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Date: Fri, 12 Oct 2018 13:56:16 +0200
Subject: [PATCH] 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.
Upstream-Status: Backport
https://bugzilla.kernel.org/show_bug.cgi?id=199403
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@kernel.org
Signed-off-by: Andreas Wellving <andreas.wellving@enea.com>
---
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 e04ec86..10e18f7 100644
--- a/fs/ext4/balloc.c
+++ b/fs/ext4/balloc.c
@@ -443,7 +443,16 @@ 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);
diff --git a/fs/ext4/ialloc.c b/fs/ext4/ialloc.c
index 2d94e85..e937aad 100644
--- a/fs/ext4/ialloc.c
+++ b/fs/ext4/ialloc.c
@@ -183,7 +183,16 @@ 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;
+ }
err = ext4_init_inode_bitmap(sb, bh, block_group, desc);
set_bitmap_uptodate(bh);
set_buffer_uptodate(bh);
@@ -960,7 +969,8 @@ struct inode *__ext4_new_inode(handle_t *handle, struct inode *dir,
/* 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 64056c6..4869946 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -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 {
@@ -2969,7 +2970,8 @@ 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 1f58179..97d322b 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -2991,13 +2991,22 @@ 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;
--
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