ext4: avoid stamping on other memories in ext4_ext_insert_index()

Add a sanity check to make sure ix hasn't gone beyond the valid bounds
of the extent block.

Signed-off-by: Tao Ma <boyu.mt@taobao.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

1 files changed, 5 insertions, 0 deletions

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index f473ddf0bd94..5c4861210d4c 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -779,6 +779,11 @@ static int ext4_ext_insert_index(handle_t *handle, struct inode *inode,
                 ix = curp->p_idx;
         }
 
+        if (unlikely(ix > EXT_MAX_INDEX(curp->p_hdr))) {
+                EXT4_ERROR_INODE(inode, "ix > EXT_MAX_INDEX!");
+                return -EIO;
+        }
+
         ix->ei_block = cpu_to_le32(logical);
         ext4_idx_store_pblock(ix, ptr);
         le16_add_cpu(&curp->p_hdr->eh_entries, 1);