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| author | Theodore Ts'o <tytso@mit.edu> | 2018-03-27 06:54:10 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2018-05-02 17:59:53 +0300 |
| commit | 0643dbdb5c697fbe20dd380bcb3faa1dcec03b78 (patch) | |
| tree | 59123144000f9a2e83ad517eea0ac12089e1ed2e /fs/ext4/balloc.c | |
| parent | d0800f61b95703d09607217ad4d5775c5313429b (diff) | |
| download | linux-0643dbdb5c697fbe20dd380bcb3faa1dcec03b78.tar.xz | |
ext4: add validity checks for bitmap block numbers
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.
Backport notes:
3.18.y is missing commit 6a797d273783 ("ext4: call out CRC and corruption errors with specific error codes")
so the EFSCORRUPTED label doesn't exist. Replaced
all instances of EFSCORRUPTED with EUCLEAN since that's
what 6a797d273783 defined it as.
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
[harsh@prjkt.io: s/EFSCORRUPTED/EUCLEAN/ fs/ext4/balloc.c]
Signed-off-by: Harsh Shandilya <harsh@prjkt.io>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'fs/ext4/balloc.c')
| -rw-r--r-- | fs/ext4/balloc.c | 16 |
1 files changed, 14 insertions, 2 deletions
diff --git a/fs/ext4/balloc.c b/fs/ext4/balloc.c index 0a46c50f1bdc..cbc1c40818f5 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 + EXT4_SB(sb)->s_itb_per_group), EXT4_B2C(sbi, offset)); @@ -414,6 +419,7 @@ 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; @@ -421,6 +427,12 @@ ext4_read_block_bitmap_nowait(struct super_block *sb, ext4_group_t block_group) if (!desc) return NULL; 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(-EUCLEAN); + } bh = sb_getblk(sb, bitmap_blk); if (unlikely(!bh)) { ext4_error(sb, "Cannot get buffer for block bitmap - " |