lkml.org 
[lkml]   [2022]   [Aug]   [23]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH 4.19 188/287] ext4: make sure ext4_append() always allocates new block
    Date
    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
    @@ -53,6 +53,7 @@ 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;

    @@ -62,6 +63,21 @@ 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))

    \
     
     \ /
      Last update: 2022-08-23 12:49    [W:4.048 / U:0.392 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site