4.9-stable review patch. If anyone has any objections, please let me know.
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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 @@ -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)) /* 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 - "