From: Tao Ma <boyu.mt@taobao.com>
Date: Sat, 8 Oct 2011 21:18:27 +0000 (-0400)
Subject: ext4: avoid stamping on other memories in ext4_ext_insert_index()
X-Git-Tag: next-20111011~83^2~3
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=4fd30c0330ba951d579ee3f0c24eaf1fa0580719;p=karo-tx-linux.git

ext4: avoid stamping on other memories in ext4_ext_insert_index()

In ext4_ext_insert_index, we initialize 'ix' before checking its
validity, so we have a chance to stamp on memories out of the block.
Move the check before we do the work.

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

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index f473ddf0bd94..2dff31efa33e 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -779,15 +779,15 @@ static int ext4_ext_insert_index(handle_t *handle, struct inode *inode,
 		ix = curp->p_idx;
 	}
 
-	ix->ei_block = cpu_to_le32(logical);
-	ext4_idx_store_pblock(ix, ptr);
-	le16_add_cpu(&curp->p_hdr->eh_entries, 1);
-
 	if (unlikely(ix > EXT_LAST_INDEX(curp->p_hdr))) {
 		EXT4_ERROR_INODE(inode, "ix > EXT_LAST_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);
+
 	err = ext4_ext_dirty(handle, inode, curp);
 	ext4_std_error(inode->i_sb, err);