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 <sanbai@taobao.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index b8acfab..9bec432 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -741,6 +741,16 @@
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 */
@@ -770,14 +780,6 @@
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;