ext4: Add null extent check to ext_get_path

There is the possibility that path structure which is taken
by ext4_ext_find_extent() indicates null extents.
Because during data block exchanging in ext4_move_extents(),
constitution of an extent tree may be changed.
As a solution, the patch adds null extent check
to ext_get_path().

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, 16 insertions, 18 deletions

diff --git a/fs/ext4/move_extent.c b/fs/ext4/move_extent.c
index 2258560e9722..1c509d549137 100644
--- a/fs/ext4/move_extent.c
+++ b/fs/ext4/move_extent.c
@@ -39,7 +39,9 @@ get_ext_path(struct inode *inode, ext4_lblk_t lblock,
         if (IS_ERR(*path)) {
                 ret = PTR_ERR(*path);
                 *path = NULL;
-        }
+        } else if ((*path)[ext_depth(inode)].p_ext == NULL)
+                ret = -ENODATA;
+
         return ret;
 }
 
@@ -316,7 +318,7 @@ mext_insert_across_blocks(handle_t *handle, struct inode *orig_inode,
 
         if (new_flag) {
                 err = get_ext_path(orig_inode, eblock, &orig_path);
-                if (orig_path == NULL)
+                if (err)
                         goto out;
 
                 if (ext4_ext_insert_extent(handle, orig_inode,
@@ -327,7 +329,7 @@ mext_insert_across_blocks(handle_t *handle, struct inode *orig_inode,
         if (end_flag) {
                 err = get_ext_path(orig_inode,
                                 le32_to_cpu(end_ext->ee_block) - 1, &orig_path);
-                if (orig_path == NULL)
+                if (err)
                         goto out;
 
                 if (ext4_ext_insert_extent(handle, orig_inode,
@@ -673,12 +675,12 @@ mext_replace_branches(handle_t *handle, struct inode *orig_inode,
 
         /* Get the original extent for the block "orig_off" */
         err = get_ext_path(orig_inode, orig_off, &orig_path);
-        if (orig_path == NULL)
+        if (err)
                 goto out;
 
         /* Get the donor extent for the head */
         err = get_ext_path(donor_inode, donor_off, &donor_path);
-        if (donor_path == NULL)
+        if (err)
                 goto out;
         depth = ext_depth(orig_inode);
         oext = orig_path[depth].p_ext;
@@ -733,7 +735,7 @@ mext_replace_branches(handle_t *handle, struct inode *orig_inode,
                 if (orig_path)
                         ext4_ext_drop_refs(orig_path);
                 err = get_ext_path(orig_inode, orig_off, &orig_path);
-                if (orig_path == NULL)
+                if (err)
                         goto out;
                 depth = ext_depth(orig_inode);
                 oext = orig_path[depth].p_ext;
@@ -747,7 +749,7 @@ mext_replace_branches(handle_t *handle, struct inode *orig_inode,
                 if (donor_path)
                         ext4_ext_drop_refs(donor_path);
                 err = get_ext_path(donor_inode, donor_off, &donor_path);
-                if (donor_path == NULL)
+                if (err)
                         goto out;
                 depth = ext_depth(donor_inode);
                 dext = donor_path[depth].p_ext;
@@ -1221,7 +1223,7 @@ ext4_move_extents(struct file *o_filp, struct file *d_filp,
                                         donor_start, &len, *moved_len);
         mext_double_up_read(orig_inode, donor_inode);
         if (ret1)
-                goto out2;
+                goto out;
 
         file_end = (i_size_read(orig_inode) - 1) >> orig_inode->i_blkbits;
         block_end = block_start + len - 1;
@@ -1229,20 +1231,16 @@ ext4_move_extents(struct file *o_filp, struct file *d_filp,
                 len -= block_end - file_end;
 
         ret1 = get_ext_path(orig_inode, block_start, &orig_path);
-        if (orig_path == NULL)
-                goto out2;
+        if (ret1)
+                goto out;
 
         /* Get path structure to check the hole */
         ret1 = get_ext_path(orig_inode, block_start, &holecheck_path);
-        if (holecheck_path == NULL)
+        if (ret1)
                 goto out;
 
         depth = ext_depth(orig_inode);
         ext_cur = holecheck_path[depth].p_ext;
-        if (ext_cur == NULL) {
-                ret1 = -EINVAL;
-                goto out;
-        }
 
         /*
          * Get proper extent whose ee_block is beyond block_start
@@ -1371,7 +1369,7 @@ ext4_move_extents(struct file *o_filp, struct file *d_filp,
                 if (holecheck_path)
                         ext4_ext_drop_refs(holecheck_path);
                 ret1 = get_ext_path(orig_inode, seq_start, &holecheck_path);
-                if (holecheck_path == NULL)
+                if (ret1)
                         break;
                 depth = holecheck_path->p_depth;
 
@@ -1379,7 +1377,7 @@ ext4_move_extents(struct file *o_filp, struct file *d_filp,
                 if (orig_path)
                         ext4_ext_drop_refs(orig_path);
                 ret1 = get_ext_path(orig_inode, seq_start, &orig_path);
-                if (orig_path == NULL)
+                if (ret1)
                         break;
 
                 ext_cur = holecheck_path[depth].p_ext;
@@ -1396,7 +1394,7 @@ out:
                 ext4_ext_drop_refs(holecheck_path);
                 kfree(holecheck_path);
         }
-out2:
+
         ret2 = mext_inode_double_unlock(orig_inode, donor_inode);
 
         if (ret1)