ufs: validate maximum fast symlink size from superblock

The maximum fast symlink size is set in the superblock of certain types
of UFS filesystem. Before using it we need to check that it isn't longer
than the available space we have in the inode.

Signed-off-by: Duane Griffin <duaneg@dghda.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 11 insertions, 0 deletions

diff --git a/fs/ufs/super.c b/fs/ufs/super.c
index 261a1c2f22dd..e1c1fc5ee239 100644
--- a/fs/ufs/super.c
+++ b/fs/ufs/super.c
@@ -636,6 +636,7 @@ static int ufs_fill_super(struct super_block *sb, void *data, int silent)
         unsigned block_size, super_block_size;
         unsigned flags;
         unsigned super_block_offset;
+        unsigned maxsymlen;
         int ret = -EINVAL;
 
         uspi = NULL;
@@ -1069,6 +1070,16 @@ magic_found:
                 uspi->s_maxsymlinklen =
                     fs32_to_cpu(sb, usb3->fs_un2.fs_44.fs_maxsymlinklen);
 
+        if (uspi->fs_magic == UFS2_MAGIC)
+                maxsymlen = 2 * 4 * (UFS_NDADDR + UFS_NINDIR);
+        else
+                maxsymlen = 4 * (UFS_NDADDR + UFS_NINDIR);
+        if (uspi->s_maxsymlinklen > maxsymlen) {
+                ufs_warning(sb, __func__, "ufs_read_super: excessive maximum "
+                            "fast symlink size (%u)\n", uspi->s_maxsymlinklen);
+                uspi->s_maxsymlinklen = maxsymlen;
+        }
+
         inode = ufs_iget(sb, UFS_ROOTINO);
         if (IS_ERR(inode)) {
                 ret = PTR_ERR(inode);