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> [bwh: Backported to 3.16: - ext4_read_block_bitmap_nowait() and ext4_read_inode_bitmap() return a pointer (NULL on error) instead of an error code - Open-code sb_rdonly() - Adjust context] Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx> [ghackmann@xxxxxxxxxx: forward-port to 3.18: adjust context] Signed-off-by: Greg Hackmann <ghackmann@xxxxxxxxxx> --- 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(-) diff --git a/fs/ext4/balloc.c b/fs/ext4/balloc.c index e19719ecff69..7b7691353cf3 100644 --- a/fs/ext4/balloc.c +++ b/fs/ext4/balloc.c @@ -451,9 +451,18 @@ ext4_read_block_bitmap_nowait(struct super_block *sb, ext4_group_t block_group) 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))) { int err; + if (block_group == 0) { + ext4_unlock_group(sb, block_group); + unlock_buffer(bh); + ext4_error(sb, "Block bitmap for bg 0 marked " + "uninitialized"); + put_bh(bh); + return NULL; + } err = ext4_init_block_bitmap(sb, bh, block_group, desc); set_bitmap_uptodate(bh); set_buffer_uptodate(bh); diff --git a/fs/ext4/ialloc.c b/fs/ext4/ialloc.c index 28aaf640745f..ab2b6f082633 100644 --- a/fs/ext4/ialloc.c +++ b/fs/ext4/ialloc.c @@ -117,7 +117,16 @@ ext4_read_inode_bitmap(struct super_block *sb, ext4_group_t block_group) } 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"); + put_bh(bh); + return NULL; + } 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); @@ -873,7 +882,8 @@ 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)); diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c index 6f51f016f80b..d8a729754e2c 100644 --- a/fs/ext4/mballoc.c +++ b/fs/ext4/mballoc.c @@ -2415,7 +2415,8 @@ int ext4_mb_add_groupinfo(struct super_block *sb, ext4_group_t group, * 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 { @@ -2942,7 +2943,8 @@ ext4_mb_mark_diskspace_used(struct ext4_allocation_context *ac, #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, diff --git a/fs/ext4/super.c b/fs/ext4/super.c index cd1fb8cf5161..6bff55db4d8f 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -3132,13 +3132,22 @@ static ext4_group_t ext4_has_uninit_itable(struct super_block *sb) 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; -- 2.19.0.605.g01d371f741-goog
