ext4: Make the extent validity check more paranoid
Instead of just checking that the extent block number is greater or
equal than s_first_data_block, make sure it it is not pointing into
the block group descriptors, since that is clearly wrong. This helps
prevent filesystem from getting very badly corrupted in case an extent
block is corrupted.
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 6132353..c28ffe2 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -326,11 +326,14 @@
static int ext4_valid_extent(struct inode *inode, struct ext4_extent *ext)
{
- ext4_fsblk_t block = ext_pblock(ext);
+ ext4_fsblk_t block = ext_pblock(ext), valid_block;
int len = ext4_ext_get_actual_len(ext);
struct ext4_super_block *es = EXT4_SB(inode->i_sb)->s_es;
- if (unlikely(block < le32_to_cpu(es->s_first_data_block) ||
- ((block + len) > ext4_blocks_count(es))))
+
+ valid_block = le32_to_cpu(es->s_first_data_block) +
+ EXT4_SB(inode->i_sb)->s_gdb_count;
+ if (unlikely(block <= valid_block ||
+ ((block + len) > ext4_blocks_count(es))))
return 0;
else
return 1;
@@ -339,10 +342,13 @@
static int ext4_valid_extent_idx(struct inode *inode,
struct ext4_extent_idx *ext_idx)
{
- ext4_fsblk_t block = idx_pblock(ext_idx);
+ ext4_fsblk_t block = idx_pblock(ext_idx), valid_block;
struct ext4_super_block *es = EXT4_SB(inode->i_sb)->s_es;
- if (unlikely(block < le32_to_cpu(es->s_first_data_block) ||
- (block >= ext4_blocks_count(es))))
+
+ valid_block = le32_to_cpu(es->s_first_data_block) +
+ EXT4_SB(inode->i_sb)->s_gdb_count;
+ if (unlikely(block <= valid_block ||
+ (block >= ext4_blocks_count(es))))
return 0;
else
return 1;