diff --git a/src/cgroups/cgroup_utils.c b/src/cgroups/cgroup_utils.c
index 078f864..c21e7bc 100644
--- a/src/cgroups/cgroup_utils.c
+++ b/src/cgroups/cgroup_utils.c
@@ -521,23 +521,28 @@ static char *copy_to_eol(char *p)
 	return sret;
 }
 
-static void batch_realloc(char **mem, size_t oldlen, size_t newlen)
+char *batch_realloc(char *mem, size_t oldlen, size_t newlen)
 {
 	int newbatches = (newlen / BATCH_SIZE) + 1;
 	int oldbatches = (oldlen / BATCH_SIZE) + 1;
 
-	if (!*mem || newbatches > oldbatches) {
-		*mem = must_realloc(*mem, newbatches * BATCH_SIZE);
+	if (!mem || newbatches > oldbatches) {
+		char *tmp;
+		tmp = must_realloc(mem, newbatches * BATCH_SIZE);
+		return tmp;
 	}
+	return mem;
 }
 
-void append_line(char **dest, size_t oldlen, char *new, size_t newlen)
+char *append_line(char *dest, size_t oldlen, char *new, size_t newlen)
 {
+	char *tmp;
 	size_t full = oldlen + newlen;
 
-	batch_realloc(dest, oldlen, full + 1);
+	tmp = batch_realloc(dest, oldlen, full + 1);
 
-	memcpy(*dest + oldlen, new, newlen + 1);
+	memcpy(tmp + oldlen, new, newlen + 1);
+	return tmp;
 }
 
 static inline void drop_trailing_newlines(char *s)
@@ -561,7 +566,7 @@ char *read_file(const char *fnam)
 	if (!f)
 		return NULL;
 	while ((linelen = getline(&line, &len, f)) != -1) {
-		append_line(&buf, fulllen, line, linelen);
+		buf = append_line(buf, fulllen, line, linelen);
 		fulllen += linelen;
 	}
 	return buf;
@@ -691,7 +696,7 @@ char *readat_file(int dirfd, const char *path)
 	move_fd(fd);
 
 	while ((linelen = getline(&line, &len, f)) != -1) {
-		append_line(&buf, fulllen, line, linelen);
+		buf = append_line(buf, fulllen, line, linelen);
 		fulllen += linelen;
 	}
 
diff --git a/src/cgroups/cgroup_utils.h b/src/cgroups/cgroup_utils.h
index d1f5639..a40bdf5 100644
--- a/src/cgroups/cgroup_utils.h
+++ b/src/cgroups/cgroup_utils.h
@@ -79,7 +79,7 @@ extern size_t strlcat(char *d, const char *s, size_t n);
 #endif
 
 extern FILE *fopen_cloexec(const char *path, const char *mode);
-extern void append_line(char **dest, size_t oldlen, char *new, size_t newlen);
+extern char *append_line(char *dest, size_t oldlen, char *new, size_t newlen);
 extern char *read_file(const char *fnam);
 extern char *readat_file(int fd, const char *path);
 extern char *read_file_strip_newline(const char *fnam);
diff --git a/src/proc_fuse.c b/src/proc_fuse.c
index 6b503d6..334f6ea 100644
--- a/src/proc_fuse.c
+++ b/src/proc_fuse.c
@@ -1403,6 +1403,9 @@ __lxcfs_fuse_ops int proc_read(const char *path, char *buf, size_t size,
 {
 	struct file_info *f = INTTYPE_TO_PTR(fi->fh);
 
+	if (!f->buf)
+		return -EINVAL;
+
 	switch (f->type) {
 	case LXC_TYPE_PROC_MEMINFO:
 		if (liblxcfs_functional())