Bug 199181
| Summary: | Out-of-bound access in ext4_valid_block_bitmap when mounting and operating on a crafted ext4 image | ||
|---|---|---|---|
| Product: | File System | Reporter: | Wen Xu (wen.xu) |
| Component: | ext4 | Assignee: | fs_ext4 (fs_ext4) |
| Status: | RESOLVED CODE_FIX | ||
| Severity: | normal | CC: | tytso, wen.xu |
| Priority: | P1 | ||
| Hardware: | All | ||
| OS: | Linux | ||
| Kernel Version: | 4.15.x | Subsystem: | |
| Regression: | No | Bisected commit-id: | |
| Attachments: |
The crafted image which causes kernel panic
poc.c |
||
|
Description
Wen Xu
2018-03-22 20:29:12 UTC
Created attachment 274879 [details]
poc.c
By the way, the dump is generated on latest Ubuntu 18.04 which uses Linux 4.15. Thanks for the bug report. The following should address the problem you have reported. commit 25584a8748b1f5404abcdc87c9fac21681eec5d2 Author: Theodore Ts'o <tytso@mit.edu> Date: Sat Mar 24 01:48:34 2018 -0400 ext4: add validity checks for bitmap block numbers https://bugzilla.kernel.org/show_bug.cgi?id=199181 Reported-by: Wen Xu <wen.xu@gatech.edu> Signed-off-by: Theodore Ts'o <tytso@mit.edu> Cc: stable@vger.kernel.org diff --git a/fs/ext4/balloc.c b/fs/ext4/balloc.c index f82c4966f4ce..a33d8fb1bf2a 100644 --- a/fs/ext4/balloc.c +++ b/fs/ext4/balloc.c @@ -338,20 +338,25 @@ static ext4_fsblk_t ext4_valid_block_bitmap(struct super_block *sb, /* 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 + sbi->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 super_block *sb, ext4_group_t block_group) 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 - " diff --git a/fs/ext4/ialloc.c b/fs/ext4/ialloc.c index 3fa93665b4a3..df92e3ec9913 100644 --- 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_block *sb, ext4_group_t block_group) 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 - " |