linux-ext4 - [PATCH] ext4: Avoid stamping on other memories in ext4_ext_insert

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Date:	Fri, 30 Sep 2011 17:35:04 +0800
From:	Tao Ma <tm@....ma>
To:	linux-ext4@...r.kernel.org
Cc:	"Theodore Ts'o" <tytso@....edu>
Subject: [PATCH] ext4: Avoid stamping on other memories in ext4_ext_insert_index.

From: Tao Ma <boyu.mt@...bao.com>

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. So move the check
before we do the work.

Cc: "Theodore Ts'o" <tytso@....edu>
Signed-off-by: Tao Ma <boyu.mt@...bao.com>
---
 fs/ext4/extents.c |    8 ++++----
 1 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 57cf568..37a1b4d 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -776,15 +776,15 @@ 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);
 
-- 
1.7.1

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