Commit f333a3c7 authored by Qu Wenruo's avatar Qu Wenruo Committed by David Sterba
Browse files

btrfs: tree-checker: validate dref root and objectid 



[CORRUPTION]
There is a bug report that btrfs flips RO due to a corruption in the
extent tree, the involved dumps looks like this:

 	item 188 key (402811572224 168 4096) itemoff 14598 itemsize 79
 		extent refs 3 gen 3678544 flags 1
 		ref#0: extent data backref root 13835058055282163977 objectid 281473384125923 offset 81432576 count 1
 		ref#1: shared data backref parent 1947073626112 count 1
 		ref#2: shared data backref parent 1156030103552 count 1
 BTRFS critical (device vdc1: state EA): unable to find ref byte nr 402811572224 parent 0 root 265 owner 28703026 offset 81432576 slot 189
 BTRFS error (device vdc1: state EA): failed to run delayed ref for logical 402811572224 num_bytes 4096 type 178 action 2 ref_mod 1: -2

[CAUSE]
The corrupted entry is ref#0 of item 188.
The root number 13835058055282163977 is beyond the upper limit for root
items (the current limit is 1 << 48), and the objectid also looks
suspicious.

Only the offset and count is correct.

[ENHANCEMENT]
Although it's still unknown why we have such many bytes corrupted
randomly, we can still enhance the tree-checker for data backrefs by:

- Validate the root value
  For now there should only be 3 types of roots can have data backref:
  * subvolume trees
  * data reloc trees
  * root tree
    Only for v1 space cache

- validate the objectid value
  The objectid should be a valid inode number.

Hopefully we can catch such problem in the future with the new checkers.

Reported-by: default avatarKai Krakow <hurikhan77@gmail.com>
Link: https://lore.kernel.org/linux-btrfs/CAMthOuPjg5RDT-G_LXeBBUUtzt3cq=JywF+D1_h+JYxe=WKp-Q@mail.gmail.com/#t


Reviewed-by: default avatarFilipe Manana <fdmanana@suse.com>
Signed-off-by: default avatarQu Wenruo <wqu@suse.com>
Reviewed-by: default avatarDavid Sterba <dsterba@suse.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent c3ece6b7

fs/btrfs/tree-checker.c

+47 −0
Original line number Diff line number Diff line
@@ -1289,6 +1289,19 @@ static void extent_err(const struct extent_buffer *eb, int slot, 
	va_end(args);

}



static bool is_valid_dref_root(u64 rootid)

{

	/*

	 * The following tree root objectids are allowed to have a data backref:

	 * - subvolume trees

	 * - data reloc tree

	 * - tree root

	 *   For v1 space cache

	 */

	return is_fstree(rootid) || rootid == BTRFS_DATA_RELOC_TREE_OBJECTID ||

	       rootid == BTRFS_ROOT_TREE_OBJECTID;

}



static int check_extent_item(struct extent_buffer *leaf,

			     struct btrfs_key *key, int slot,

			     struct btrfs_key *prev_key)
@@ -1441,6 +1454,8 @@ static int check_extent_item(struct extent_buffer *leaf, 
		struct btrfs_extent_data_ref *dref;

		struct btrfs_shared_data_ref *sref;

		u64 seq;

		u64 dref_root;

		u64 dref_objectid;

		u64 dref_offset;

		u64 inline_offset;

		u8 inline_type;
@@ -1484,11 +1499,26 @@ static int check_extent_item(struct extent_buffer *leaf, 
		 */

		case BTRFS_EXTENT_DATA_REF_KEY:

			dref = (struct btrfs_extent_data_ref *)(&iref->offset);

			dref_root = btrfs_extent_data_ref_root(leaf, dref);

			dref_objectid = btrfs_extent_data_ref_objectid(leaf, dref);

			dref_offset = btrfs_extent_data_ref_offset(leaf, dref);

			seq = hash_extent_data_ref(

					btrfs_extent_data_ref_root(leaf, dref),

					btrfs_extent_data_ref_objectid(leaf, dref),

					btrfs_extent_data_ref_offset(leaf, dref));

			if (unlikely(!is_valid_dref_root(dref_root))) {

				extent_err(leaf, slot,

					   "invalid data ref root value %llu",

					   dref_root);

				return -EUCLEAN;

			}

			if (unlikely(dref_objectid < BTRFS_FIRST_FREE_OBJECTID ||

				     dref_objectid > BTRFS_LAST_FREE_OBJECTID)) {

				extent_err(leaf, slot,

					   "invalid data ref objectid value %llu",

					   dref_root);

				return -EUCLEAN;

			}

			if (unlikely(!IS_ALIGNED(dref_offset,

						 fs_info->sectorsize))) {

				extent_err(leaf, slot,
@@ -1627,6 +1657,8 @@ static int check_extent_data_ref(struct extent_buffer *leaf, 
		return -EUCLEAN;

	}

	for (; ptr < end; ptr += sizeof(*dref)) {

		u64 root;

		u64 objectid;

		u64 offset;



		/*
@@ -1634,7 +1666,22 @@ static int check_extent_data_ref(struct extent_buffer *leaf, 
		 * overflow from the leaf due to hash collisions.

		 */

		dref = (struct btrfs_extent_data_ref *)ptr;

		root = btrfs_extent_data_ref_root(leaf, dref);

		objectid = btrfs_extent_data_ref_objectid(leaf, dref);

		offset = btrfs_extent_data_ref_offset(leaf, dref);

		if (unlikely(!is_valid_dref_root(root))) {

			extent_err(leaf, slot,

				   "invalid extent data backref root value %llu",

				   root);

			return -EUCLEAN;

		}

		if (unlikely(objectid < BTRFS_FIRST_FREE_OBJECTID ||

			     objectid > BTRFS_LAST_FREE_OBJECTID)) {

			extent_err(leaf, slot,

				   "invalid extent data backref objectid value %llu",

				   root);

			return -EUCLEAN;

		}

		if (unlikely(!IS_ALIGNED(offset, leaf->fs_info->sectorsize))) {

			extent_err(leaf, slot,

	"invalid extent data backref offset, have %llu expect aligned to %u",