On Sun, 2018-04-22 at 15:53 +0200, Greg Kroah-Hartman wrote: > 4.9-stable review patch. If anyone has any objections, please let me know. > > ------------------ > > From: Theodore Ts'o <[email protected]> > > 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 <[email protected]> > Signed-off-by: Theodore Ts'o <[email protected]> > Cc: [email protected] > Signed-off-by: Greg Kroah-Hartman <[email protected]> > > --- > 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 > @@ -337,20 +337,25 @@ 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))
Isn't sb->s_blocksize a count of bytes? If so, doesn't that mean that
we should be comparing with sb->s_blocksize * 8?
Ben.
> /* 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));
> @@ -416,6 +421,7 @@ 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;
> @@ -424,6 +430,12 @@ 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
> @@ -119,6 +119,7 @@ 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;
> @@ -128,6 +129,12 @@ 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 - "
>
>
--
Ben Hutchings
It is easier to write an incorrect program
than to understand a correct one.
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