xfs: sanitize remount options

Perform basic sanitization of remount options by
passing the option string and a dummy mount structure
through xfs_parseargs and returning the result.

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
index 9e1538d48548b52a99449cb463534d9064aff957..8dd7d165902d18a2e6312e31f97a111659594a60 100644 (file)
--- a/fs/xfs/xfs_super.c
+++ b/fs/xfs/xfs_super.c
@@ -172,13 +172,17 @@ suffix_kstrtoint(const substring_t *s, unsigned int base, int *res)
  *
  * Note that this function leaks the various device name allocations on
  * failure.  The caller takes care of them.
+ *
+ * *sb is const because this is also used to test options on the remount
+ * path, and we don't want this to have any side effects at remount time.
+ * Today this function does not change *sb, but just to future-proof...
  */
 STATIC int
 xfs_parseargs(
        struct xfs_mount        *mp,
        char                    *options)
 {
-       struct super_block      *sb = mp->m_super;
+       const struct super_block *sb = mp->m_super;
        char                    *p;
        substring_t             args[MAX_OPT_ARGS];
        int                     dsunit = 0;
@@ -1169,6 +1173,27 @@ xfs_quiesce_attr(
        xfs_log_quiesce(mp);
 }
 
+STATIC int
+xfs_test_remount_options(
+       struct super_block      *sb,
+       struct xfs_mount        *mp,
+       char                    *options)
+{
+       int                     error = 0;
+       struct xfs_mount        *tmp_mp;
+
+       tmp_mp = kmem_zalloc(sizeof(*tmp_mp), KM_MAYFAIL);
+       if (!tmp_mp)
+               return -ENOMEM;
+
+       tmp_mp->m_super = sb;
+       error = xfs_parseargs(tmp_mp, options);
+       xfs_free_fsname(tmp_mp);
+       kfree(tmp_mp);
+
+       return error;
+}
+
 STATIC int
 xfs_fs_remount(
        struct super_block      *sb,
@@ -1181,6 +1206,11 @@ xfs_fs_remount(
        char                    *p;
        int                     error;
 
+       /* First, check for complete junk; i.e. invalid options */
+       error = xfs_test_remount_options(sb, mp, options);
+       if (error)
+               return error;
+
        sync_filesystem(sb);
        while ((p = strsep(&options, ",")) != NULL) {
                int token;