From: Dan Carpenter <dan.carpenter@oracle.com>
To: "Theodore Ts'o" <tytso@mit.edu>
Cc: Andreas Dilger <adilger.kernel@dilger.ca>,
linux-ext4@vger.kernel.org, kernel-janitors@vger.kernel.org,
Yongqiang Yang <xiaoqiangnk@gmail.com>
Subject: [RFC] ext4: off by one check in ext4_ext_convert_to_initialized()
Date: Sat, 23 Jun 2012 12:15:20 +0300 [thread overview]
Message-ID: <20120623091520.GB26923@elgon.mountain> (raw)
I am not very familiar with this code, but I think that we should be
using "<= EXT4_EXT_ZERO_LEN" here instead of "< EXT4_EXT_ZERO_LEN".
1) The other comparisons with EXT4_EXT_ZERO_LEN use "<=".
2) On the first side of the if else statement we do:
if (allocated <= EXT4_EXT_ZERO_LEN ...
split_map.m_len = allocated;
On this side, it would match to do:
if (map->m_lblk - ee_block + map->m_len <= EXT4_EXT_ZERO_LEN ...
split_map.m_len = map->m_lblk - ee_block + map->m_len;
It's not the most air tight of arguments, so I've submitted this with a
big warning message.
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 91341ec..2df32a4 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -3208,7 +3208,7 @@ static int ext4_ext_convert_to_initialized(handle_t *handle,
goto out;
split_map.m_lblk = map->m_lblk;
split_map.m_len = allocated;
- } else if ((map->m_lblk - ee_block + map->m_len <
+ } else if ((map->m_lblk - ee_block + map->m_len <=
EXT4_EXT_ZERO_LEN) &&
(EXT4_EXT_MAY_ZEROOUT & split_flag)) {
/* case 2 */
reply other threads:[~2012-06-23 9:15 UTC|newest]
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