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Message-ID: <4A77F049.4050301@rs.jp.nec.com>
Date: Tue, 04 Aug 2009 17:24:41 +0900
From: Akira Fujita <a-fujita@...jp.nec.com>
To: Peng Tao <bergwolf@...il.com>
CC: linux-ext4@...r.kernel.org, "Theodore Ts'o" <tytso@....edu>
Subject: Re: [PATCH 2/2] ext4: fix null pointer bug in move_extent.c
Hi Peng,
Peng Tao wrote:
> Will there be situations where empty extents exist in the middle of an
> extent tree? Because your patch only checks NULL extents once at the
> begining. If some NULL extents are later found in the loop, the bug
> still can be triggered and we should check NULL extents in
> mext_replace_branches().
In the case of eh->entries is 0 in ext4_ext_find_extent(),
the extent which ext4_ext_path indicates is null.
This is happened if file blocks are not allocated yet.
But an extent tree does not have empty extents in the middle of it, I think.
I have no idea we should handle empty extents case in EXT4_IOC_MOVE_EXTENTS,
but if yes, we should do null check at other places
not only mext_replace_branches().
So I add this null check to get_ext_path macro
which is used to get ext4_ext_path.
Regards,
Akira Fujita
Signed-off-by: Akira Fujita <a-fujita@...jp.nec.com>
---
move_extent.c | 32 +++++++++++++++-----------------
1 file changed, 15 insertions(+), 17 deletions(-)
--- linux-2.6.31-rc4-a/fs/ext4/move_extent.c 2009-07-23 11:32:59.000000000 +0900
+++ linux-2.6.31-rc4-b/fs/ext4/move_extent.c 2009-08-04 15:51:04.000000000 +0900
@@ -25,6 +25,8 @@
if (IS_ERR(path)) { \
ret = PTR_ERR(path); \
path = NULL; \
+ } else if (path[ext_depth(inode)].p_ext == NULL) { \
+ ret = -ENOENT; \
} \
} while (0)
@@ -284,7 +286,7 @@ mext_insert_across_blocks(handle_t *hand
if (new_flag) {
get_ext_path(orig_path, orig_inode, eblock, err);
- if (orig_path == NULL)
+ if (err)
goto out;
if (ext4_ext_insert_extent(handle, orig_inode,
@@ -295,7 +297,7 @@ mext_insert_across_blocks(handle_t *hand
if (end_flag) {
get_ext_path(orig_path, orig_inode,
le32_to_cpu(end_ext->ee_block) - 1, err);
- if (orig_path == NULL)
+ if (err)
goto out;
if (ext4_ext_insert_extent(handle, orig_inode,
@@ -632,12 +634,12 @@ mext_replace_branches(handle_t *handle,
/* Get the original extent for the block "orig_off" */
get_ext_path(orig_path, orig_inode, orig_off, err);
- if (orig_path == NULL)
+ if (err)
goto out;
/* Get the donor extent for the head */
get_ext_path(donor_path, donor_inode, donor_off, err);
- if (donor_path == NULL)
+ if (err)
goto out;
depth = ext_depth(orig_inode);
oext = orig_path[depth].p_ext;
@@ -679,7 +681,7 @@ mext_replace_branches(handle_t *handle,
if (orig_path)
ext4_ext_drop_refs(orig_path);
get_ext_path(orig_path, orig_inode, orig_off, err);
- if (orig_path == NULL)
+ if (err)
goto out;
depth = ext_depth(orig_inode);
oext = orig_path[depth].p_ext;
@@ -694,7 +696,7 @@ mext_replace_branches(handle_t *handle,
ext4_ext_drop_refs(donor_path);
get_ext_path(donor_path, donor_inode,
donor_off, err);
- if (donor_path == NULL)
+ if (err)
goto out;
depth = ext_depth(donor_inode);
dext = donor_path[depth].p_ext;
@@ -1138,7 +1140,7 @@ ext4_move_extents(struct file *o_filp, s
donor_start, &len, *moved_len);
mext_double_up_read(orig_inode, donor_inode);
if (ret)
- goto out2;
+ goto out;
file_end = (i_size_read(orig_inode) - 1) >> orig_inode->i_blkbits;
block_end = block_start + len - 1;
@@ -1146,20 +1148,16 @@ ext4_move_extents(struct file *o_filp, s
len -= block_end - file_end;
get_ext_path(orig_path, orig_inode, block_start, ret);
- if (orig_path == NULL)
- goto out2;
+ if (ret)
+ goto out;
/* Get path structure to check the hole */
get_ext_path(holecheck_path, orig_inode, block_start, ret);
- if (holecheck_path == NULL)
+ if (ret)
goto out;
depth = ext_depth(orig_inode);
ext_cur = holecheck_path[depth].p_ext;
- if (ext_cur == NULL) {
- ret = -EINVAL;
- goto out;
- }
/*
* Get proper extent whose ee_block is beyond block_start
@@ -1282,7 +1280,7 @@ ext4_move_extents(struct file *o_filp, s
ext4_ext_drop_refs(holecheck_path);
get_ext_path(holecheck_path, orig_inode,
seq_start, ret);
- if (holecheck_path == NULL)
+ if (ret)
break;
depth = holecheck_path->p_depth;
@@ -1290,7 +1288,7 @@ ext4_move_extents(struct file *o_filp, s
if (orig_path)
ext4_ext_drop_refs(orig_path);
get_ext_path(orig_path, orig_inode, seq_start, ret);
- if (orig_path == NULL)
+ if (ret)
break;
ext_cur = holecheck_path[depth].p_ext;
@@ -1307,7 +1305,7 @@ out:
ext4_ext_drop_refs(holecheck_path);
kfree(holecheck_path);
}
-out2:
+
mext_inode_double_unlock(orig_inode, donor_inode);
if (ret)
--
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