroot(alpm_handle_t *handle, const char *cmd, char *const argv[])
 					.type = ALPM_EVENT_SCRIPTLET_INFO,
 					.line = line
 				};
-				if(fgets(line, PATH_MAX, pipe_file) == NULL)
+				if(safe_fgets(line, PATH_MAX, pipe_file) == NULL) {
 					break;
+				}
 				alpm_logaction(handle, "ALPM-SCRIPTLET", "%s", line);
 				EVENT(handle, &event);
 			}
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;