cgroups: fix memory leak and simplify code

src/lxc/cgroups/cgfsng.c

@@ -54,19 +54,6 @@
 
 lxc_log_define(cgfsng, cgroup);
 
-static void free_string_list(char **clist)
-{
-	int i;
-
-	if (!clist)
-		return;
-
-	for (i = 0; clist[i]; i++)
-		free(clist[i]);
-
-	free(clist);
-}
-
 /* Given a pointer to a null-terminated array of pointers, realloc to add one
  * entry, and point the new entry to NULL. Do not fail. Return the index to the
  * second-to-last entry - that is, the one which is now available for use
@@ -2940,12 +2927,11 @@ static void cg_unified_delegate(char ***delegate)
  */
 static int cg_hybrid_init(struct cgroup_ops *ops, bool relative, bool unprivileged)
 {
-	__do_free char *basecginfo = NULL;
-	__do_free char *line = NULL;
+	__do_free char *basecginfo = NULL, *line = NULL;
+	__do_free_string_list char **klist = NULL, **nlist = NULL;
 	__do_fclose FILE *f = NULL;
 	int ret;
 	size_t len = 0;
-	char **klist = NULL, **nlist = NULL;
 
 	/* Root spawned containers escape the current cgroup, so use init's
 	 * cgroups as our base in that case.
@@ -2968,11 +2954,11 @@ static int cg_hybrid_init(struct cgroup_ops *ops, bool relative, bool unprivileg
 	lxc_cgfsng_print_basecg_debuginfo(basecginfo, klist, nlist);
 
 	while (getline(&line, &len, f) != -1) {
+		__do_free char *base_cgroup = NULL, *mountpoint = NULL;
+		__do_free_string_list char **controller_list = NULL;
 		int type;
 		bool writeable;
 		struct hierarchy *new;
-		char *base_cgroup = NULL, *mountpoint = NULL;
-		char **controller_list = NULL;
 
 		type = get_cgroup_version(line);
 		if (type == 0)
@@ -3000,18 +2986,18 @@ static int cg_hybrid_init(struct cgroup_ops *ops, bool relative, bool unprivileg
 
 		if (type == CGROUP_SUPER_MAGIC)
 			if (controller_list_is_dup(ops->hierarchies, controller_list))
-				log_trace_errno(goto next, EEXIST, "Skipping duplicating controller");
+				log_trace_errno(continue, EEXIST, "Skipping duplicating controller");
 
 		mountpoint = cg_hybrid_get_mountpoint(line);
 		if (!mountpoint)
-			log_error_errno(goto next, EINVAL, "Failed parsing mountpoint from \"%s\"", line);
+			log_error_errno(continue, EINVAL, "Failed parsing mountpoint from \"%s\"", line);
 
 		if (type == CGROUP_SUPER_MAGIC)
 			base_cgroup = cg_hybrid_get_current_cgroup(basecginfo, controller_list[0], CGROUP_SUPER_MAGIC);
 		else
 			base_cgroup = cg_hybrid_get_current_cgroup(basecginfo, NULL, CGROUP2_SUPER_MAGIC);
 		if (!base_cgroup)
-			log_error_errno(goto next, EINVAL, "Failed to find current cgroup");
+			log_error_errno(continue, EINVAL, "Failed to find current cgroup");
 
 		trim(base_cgroup);
 		prune_init_scope(base_cgroup);
@@ -3020,7 +3006,7 @@ static int cg_hybrid_init(struct cgroup_ops *ops, bool relative, bool unprivileg
 		else
 			writeable = test_writeable_v1(mountpoint, base_cgroup);
 		if (!writeable)
-			log_trace_errno(goto next, EROFS, "The %s group is not writeable", base_cgroup);
+			log_trace_errno(continue, EROFS, "The %s group is not writeable", base_cgroup);
 
 		if (type == CGROUP2_SUPER_MAGIC) {
 			char *cgv2_ctrl_path;
@@ -3040,26 +3026,16 @@ static int cg_hybrid_init(struct cgroup_ops *ops, bool relative, bool unprivileg
 
 		/* Exclude all controllers that cgroup use does not want. */
 		if (!cgroup_use_wants_controllers(ops, controller_list))
-			log_trace_errno(goto next, EINVAL, "Skipping controller");
+			log_trace_errno(continue, EINVAL, "Skipping controller");
 
-		new = add_hierarchy(&ops->hierarchies, controller_list, mountpoint, base_cgroup, type);
+		new = add_hierarchy(&ops->hierarchies, move_ptr(controller_list), move_ptr(mountpoint), move_ptr(base_cgroup), type);
 		if (type == CGROUP2_SUPER_MAGIC && !ops->unified) {
 			if (unprivileged)
 				cg_unified_delegate(&new->cgroup2_chown);
 			ops->unified = new;
 		}
-
-		continue;
-
-	next:
-		free_string_list(controller_list);
-		free(mountpoint);
-		free(base_cgroup);
 	}
 
-	free_string_list(klist);
-	free_string_list(nlist);
-
 	TRACE("Writable cgroup hierarchies:");
 	lxc_cgfsng_print_hierarchies(ops);
 

src/lxc/memory_utils.h

@@ -13,11 +13,35 @@
 
 #include "macro.h"
 
+#define define_cleanup_attribute(type, func)     \
+	static inline void func##_ptr(type *ptr) \
+	{                                        \
+		if (*ptr)                        \
+			func(*ptr);              \
+	}
+
+#define free_disarm(ptr)       \
+	({                     \
+		free(ptr);     \
+		move_ptr(ptr); \
+	})
+
 static inline void __auto_free__(void *p)
 {
 	free(*(void **)p);
 }
 
+static inline void free_string_list(char **list)
+{
+	if (list) {
+		for (int i = 0; list[i]; i++)
+			free(list[i]);
+		free_disarm(list);
+	}
+}
+define_cleanup_attribute(char **, free_string_list);
+#define __do_free_string_list __attribute__((__cleanup__(free_string_list_ptr)))
+
 static inline void __auto_fclose__(FILE **f)
 {
 	if (*f)
@@ -38,12 +62,6 @@ static inline void __auto_closedir__(DIR **d)
 		fd = -EBADF;        \
 	}
 
-#define free_disarm(ptr)       \
-	({                     \
-		free(ptr);     \
-		move_ptr(ptr); \
-	})
-
 static inline void __auto_close__(int *fd)
 {
 	close_prot_errno_disarm(*fd);

src/lxc/pam/pam_cgfs.c

@@ -77,7 +77,6 @@ static inline void clear_bit(unsigned bit, uint32_t *bitarr)
 	bitarr[bit / NBITS] &= ~(1 << (bit % NBITS));
 }
 static char *copy_to_eol(char *s);
-static void free_string_list(char **list);
 static char *get_mountpoint(char *line);
 static bool get_uid_gid(const char *user, uid_t *uid, gid_t *gid);
 static int handle_login(const char *user, uid_t uid, gid_t gid);
@@ -454,16 +453,6 @@ static size_t string_list_length(char **list)
 	return len;
 }
 
-/* Free null-terminated array of strings. */
-static void free_string_list(char **list)
-{
-	char **it;
-
-	for (it = list; it && *it; it++)
-		free(*it);
-	free(list);
-}
-
 /* Write single integer to file. */
 static bool write_int(char *path, int v)
 {