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ext4: make sure ext4_append() always allocates new block 

ext4_append() must always allocate a new block, otherwise we run the
risk of overwriting existing directory block corrupting the directory
tree in the process resulting in all manner of problems later on.

Add a sanity check to see if the logical block is already allocated and
error out if it is.

Cc: stable@kernel.org
Signed-off-by: Lukas Czerner <lczerner@redhat.com>
Reviewed-by: Andreas Dilger <adilger@dilger.ca>
Link: https://lore.kernel.org/r/20220704142721.157985-2-lczerner@redhat.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
This commit is contained in:
Lukas Czerner 2022-07-04 16:27:21 +02:00 committed by Theodore Ts'o
parent 65f8ea4cd5
commit b8a04fe77e
1 changed files with 16 additions and 0 deletions
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16
fs/ext4/namei.c
View File

@ -54,6 +54,7 @@ static struct buffer_head *ext4_append(handle_t *handle,
struct inode *inode,
ext4_lblk_t *block)
{
struct ext4_map_blocks map;
struct buffer_head *bh;
int err;
@ -63,6 +64,21 @@ static struct buffer_head *ext4_append(handle_t *handle,
return ERR_PTR(-ENOSPC);
*block = inode->i_size >> inode->i_sb->s_blocksize_bits;
map.m_lblk = *block;
map.m_len = 1;
/*
* We're appending new directory block. Make sure the block is not
* allocated yet, otherwise we will end up corrupting the
* directory.
*/
err = ext4_map_blocks(NULL, inode, &map, 0);
if (err < 0)
return ERR_PTR(err);
if (err) {
EXT4_ERROR_INODE(inode, "Logical block already allocated");
return ERR_PTR(-EFSCORRUPTED);
}
bh = ext4_bread(handle, inode, *block, EXT4_GET_BLOCKS_CREATE);
if (IS_ERR(bh))