4.9-stable review patch. If anyone has any objections, please let me know. ------------------ From: Theodore Ts'o <tytso@xxxxxxx> commit 8844618d8aa7a9973e7b527d038a2a589665002c upstream. The bg_flags field in the block group descripts is only valid if the uninit_bg or metadata_csum feature is enabled. We were not consistently looking at this field; fix this. Also block group #0 must never have uninitialized allocation bitmaps, or need to be zeroed, since that's where the root inode, and other special inodes are set up. Check for these conditions and mark the file system as corrupted if they are detected. This addresses CVE-2018-10876. https://bugzilla.kernel.org/show_bug.cgi?id=199403 Signed-off-by: Theodore Ts'o <tytso@xxxxxxx> Cc: stable@xxxxxxxxxx Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- fs/ext4/balloc.c | 11 ++++++++++- fs/ext4/ialloc.c | 14 ++++++++++++-- fs/ext4/mballoc.c | 6 ++++-- fs/ext4/super.c | 11 ++++++++++- 4 files changed, 36 insertions(+), 6 deletions(-) --- a/fs/ext4/balloc.c +++ b/fs/ext4/balloc.c @@ -450,7 +450,16 @@ ext4_read_block_bitmap_nowait(struct sup goto verify; } ext4_lock_group(sb, block_group); - if (desc->bg_flags & cpu_to_le16(EXT4_BG_BLOCK_UNINIT)) { + if (ext4_has_group_desc_csum(sb) && + (desc->bg_flags & cpu_to_le16(EXT4_BG_BLOCK_UNINIT))) { + if (block_group == 0) { + ext4_unlock_group(sb, block_group); + unlock_buffer(bh); + ext4_error(sb, "Block bitmap for bg 0 marked " + "uninitialized"); + err = -EFSCORRUPTED; + goto out; + } err = ext4_init_block_bitmap(sb, bh, block_group, desc); set_bitmap_uptodate(bh); set_buffer_uptodate(bh); --- a/fs/ext4/ialloc.c +++ b/fs/ext4/ialloc.c @@ -152,7 +152,16 @@ ext4_read_inode_bitmap(struct super_bloc } ext4_lock_group(sb, block_group); - if (desc->bg_flags & cpu_to_le16(EXT4_BG_INODE_UNINIT)) { + if (ext4_has_group_desc_csum(sb) && + (desc->bg_flags & cpu_to_le16(EXT4_BG_INODE_UNINIT))) { + if (block_group == 0) { + ext4_unlock_group(sb, block_group); + unlock_buffer(bh); + ext4_error(sb, "Inode bitmap for bg 0 marked " + "uninitialized"); + err = -EFSCORRUPTED; + goto out; + } memset(bh->b_data, 0, (EXT4_INODES_PER_GROUP(sb) + 7) / 8); ext4_mark_bitmap_end(EXT4_INODES_PER_GROUP(sb), sb->s_blocksize * 8, bh->b_data); @@ -926,7 +935,8 @@ got: /* recheck and clear flag under lock if we still need to */ ext4_lock_group(sb, group); - if (gdp->bg_flags & cpu_to_le16(EXT4_BG_BLOCK_UNINIT)) { + if (ext4_has_group_desc_csum(sb) && + (gdp->bg_flags & cpu_to_le16(EXT4_BG_BLOCK_UNINIT))) { gdp->bg_flags &= cpu_to_le16(~EXT4_BG_BLOCK_UNINIT); ext4_free_group_clusters_set(sb, gdp, ext4_free_clusters_after_init(sb, group, gdp)); --- a/fs/ext4/mballoc.c +++ b/fs/ext4/mballoc.c @@ -2444,7 +2444,8 @@ int ext4_mb_add_groupinfo(struct super_b * initialize bb_free to be able to skip * empty groups without initialization */ - if (desc->bg_flags & cpu_to_le16(EXT4_BG_BLOCK_UNINIT)) { + if (ext4_has_group_desc_csum(sb) && + (desc->bg_flags & cpu_to_le16(EXT4_BG_BLOCK_UNINIT))) { meta_group_info[i]->bb_free = ext4_free_clusters_after_init(sb, group, desc); } else { @@ -2969,7 +2970,8 @@ ext4_mb_mark_diskspace_used(struct ext4_ #endif ext4_set_bits(bitmap_bh->b_data, ac->ac_b_ex.fe_start, ac->ac_b_ex.fe_len); - if (gdp->bg_flags & cpu_to_le16(EXT4_BG_BLOCK_UNINIT)) { + if (ext4_has_group_desc_csum(sb) && + (gdp->bg_flags & cpu_to_le16(EXT4_BG_BLOCK_UNINIT))) { gdp->bg_flags &= cpu_to_le16(~EXT4_BG_BLOCK_UNINIT); ext4_free_group_clusters_set(sb, gdp, ext4_free_clusters_after_init(sb, --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -3023,13 +3023,22 @@ static ext4_group_t ext4_has_uninit_itab ext4_group_t group, ngroups = EXT4_SB(sb)->s_groups_count; struct ext4_group_desc *gdp = NULL; + if (!ext4_has_group_desc_csum(sb)) + return ngroups; + for (group = 0; group < ngroups; group++) { gdp = ext4_get_group_desc(sb, group, NULL); if (!gdp) continue; - if (!(gdp->bg_flags & cpu_to_le16(EXT4_BG_INODE_ZEROED))) + if (gdp->bg_flags & cpu_to_le16(EXT4_BG_INODE_ZEROED)) + continue; + if (group != 0) break; + ext4_error(sb, "Inode table for bg 0 marked as " + "needing zeroing"); + if (sb->s_flags & MS_RDONLY) + return ngroups; } return group;
