From: Theodore Ts'o Date: Thu, 14 Jun 2018 04:58:00 +0000 (-0400) Subject: ext4: only look at the bg_flags field if it is valid X-Git-Tag: v4.1.12-124.31.3~254 X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=ca706e54e1a2c884716d2954ce17ffa438a45af7;p=users%2Fjedix%2Flinux-maple.git ext4: only look at the bg_flags field if it is valid 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 Cc: stable@kernel.org (cherry picked from commit 8844618d8aa7a9973e7b527d038a2a589665002c) Orabug: 29316684 CVE: CVE-2018-10876. Signed-off-by: John Donnelly Reviewed-by: Allen Pais Signed-off-by: Brian Maly Conflicts: fs/ext4/balloc.c fs/ext4/ialloc.c Signed-off-by: Brian Maly --- diff --git a/fs/ext4/balloc.c b/fs/ext4/balloc.c index 9f08f2a8e87e..b0fdb9b19596 100644 --- a/fs/ext4/balloc.c +++ b/fs/ext4/balloc.c @@ -420,6 +420,7 @@ ext4_read_block_bitmap_nowait(struct super_block *sb, ext4_group_t block_group) struct ext4_sb_info *sbi = EXT4_SB(sb); struct buffer_head *bh; ext4_fsblk_t bitmap_blk; + int err; desc = ext4_get_group_desc(sb, block_group, NULL); if (!desc) @@ -448,9 +449,16 @@ 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)) { - int err; - + 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); @@ -483,6 +491,7 @@ verify: ext4_validate_block_bitmap(sb, desc, block_group, bh); if (buffer_verified(bh)) return bh; +out: put_bh(bh); return NULL; } diff --git a/fs/ext4/ialloc.c b/fs/ext4/ialloc.c index 3cb8be756e23..d0afdae08cb7 100644 --- a/fs/ext4/ialloc.c +++ b/fs/ext4/ialloc.c @@ -126,6 +126,7 @@ ext4_read_inode_bitmap(struct super_block *sb, ext4_group_t block_group) ext4_fsblk_t bitmap_blk; struct ext4_group_info *grp; struct ext4_sb_info *sbi = EXT4_SB(sb); + int err = 0; desc = ext4_get_group_desc(sb, block_group, NULL); if (!desc) @@ -155,8 +156,19 @@ 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)) { - ext4_init_inode_bitmap(sb, bh, block_group, desc); + 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); set_bitmap_uptodate(bh); set_buffer_uptodate(bh); set_buffer_verified(bh); @@ -213,6 +225,9 @@ verify: ext4_unlock_group(sb, block_group); set_buffer_verified(bh); return bh; +out: + put_bh(bh); + return ERR_PTR(err); } /* @@ -909,7 +924,8 @@ 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 0eba2331ca47..a9cdaef7938c 100644 --- a/fs/ext4/mballoc.c +++ b/fs/ext4/mballoc.c @@ -2411,7 +2411,8 @@ 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 { @@ -2935,7 +2936,8 @@ 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 e3e45120fb39..3589eae580d8 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -3160,13 +3160,22 @@ 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_rdonly(sb)) + return ngroups; } return group;