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    Subject[PATCH 4.14 077/164] ext4: add validity checks for bitmap block numbers
    Date
    4.14-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Theodore Ts'o <tytso@mit.edu>

    commit 7dac4a1726a9c64a517d595c40e95e2d0d135f6f upstream.

    An privileged attacker can cause a crash by mounting a crafted ext4
    image which triggers a out-of-bounds read in the function
    ext4_valid_block_bitmap() in fs/ext4/balloc.c.

    This issue has been assigned CVE-2018-1093.

    BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=199181
    BugLink: https://bugzilla.redhat.com/show_bug.cgi?id=1560782
    Reported-by: Wen Xu <wen.xu@gatech.edu>
    Signed-off-by: Theodore Ts'o <tytso@mit.edu>
    Cc: stable@vger.kernel.org
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    fs/ext4/balloc.c | 16 ++++++++++++++--
    fs/ext4/ialloc.c | 7 +++++++
    2 files changed, 21 insertions(+), 2 deletions(-)

    --- a/fs/ext4/balloc.c
    +++ b/fs/ext4/balloc.c
    @@ -338,20 +338,25 @@ static ext4_fsblk_t ext4_valid_block_bit
    /* check whether block bitmap block number is set */
    blk = ext4_block_bitmap(sb, desc);
    offset = blk - group_first_block;
    - if (!ext4_test_bit(EXT4_B2C(sbi, offset), bh->b_data))
    + if (offset < 0 || EXT4_B2C(sbi, offset) >= sb->s_blocksize ||
    + !ext4_test_bit(EXT4_B2C(sbi, offset), bh->b_data))
    /* bad block bitmap */
    return blk;

    /* check whether the inode bitmap block number is set */
    blk = ext4_inode_bitmap(sb, desc);
    offset = blk - group_first_block;
    - if (!ext4_test_bit(EXT4_B2C(sbi, offset), bh->b_data))
    + if (offset < 0 || EXT4_B2C(sbi, offset) >= sb->s_blocksize ||
    + !ext4_test_bit(EXT4_B2C(sbi, offset), bh->b_data))
    /* bad block bitmap */
    return blk;

    /* check whether the inode table block number is set */
    blk = ext4_inode_table(sb, desc);
    offset = blk - group_first_block;
    + if (offset < 0 || EXT4_B2C(sbi, offset) >= sb->s_blocksize ||
    + EXT4_B2C(sbi, offset + sbi->s_itb_per_group) >= sb->s_blocksize)
    + return blk;
    next_zero_bit = ext4_find_next_zero_bit(bh->b_data,
    EXT4_B2C(sbi, offset + EXT4_SB(sb)->s_itb_per_group),
    EXT4_B2C(sbi, offset));
    @@ -417,6 +422,7 @@ struct buffer_head *
    ext4_read_block_bitmap_nowait(struct super_block *sb, ext4_group_t block_group)
    {
    struct ext4_group_desc *desc;
    + struct ext4_sb_info *sbi = EXT4_SB(sb);
    struct buffer_head *bh;
    ext4_fsblk_t bitmap_blk;
    int err;
    @@ -425,6 +431,12 @@ ext4_read_block_bitmap_nowait(struct sup
    if (!desc)
    return ERR_PTR(-EFSCORRUPTED);
    bitmap_blk = ext4_block_bitmap(sb, desc);
    + if ((bitmap_blk <= le32_to_cpu(sbi->s_es->s_first_data_block)) ||
    + (bitmap_blk >= ext4_blocks_count(sbi->s_es))) {
    + ext4_error(sb, "Invalid block bitmap block %llu in "
    + "block_group %u", bitmap_blk, block_group);
    + return ERR_PTR(-EFSCORRUPTED);
    + }
    bh = sb_getblk(sb, bitmap_blk);
    if (unlikely(!bh)) {
    ext4_error(sb, "Cannot get buffer for block bitmap - "
    --- a/fs/ext4/ialloc.c
    +++ b/fs/ext4/ialloc.c
    @@ -122,6 +122,7 @@ static struct buffer_head *
    ext4_read_inode_bitmap(struct super_block *sb, ext4_group_t block_group)
    {
    struct ext4_group_desc *desc;
    + struct ext4_sb_info *sbi = EXT4_SB(sb);
    struct buffer_head *bh = NULL;
    ext4_fsblk_t bitmap_blk;
    int err;
    @@ -131,6 +132,12 @@ ext4_read_inode_bitmap(struct super_bloc
    return ERR_PTR(-EFSCORRUPTED);

    bitmap_blk = ext4_inode_bitmap(sb, desc);
    + if ((bitmap_blk <= le32_to_cpu(sbi->s_es->s_first_data_block)) ||
    + (bitmap_blk >= ext4_blocks_count(sbi->s_es))) {
    + ext4_error(sb, "Invalid inode bitmap blk %llu in "
    + "block_group %u", bitmap_blk, block_group);
    + return ERR_PTR(-EFSCORRUPTED);
    + }
    bh = sb_getblk(sb, bitmap_blk);
    if (unlikely(!bh)) {
    ext4_error(sb, "Cannot read inode bitmap - "

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