ovl: fix regression in parsing of mount options with escaped comma

Ever since commit 91c77947133f ("ovl: allow filenames with comma"), the
following example was legit overlayfs mount options:

  mount -t overlay overlay -o 'lowerdir=/tmp/a\,b/lower' /mnt

The conversion to new mount api moved to using the common helper
generic_parse_monolithic() and discarded the specialized ovl_next_opt()
option separator.

Bring back ovl_next_opt() and use vfs_parse_monolithic_sep() to fix the
regression.

Reported-by: Ryan Hendrickson <ryan.hendrickson@alum.mit.edu>
Closes: https://lore.kernel.org/r/8da307fb-9318-cf78-8a27-ba5c5a0aef6d@alum.mit.edu/
Fixes: 1784fbc2ed9c ("ovl: port to new mount api")
Signed-off-by: Amir Goldstein <amir73il@gmail.com>

diff --git a/fs/overlayfs/params.c b/fs/overlayfs/params.c
index 95b7515..17c74ef 100644 (file)
--- a/fs/overlayfs/params.c
+++ b/fs/overlayfs/params.c
@@ -157,6 +157,34 @@ const struct fs_parameter_spec ovl_parameter_spec[] = {
        {}
 };
 
+static char *ovl_next_opt(char **s)
+{
+       char *sbegin = *s;
+       char *p;
+
+       if (sbegin == NULL)
+               return NULL;
+
+       for (p = sbegin; *p; p++) {
+               if (*p == '\\') {
+                       p++;
+                       if (!*p)
+                               break;
+               } else if (*p == ',') {
+                       *p = '\0';
+                       *s = p + 1;
+                       return sbegin;
+               }
+       }
+       *s = NULL;
+       return sbegin;
+}
+
+static int ovl_parse_monolithic(struct fs_context *fc, void *data)
+{
+       return vfs_parse_monolithic_sep(fc, data, ovl_next_opt);
+}
+
 static ssize_t ovl_parse_param_split_lowerdirs(char *str)
 {
        ssize_t nr_layers = 1, nr_colons = 0;
@@ -682,6 +710,7 @@ static int ovl_reconfigure(struct fs_context *fc)
 }
 
 static const struct fs_context_operations ovl_context_ops = {
+       .parse_monolithic = ovl_parse_monolithic,
        .parse_param = ovl_parse_param,
        .get_tree    = ovl_get_tree,
        .reconfigure = ovl_reconfigure,