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Message-ID: <1267741715.13886.4.camel@michlmayr>
Date: Thu, 04 Mar 2010 23:28:35 +0100
From: Leonard Michlmayr <leonard.michlmayr@...il.com>
To: Akira Fujita <a-fujita@...jp.nec.com>, tytso@....edu
Cc: Ext4 Developers List <linux-ext4@...r.kernel.org>
Subject: [incomplete PATCH] ext4: avoid overflow in fiemap
A __u32 cannot hold the maximum number of blocks in a file. This may
lead to an overflow if a fiemap request has length = s_maxbytes.
I still get a segfault, I have to go through it again. This is just for
your information. I will work on it tomorrow.
The patch is to be applied after/at the end of the ext4 patch queue.
Appearently only fiemap uses ext4_ext_walk_space(). Therefore I changed
the semantics of the ext4_ext_walk_space() call. I hope this does not
introduce a new problem.
In the case that 1<<32 blocks are requested, but there are no allocated
extents, I return two gaps because, the length of a gap in the
ext4_ext_cache is a __u32 again.
Regards
Leonard
Signed-off-by: Leonard Michlmayr <leonard.michlmayr@...il.com>
diff -puar linux-2.6.33-ted/fs/ext4/extents.c linux-2.6.33-lm/fs/ext4/extents.c
--- linux-2.6.33-ted/fs/ext4/extents.c 2010-03-04 21:08:00.000000000 +0100
+++ linux-2.6.33-lm/fs/ext4/extents.c 2010-03-04 22:50:54.000000000 +0100
@@ -1853,21 +1853,21 @@ cleanup:
}
int ext4_ext_walk_space(struct inode *inode, ext4_lblk_t block,
- ext4_lblk_t num, ext_prepare_callback func,
+ ext4_lblk_t last, ext_prepare_callback func,
void *cbdata)
{
struct ext4_ext_path *path = NULL;
struct ext4_ext_cache cbex;
struct ext4_extent *ex;
ext4_lblk_t next, start = 0, end = 0;
- ext4_lblk_t last = block + num;
int depth, exists, err = 0;
BUG_ON(func == NULL);
BUG_ON(inode == NULL);
- while (block < last && block != EXT_MAX_BLOCK) {
- num = last - block;
+ while (block <= last && block != EXT_MAX_BLOCK) {
+ /* num is one less than the number of blocks */
+ ext4_lblk_t num = last - block;
/* find extent for this block */
down_read(&EXT4_I(inode)->i_data_sem);
path = ext4_ext_find_extent(inode, block, path);
@@ -1893,10 +1893,12 @@ int ext4_ext_walk_space(struct inode *in
* all requested space */
start = block;
end = block + num;
+ if (end - start >= EXT_MAX_BLOCK)
+ end = EXT_MAX_BLOCK - 1;
} else if (le32_to_cpu(ex->ee_block) > block) {
/* need to allocate space before found extent */
start = block;
- end = le32_to_cpu(ex->ee_block);
+ end = le32_to_cpu(ex->ee_block) - 1;
if (block + num < end)
end = block + num;
} else if (block >= le32_to_cpu(ex->ee_block)
@@ -1904,8 +1906,11 @@ int ext4_ext_walk_space(struct inode *in
/* need to allocate space after found extent */
start = block;
end = block + num;
+ if (end - start >= EXT_MAX_BLOCK)
+ end = EXT_MAX_BLOCK - 1;
+ BUG_ON(next == 0);
if (end >= next)
- end = next;
+ end = next - 1;
} else if (block >= le32_to_cpu(ex->ee_block)) {
/*
* some part of requested space is covered
@@ -1913,7 +1918,7 @@ int ext4_ext_walk_space(struct inode *in
*/
start = block;
end = le32_to_cpu(ex->ee_block)
- + ext4_ext_get_actual_len(ex);
+ + (ext4_ext_get_actual_len(ex) - 1);
if (block + num < end)
end = block + num;
exists = 1;
@@ -1924,7 +1929,7 @@ int ext4_ext_walk_space(struct inode *in
if (!exists) {
cbex.ec_block = start;
- cbex.ec_len = end - start;
+ cbex.ec_len = end - start + 1;
cbex.ec_start = 0;
cbex.ec_type = EXT4_EXT_CACHE_GAP;
} else {
@@ -3894,7 +3899,6 @@ static int ext4_xattr_fiemap(struct inod
int ext4_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
__u64 start, __u64 len)
{
- ext4_lblk_t start_blk;
int error = 0;
/* fallback to generic here if not in extents fmt */
@@ -3908,17 +3912,16 @@ int ext4_fiemap(struct inode *inode, str
if (fieinfo->fi_flags & FIEMAP_FLAG_XATTR) {
error = ext4_xattr_fiemap(inode, fieinfo);
} else {
- ext4_lblk_t last_blk, len_blks;
+ ext4_lblk_t start_blk, last_blk;
start_blk = start >> inode->i_sb->s_blocksize_bits;
- last_blk = (start + len - 1) >> inode->i_sb->s_blocksize_bits;
- len_blks = last_blk - start_blk + 1;
+ last_blk = (len - 1 + start) >> inode->i_sb->s_blocksize_bits;
/*
* Walk the extent tree gathering extent information.
* ext4_ext_fiemap_cb will push extents back to user.
*/
- error = ext4_ext_walk_space(inode, start_blk, len_blks,
+ error = ext4_ext_walk_space(inode, start_blk, last_blk,
ext4_ext_fiemap_cb, fieinfo);
}
--
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