ext4: Fix the NULL reference in double_down_write_data_sem()

If EXT4_IOC_MOVE_EXT ioctl is called with NULL donor_fd, fget() in
ext4_ioctl() gets inappropriate file structure for donor; so we need
to do this check earlier, before calling double_down_write_data_sem().

Signed-off-by: Akira Fujita <a-fujita@rs.jp.nec.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

diff --git a/fs/ext4/move_extent.c b/fs/ext4/move_extent.c
index 9eca1c0ec5460e04cb7de52854d0d5c38454d1a2..7e99f4e72bf5858c51991d95db3deb97b7bb158d 100644 (file)
--- a/fs/ext4/move_extent.c
+++ b/fs/ext4/move_extent.c
@@ -953,14 +953,6 @@ mext_check_arguments(struct inode *orig_inode,
        unsigned int blkbits = orig_inode->i_blkbits;
        unsigned int blocksize = 1 << blkbits;
 
-       /* Regular file check */
-       if (!S_ISREG(orig_inode->i_mode) || !S_ISREG(donor_inode->i_mode)) {
-               ext4_debug("ext4 move extent: The argument files should be "
-                       "regular file [ino:orig %lu, donor %lu]\n",
-                       orig_inode->i_ino, donor_inode->i_ino);
-               return -EINVAL;
-       }
-
        if (donor_inode->i_mode & (S_ISUID|S_ISGID)) {
                ext4_debug("ext4 move extent: suid or sgid is set"
                           " to donor file [ino:orig %lu, donor %lu]\n",
@@ -1208,6 +1200,14 @@ ext4_move_extents(struct file *o_filp, struct file *d_filp,
                return -EINVAL;
        }
 
+       /* Regular file check */
+       if (!S_ISREG(orig_inode->i_mode) || !S_ISREG(donor_inode->i_mode)) {
+               ext4_debug("ext4 move extent: The argument files should be "
+                       "regular file [ino:orig %lu, donor %lu]\n",
+                       orig_inode->i_ino, donor_inode->i_ino);
+               return -EINVAL;
+       }
+
        /* Protect orig and donor inodes against a truncate */
        ret1 = mext_inode_double_lock(orig_inode, donor_inode);
        if (ret1 < 0)