ext4: Fix different block exchange issue in EXT4_IOC_MOVE_EXT

If logical block offset of original file which is passed to
EXT4_IOC_MOVE_EXT is different from donor file's,
a calculation error occurs in ext4_calc_swap_extents(),
therefore wrong block is exchanged between original file and donor file.
As a result, we hit ext4_error() in check_block_validity().
To detect the logical offset difference in EXT4_IOC_MOVE_EXT,
add checks to mext_calc_swap_extents() and handle it as error,
since data exchange must be done between the same blocks in EXT4_IOC_MOVE_EXT.

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

1 files changed, 37 insertions, 9 deletions

diff --git a/fs/ext4/move_extent.c b/fs/ext4/move_extent.c
index 1c509d549137..1f027b1ec430 100644
--- a/fs/ext4/move_extent.c
+++ b/fs/ext4/move_extent.c
@@ -597,8 +597,10 @@ out:
  * @orig_off:           block offset of original inode
  * @donor_off:          block offset of donor inode
  * @max_count:          the maximun length of extents
+ *
+ * Return 0 on success, or a negative error value on failure.
  */
-static void
+static int
 mext_calc_swap_extents(struct ext4_extent *tmp_dext,
                               struct ext4_extent *tmp_oext,
                               ext4_lblk_t orig_off, ext4_lblk_t donor_off,
@@ -607,6 +609,19 @@ mext_calc_swap_extents(struct ext4_extent *tmp_dext,
         ext4_lblk_t diff, orig_diff;
         struct ext4_extent dext_old, oext_old;
 
+        BUG_ON(orig_off != donor_off);
+
+        /* original and donor extents have to cover the same block offset */
+        if (orig_off < le32_to_cpu(tmp_oext->ee_block) ||
+            le32_to_cpu(tmp_oext->ee_block) +
+                        ext4_ext_get_actual_len(tmp_oext) - 1 < orig_off)
+                return -ENODATA;
+
+        if (orig_off < le32_to_cpu(tmp_dext->ee_block) ||
+            le32_to_cpu(tmp_dext->ee_block) +
+                        ext4_ext_get_actual_len(tmp_dext) - 1 < orig_off)
+                return -ENODATA;
+
         dext_old = *tmp_dext;
         oext_old = *tmp_oext;
 
@@ -634,6 +649,8 @@ mext_calc_swap_extents(struct ext4_extent *tmp_dext,
 
         copy_extent_status(&oext_old, tmp_dext);
         copy_extent_status(&dext_old, tmp_oext);
+
+        return 0;
 }
 
 /**
@@ -690,8 +707,10 @@ mext_replace_branches(handle_t *handle, struct inode *orig_inode,
         dext = donor_path[depth].p_ext;
         tmp_dext = *dext;
 
-        mext_calc_swap_extents(&tmp_dext, &tmp_oext, orig_off,
+        err = mext_calc_swap_extents(&tmp_dext, &tmp_oext, orig_off,
                                       donor_off, count);
+        if (err)
+                goto out;
 
         /* Loop for the donor extents */
         while (1) {
@@ -760,9 +779,10 @@ mext_replace_branches(handle_t *handle, struct inode *orig_inode,
                 }
                 tmp_dext = *dext;
 
-                mext_calc_swap_extents(&tmp_dext, &tmp_oext, orig_off,
-                                              donor_off,
-                                              count - replaced_count);
+                err = mext_calc_swap_extents(&tmp_dext, &tmp_oext, orig_off,
+                                           donor_off, count - replaced_count);
+                if (err)
+                        goto out;
         }
 
 out:
@@ -1243,11 +1263,15 @@ ext4_move_extents(struct file *o_filp, struct file *d_filp,
         ext_cur = holecheck_path[depth].p_ext;
 
         /*
-         * Get proper extent whose ee_block is beyond block_start
-         * if block_start was within the hole.
+         * Get proper starting location of block replacement if block_start was
+         * within the hole.
          */
         if (le32_to_cpu(ext_cur->ee_block) +
                 ext4_ext_get_actual_len(ext_cur) - 1 < block_start) {
+                /*
+                 * The hole exists between extents or the tail of
+                 * original file.
+                 */
                 last_extent = mext_next_extent(orig_inode,
                                         holecheck_path, &ext_cur);
                 if (last_extent < 0) {
@@ -1260,8 +1284,12 @@ ext4_move_extents(struct file *o_filp, struct file *d_filp,
                         ret1 = last_extent;
                         goto out;
                 }
-        }
-        seq_start = block_start;
+                seq_start = le32_to_cpu(ext_cur->ee_block);
+        } else if (le32_to_cpu(ext_cur->ee_block) > block_start)
+                /* The hole exists at the beginning of original file. */
+                seq_start = le32_to_cpu(ext_cur->ee_block);
+        else
+                seq_start = block_start;
 
         /* No blocks within the specified range. */
         if (le32_to_cpu(ext_cur->ee_block) > block_end) {