ovl: fix regression in showing lowerdir mount option

Before commit b36a5780cb44 ("ovl: modify layer parameter parsing"),
spaces and commas in lowerdir mount option value used to be escaped using
seq_show_option().

In current upstream, when lowerdir value has a space, it is not escaped
in /proc/mounts, e.g.:

  none /mnt overlay rw,relatime,lowerdir=l l,upperdir=u,workdir=w 0 0

which results in broken output of the mount utility:

  none on /mnt type overlay (rw,relatime,lowerdir=l)

Store the original lowerdir mount options before unescaping and show
them using the same escaping used for seq_show_option() in addition to
escaping the colon separator character.

Fixes: b36a5780cb44 ("ovl: modify layer parameter parsing")
Signed-off-by: Amir Goldstein <amir73il@gmail.com>

diff --git a/Documentation/filesystems/overlayfs.rst b/Documentation/filesystems/overlayfs.rst
index cdefbe73d85c8a04261839a287badac3253b47cb..5b93268e400f4c78e3adf20210574cc840aa6b96 100644 (file)
--- a/Documentation/filesystems/overlayfs.rst
+++ b/Documentation/filesystems/overlayfs.rst
@@ -339,6 +339,18 @@ The specified lower directories will be stacked beginning from the
 rightmost one and going left.  In the above example lower1 will be the
 top, lower2 the middle and lower3 the bottom layer.
 
+Note: directory names containing colons can be provided as lower layer by
+escaping the colons with a single backslash.  For example:
+
+  mount -t overlay overlay -olowerdir=/a\:lower\:\:dir /merged
+
+Since kernel version v6.5, directory names containing colons can also
+be provided as lower layer using the fsconfig syscall from new mount api:
+
+  fsconfig(fs_fd, FSCONFIG_SET_STRING, "lowerdir", "/a:lower::dir", 0);
+
+In the latter case, colons in lower layer directory names will be escaped
+as an octal characters (\072) when displayed in /proc/self/mountinfo.
 
 Metadata only copy up
 ---------------------

diff --git a/fs/overlayfs/params.c b/fs/overlayfs/params.c
index 17c74ef4f089b9e61d78e87d40715632b6ba963b..8b6bae320e8a26b9f4b7ec66fb5ebefb43e64ed7 100644 (file)
--- a/fs/overlayfs/params.c
+++ b/fs/overlayfs/params.c
@@ -192,7 +192,8 @@ static ssize_t ovl_parse_param_split_lowerdirs(char *str)
 
        for (s = d = str;; s++, d++) {
                if (*s == '\\') {
-                       s++;
+                       /* keep esc chars in split lowerdir */
+                       *d++ = *s++;
                } else if (*s == ':') {
                        bool next_colon = (*(s + 1) == ':');
 
@@ -267,7 +268,7 @@ static void ovl_unescape(char *s)
        }
 }
 
-static int ovl_mount_dir(const char *name, struct path *path)
+static int ovl_mount_dir(const char *name, struct path *path, bool upper)
 {
        int err = -ENOMEM;
        char *tmp = kstrdup(name, GFP_KERNEL);
@@ -276,7 +277,7 @@ static int ovl_mount_dir(const char *name, struct path *path)
                ovl_unescape(tmp);
                err = ovl_mount_dir_noesc(tmp, path);
 
-               if (!err && path->dentry->d_flags & DCACHE_OP_REAL) {
+               if (!err && upper && path->dentry->d_flags & DCACHE_OP_REAL) {
                        pr_err("filesystem on '%s' not supported as upperdir\n",
                               tmp);
                        path_put_init(path);
@@ -297,7 +298,7 @@ static int ovl_parse_param_upperdir(const char *name, struct fs_context *fc,
        struct path path;
        char *dup;
 
-       err = ovl_mount_dir(name, &path);
+       err = ovl_mount_dir(name, &path, true);
        if (err)
                return err;
 
@@ -500,7 +501,7 @@ static int ovl_parse_param_lowerdir(const char *name, struct fs_context *fc)
                l = &ctx->lower[nr];
                memset(l, 0, sizeof(*l));
 
-               err = ovl_mount_dir_noesc(dup_iter, &l->path);
+               err = ovl_mount_dir(dup_iter, &l->path, false);
                if (err)
                        goto out_put;
 
@@ -979,16 +980,23 @@ int ovl_show_options(struct seq_file *m, struct dentry *dentry)
        struct super_block *sb = dentry->d_sb;
        struct ovl_fs *ofs = OVL_FS(sb);
        size_t nr, nr_merged_lower = ofs->numlayer - ofs->numdatalayer;
-       char **lowerdatadirs = &ofs->config.lowerdirs[nr_merged_lower];
-
-       /* lowerdirs[] starts from offset 1 */
-       seq_printf(m, ",lowerdir=%s", ofs->config.lowerdirs[1]);
-       /* dump regular lower layers */
-       for (nr = 2; nr < nr_merged_lower; nr++)
-               seq_printf(m, ":%s", ofs->config.lowerdirs[nr]);
-       /* dump data lower layers */
-       for (nr = 0; nr < ofs->numdatalayer; nr++)
-               seq_printf(m, "::%s", lowerdatadirs[nr]);
+
+       /*
+        * lowerdirs[] starts from offset 1, then
+        * >= 0 regular lower layers prefixed with : and
+        * >= 0 data-only lower layers prefixed with ::
+        *
+        * we need to escase comma and space like seq_show_option() does and
+        * we also need to escape the colon separator from lowerdir paths.
+        */
+       seq_puts(m, ",lowerdir=");
+       for (nr = 1; nr < ofs->numlayer; nr++) {
+               if (nr > 1)
+                       seq_putc(m, ':');
+               if (nr >= nr_merged_lower)
+                       seq_putc(m, ':');
+               seq_escape(m, ofs->config.lowerdirs[nr], ":, \t\n\\");
+       }
        if (ofs->config.upperdir) {
                seq_show_option(m, "upperdir", ofs->config.upperdir);
                seq_show_option(m, "workdir", ofs->config.workdir);