From: Lukas Czerner lczerner@redhat.com
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: 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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/ext4/namei.c | 16 ++++++++++++++++ 1 file changed, 16 insertions(+)
--- a/fs/ext4/namei.c +++ b/fs/ext4/namei.c @@ -51,6 +51,7 @@ static struct buffer_head *ext4_append(h struct inode *inode, ext4_lblk_t *block) { + struct ext4_map_blocks map; struct buffer_head *bh; int err;
@@ -60,6 +61,21 @@ static struct buffer_head *ext4_append(h 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))