1 files changed, 22 insertions, 12 deletions

diff --git a/util-linux/mount.c b/util-linux/mount.c
index 3ac8ce093..0f213bb30 100644
--- a/util-linux/mount.c
+++ b/util-linux/mount.c
@@ -332,7 +332,7 @@ static void append_mount_options(char **oldopts, const char *newopts)
 }
 
 // Use the mount_options list to parse options into flags.
-// Also return list of unrecognized options if unrecognized != NULL
+// Also update list of unrecognized options if unrecognized != NULL
 static long parse_mount_options(char *options, char **unrecognized)
 {
         long flags = MS_SILENT;
@@ -348,25 +348,35 @@ static long parse_mount_options(char *options, char **unrecognized)
 // FIXME: use hasmntopt()
                 // Find this option in mount_options
                 for (i = 0; i < ARRAY_SIZE(mount_options); i++) {
-                        if (!strcasecmp(option_str, options)) {
+                        if (strcasecmp(option_str, options) == 0) {
                                 long fl = mount_options[i];
-                                if (fl < 0) flags &= fl;
-                                else flags |= fl;
-                                break;
+                                if (fl < 0)
+                                        flags &= fl;
+                                else
+                                        flags |= fl;
+                                goto found;
                         }
                         option_str += strlen(option_str) + 1;
                 }
-                // If unrecognized not NULL, append unrecognized mount options
-                if (unrecognized && i == ARRAY_SIZE(mount_options)) {
+                // We did not recognize this option.
+                // If "unrecognized" is not NULL, append option there.
+                // Note that we should not append *empty* option -
+                // in this case we want to pass NULL, not "", to "data"
+                // parameter of mount(2) syscall.
+                // This is crucial for filesystems that don't accept
+                // any arbitrary mount options, like cgroup fs:
+                // "mount -t cgroup none /mnt"
+                if (options[0] && unrecognized) {
                         // Add it to strflags, to pass on to kernel
-                        i = *unrecognized ? strlen(*unrecognized) : 0;
-                        *unrecognized = xrealloc(*unrecognized, i + strlen(options) + 2);
+                        char *p = *unrecognized;
+                        unsigned len = p ? strlen(p) : 0;
+                        *unrecognized = p = xrealloc(p, len + strlen(options) + 2);
 
                         // Comma separated if it's not the first one
-                        if (i) (*unrecognized)[i++] = ',';
-                        strcpy((*unrecognized)+i, options);
+                        if (len) p[len++] = ',';
+                        strcpy(p + len, options);
                 }
-
+ found:
                 if (!comma)
                         break;
                 // Advance to next option