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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 <tytso@mit.edu>
Cc: stable@kernel.org
This commit is contained in:
Theodore Ts'o 2018-06-14 00:58:00 -04:00
parent 77260807d1
commit 8844618d8a
4 changed files with 36 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

11
fs/ext4/balloc.c
View File

@ -438,7 +438,16 @@ 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)) {
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);

14
fs/ext4/ialloc.c
View File

@ -150,7 +150,16 @@ 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");
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);
@ -994,7 +1003,8 @@ 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));

6
fs/ext4/mballoc.c
View File

@ -2444,7 +2444,8 @@ 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 {
@ -3010,7 +3011,8 @@ 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,

11
fs/ext4/super.c
View File

@ -3139,13 +3139,22 @@ 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;