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    Subject[PATCH 5.15 748/779] ext4: check if directory block is within i_size
    Date
    From: Lukas Czerner <lczerner@redhat.com>

    [ Upstream commit 65f8ea4cd57dbd46ea13b41dc8bac03176b04233 ]

    Currently ext4 directory handling code implicitly assumes that the
    directory blocks are always within the i_size. In fact ext4_append()
    will attempt to allocate next directory block based solely on i_size and
    the i_size is then appropriately increased after a successful
    allocation.

    However, for this to work it requires i_size to be correct. If, for any
    reason, the directory inode i_size is corrupted in a way that the
    directory tree refers to a valid directory block past i_size, we could
    end up corrupting parts of the directory tree structure by overwriting
    already used directory blocks when modifying the directory.

    Fix it by catching the corruption early in __ext4_read_dirblock().

    Addresses Red-Hat-Bugzilla: #2070205
    CVE: CVE-2022-1184
    Signed-off-by: Lukas Czerner <lczerner@redhat.com>
    Cc: stable@vger.kernel.org
    Reviewed-by: Andreas Dilger <adilger@dilger.ca>
    Link: https://lore.kernel.org/r/20220704142721.157985-1-lczerner@redhat.com
    Signed-off-by: Theodore Ts'o <tytso@mit.edu>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    fs/ext4/namei.c | 7 +++++++
    1 file changed, 7 insertions(+)

    diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
    index 871eebf12bf4..ac0b7e53591f 100644
    --- a/fs/ext4/namei.c
    +++ b/fs/ext4/namei.c
    @@ -110,6 +110,13 @@ static struct buffer_head *__ext4_read_dirblock(struct inode *inode,
    struct ext4_dir_entry *dirent;
    int is_dx_block = 0;

    + if (block >= inode->i_size) {
    + ext4_error_inode(inode, func, line, block,
    + "Attempting to read directory block (%u) that is past i_size (%llu)",
    + block, inode->i_size);
    + return ERR_PTR(-EFSCORRUPTED);
    + }
    +
    if (ext4_simulate_fail(inode->i_sb, EXT4_SIM_DIRBLOCK_EIO))
    bh = ERR_PTR(-EIO);
    else
    --
    2.35.1


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