Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 41ff115b authored by Lukas Czerner's avatar Lukas Czerner Committed by Greg Kroah-Hartman
Browse files

ext4: make sure ext4_append() always allocates new block 



commit b8a04fe77ef1360fbf73c80fddbdfeaa9407ed1b upstream.

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: default avatarLukas Czerner <lczerner@redhat.com>
Reviewed-by: default avatarAndreas Dilger <adilger@dilger.ca>
Link: https://lore.kernel.org/r/20220704142721.157985-2-lczerner@redhat.com


Signed-off-by: default avatarTheodore Ts'o <tytso@mit.edu>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 748d17d4

fs/ext4/namei.c

+16 −0
Original line number Diff line number Diff line
@@ -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))