Initial guard against pathconf() returning -1 for whatever reason

1 files changed, 25 insertions, 5 deletions

diff --git a/luxio.c b/luxio.c
index 8ec0727..fd6876e 100644
--- a/luxio.c
+++ b/luxio.c
@@ -71,6 +71,26 @@ Not all systems will provide all the functions described here.
 
 #define INVALID_MODE ((mode_t) -1)
 
+/* Internal helper functions *************************************************/
+
+#define LUXIO_MIN_PATHSIZE 4096
+
+static int safe_pathconf(const char *path, int conf)
+{
+	int pc = pathconf(path, conf);
+
+	return (pc < LUXIO_MIN_PATHSIZE) ? LUXIO_MIN_PATHSIZE : pc;
+}
+
+static int safe_fpathconf(int fd, int conf)
+{
+	int pc = fpathconf(fd, conf);
+
+	return (pc < LUXIO_MIN_PATHSIZE) ? LUXIO_MIN_PATHSIZE : pc;
+}
+
+#undef LUXIO_MIN_PATHSIZE
+
 /* External interface to Lua *************************************************/
 
 int luaopen_luxio(lua_State *L);
@@ -783,7 +803,7 @@ luxio_opendir(lua_State *L) /* 5.1.2 */
 	 * Hutchings' function mentioned in his article "readdir_r considered
 	 * harmful".
 	 */
-	bufz = sizeof(struct dirent) + pathconf(path, _PC_NAME_MAX) + 256;
+	bufz = sizeof(struct dirent) + safe_pathconf(path, _PC_NAME_MAX) + 256;
 	s->buf = malloc(bufz);
 
 	luxio__bless_readdir(L);
@@ -819,7 +839,7 @@ luxio_fdopendir(lua_State *L) /* POSIX.1-2008 */
 	 * Hutchings' function mentioned in his article "readdir_r considered
 	 * harmful".
 	 */
-	bufz = sizeof(struct dirent) + fpathconf(fd, _PC_NAME_MAX) + 256;
+	bufz = sizeof(struct dirent) + safe_fpathconf(fd, _PC_NAME_MAX) + 256;
 	s->buf = malloc(bufz);
 
 	luxio__bless_readdir(L);
@@ -938,7 +958,7 @@ luxio_chdir(lua_State *L) /* 5.2.1 */
 static int
 luxio_getcwd(lua_State *L) /* 5.2.2 */
 {
-	size_t buflen = pathconf("/", _PC_PATH_MAX) + 256;
+	size_t buflen = safe_pathconf("/", _PC_PATH_MAX) + 256;
 	char buf[buflen];
 
 	if (getcwd(buf, buflen) == NULL) {
@@ -1049,7 +1069,7 @@ luxio_symlink(lua_State *L) /* POSIX.1-2001, Unknown location */
 static int
 luxio_readlink(lua_State *L) /* POSIX.1-2001, Unknown location */
 {
-	size_t buflen = pathconf("/", _PC_PATH_MAX) + 256;
+	size_t buflen = safe_pathconf("/", _PC_PATH_MAX) + 256;
 	char buffer[buflen];
 	ssize_t ret;
 	const char *path = luaL_checkstring(L, 1);
@@ -1076,7 +1096,7 @@ luxio_mkstemp(lua_State *L)
 {
 	size_t infname_len;
 	const char *infname = luaL_optlstring(L, 1, "lux_XXXXXX", &infname_len);
-	size_t buflen = pathconf(infname, _PC_PATH_MAX) + 256;
+	size_t buflen = safe_pathconf(infname, _PC_PATH_MAX) + 256;
 	char fnamebuf[buflen];
 	int fd, saved_errno;