2011-06-27 06:29:49

by Robin Dong

Subject: [PATCH v3] ext4: avoid eh_entries overflow before insert extent_idx

If eh_entries is equal to (or greater than) eh_max, the operation of
inserting new extent_idx will make number of entries overflow.
So check eh_entries before inserting the new extent_idx.

Although there is no bug case according the code (function ext4_ext_insert_index
is called by ext4_ext_split and ext4_ext_split is called only if the index
block has free space), the right logic should be "lookup the capacity before
insertion".

Signed-off-by: Robin Dong <[email protected]>
---
fs/ext4/extents.c | 18 ++++++++++--------
1 files changed, 10 insertions(+), 8 deletions(-)

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index eb63c7b..792e77e 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -776,6 +776,16 @@ static int ext4_ext_insert_index(handle_t *handle, struct inode *inode,
logical, le32_to_cpu(curp->p_idx->ei_block));
return -EIO;
}
+
+ if (unlikely(le16_to_cpu(curp->p_hdr->eh_entries)
+ >= le16_to_cpu(curp->p_hdr->eh_max))) {
+ EXT4_ERROR_INODE(inode,
+ "eh_entries %d >= eh_max %d!",
+ le16_to_cpu(curp->p_hdr->eh_entries),
+ le16_to_cpu(curp->p_hdr->eh_max));
+ return -EIO;
+ }
+
len = EXT_MAX_INDEX(curp->p_hdr) - curp->p_idx;
if (logical > le32_to_cpu(curp->p_idx->ei_block)) {
/* insert after */
@@ -805,14 +815,6 @@ static int ext4_ext_insert_index(handle_t *handle, struct inode *inode,
ext4_idx_store_pblock(ix, ptr);
le16_add_cpu(&curp->p_hdr->eh_entries, 1);

- if (unlikely(le16_to_cpu(curp->p_hdr->eh_entries)
- > le16_to_cpu(curp->p_hdr->eh_max))) {
- EXT4_ERROR_INODE(inode,
- "eh_entries %d > eh_max %d!",
- le16_to_cpu(curp->p_hdr->eh_entries),
- le16_to_cpu(curp->p_hdr->eh_max));
- return -EIO;
- }
if (unlikely(ix > EXT_LAST_INDEX(curp->p_hdr))) {
EXT4_ERROR_INODE(inode, "ix > EXT_LAST_INDEX!");
return -EIO;
--
1.7.1

2011-07-18 03:46:29

by Theodore Ts'o

Subject: Re: [PATCH v3] ext4: avoid eh_entries overflow before insert extent_idx

On Mon, Jun 27, 2011 at 02:29:40PM +0800, Robin Dong wrote:
> If eh_entries is equal to (or greater than) eh_max, the operation of
> inserting new extent_idx will make number of entries overflow.
> So check eh_entries before inserting the new extent_idx.
>
> Although there is no bug case according the code (function ext4_ext_insert_index
> is called by ext4_ext_split and ext4_ext_split is called only if the index
> block has free space), the right logic should be "lookup the capacity before
> insertion".
>
> Signed-off-by: Robin Dong <[email protected]>

Thanks, added to the ext4 tree.

- Ted