ext4: add validity checks for bitmap block numbers
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
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@ -338,20 +338,25 @@ static ext4_fsblk_t ext4_valid_block_bitmap(struct super_block *sb,
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/* check whether block bitmap block number is set */
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blk = ext4_block_bitmap(sb, desc);
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offset = blk - group_first_block;
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if (!ext4_test_bit(EXT4_B2C(sbi, offset), bh->b_data))
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if (offset < 0 || EXT4_B2C(sbi, offset) >= sb->s_blocksize ||
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!ext4_test_bit(EXT4_B2C(sbi, offset), bh->b_data))
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/* bad block bitmap */
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return blk;
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/* check whether the inode bitmap block number is set */
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blk = ext4_inode_bitmap(sb, desc);
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offset = blk - group_first_block;
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if (!ext4_test_bit(EXT4_B2C(sbi, offset), bh->b_data))
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if (offset < 0 || EXT4_B2C(sbi, offset) >= sb->s_blocksize ||
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!ext4_test_bit(EXT4_B2C(sbi, offset), bh->b_data))
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/* bad block bitmap */
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return blk;
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/* check whether the inode table block number is set */
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blk = ext4_inode_table(sb, desc);
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offset = blk - group_first_block;
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if (offset < 0 || EXT4_B2C(sbi, offset) >= sb->s_blocksize ||
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EXT4_B2C(sbi, offset + sbi->s_itb_per_group) >= sb->s_blocksize)
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return blk;
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next_zero_bit = ext4_find_next_zero_bit(bh->b_data,
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EXT4_B2C(sbi, offset + sbi->s_itb_per_group),
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EXT4_B2C(sbi, offset));
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@ -417,6 +422,7 @@ struct buffer_head *
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ext4_read_block_bitmap_nowait(struct super_block *sb, ext4_group_t block_group)
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{
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struct ext4_group_desc *desc;
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struct ext4_sb_info *sbi = EXT4_SB(sb);
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struct buffer_head *bh;
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ext4_fsblk_t bitmap_blk;
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int err;
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@ -425,6 +431,12 @@ ext4_read_block_bitmap_nowait(struct super_block *sb, ext4_group_t block_group)
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if (!desc)
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return ERR_PTR(-EFSCORRUPTED);
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bitmap_blk = ext4_block_bitmap(sb, desc);
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if ((bitmap_blk <= le32_to_cpu(sbi->s_es->s_first_data_block)) ||
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(bitmap_blk >= ext4_blocks_count(sbi->s_es))) {
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ext4_error(sb, "Invalid block bitmap block %llu in "
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"block_group %u", bitmap_blk, block_group);
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return ERR_PTR(-EFSCORRUPTED);
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}
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bh = sb_getblk(sb, bitmap_blk);
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if (unlikely(!bh)) {
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ext4_error(sb, "Cannot get buffer for block bitmap - "
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@ -122,6 +122,7 @@ static struct buffer_head *
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ext4_read_inode_bitmap(struct super_block *sb, ext4_group_t block_group)
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{
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struct ext4_group_desc *desc;
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struct ext4_sb_info *sbi = EXT4_SB(sb);
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struct buffer_head *bh = NULL;
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ext4_fsblk_t bitmap_blk;
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int err;
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@ -131,6 +132,12 @@ ext4_read_inode_bitmap(struct super_block *sb, ext4_group_t block_group)
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return ERR_PTR(-EFSCORRUPTED);
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bitmap_blk = ext4_inode_bitmap(sb, desc);
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if ((bitmap_blk <= le32_to_cpu(sbi->s_es->s_first_data_block)) ||
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(bitmap_blk >= ext4_blocks_count(sbi->s_es))) {
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ext4_error(sb, "Invalid inode bitmap blk %llu in "
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"block_group %u", bitmap_blk, block_group);
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return ERR_PTR(-EFSCORRUPTED);
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}
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bh = sb_getblk(sb, bitmap_blk);
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if (unlikely(!bh)) {
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ext4_error(sb, "Cannot read inode bitmap - "
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