Commit ab4ba2e1 authored by Qu Wenruo's avatar Qu Wenruo Committed by David Sterba
Browse files

btrfs: tree-checker: Verify dev item 



[BUG]
For fuzzed image whose DEV_ITEM has invalid total_bytes as 0, then
kernel will just panic:
  BUG: unable to handle kernel NULL pointer dereference at 0000000000000098
  #PF error: [normal kernel read fault]
  PGD 800000022b2bd067 P4D 800000022b2bd067 PUD 22b2bc067 PMD 0
  Oops: 0000 [#1] SMP PTI
  CPU: 0 PID: 1106 Comm: mount Not tainted 5.0.0-rc8+ #9
  RIP: 0010:btrfs_verify_dev_extents+0x2a5/0x5a0
  Call Trace:
   open_ctree+0x160d/0x2149
   btrfs_mount_root+0x5b2/0x680

[CAUSE]
If device extent verification finds a deivce with 0 total_bytes, then it
assumes it's a seed dummy, then search for seed devices.

But in this case, there is no seed device at all, causing NULL pointer.

[FIX]
Since this is caused by fuzzed image, let's go the tree-check way, just
add a new verification for device item.

Reported-by: default avatarYoon Jungyeon <jungyeon@gatech.edu>
Link: https://bugzilla.kernel.org/show_bug.cgi?id=202691


Reviewed-by: default avatarNikolay Borisov <nborisov@suse.com>
Signed-off-by: default avatarQu Wenruo <wqu@suse.com>
Reviewed-by: default avatarJohannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent 075cb3c7

fs/btrfs/tree-checker.c

+74 −0
Original line number Diff line number Diff line
@@ -600,6 +600,77 @@ int btrfs_check_chunk_valid(struct btrfs_fs_info *fs_info, 
	return 0;

}



__printf(4, 5)

__cold

static void dev_item_err(const struct btrfs_fs_info *fs_info,

			 const struct extent_buffer *eb, int slot,

			 const char *fmt, ...)

{

	struct btrfs_key key;

	struct va_format vaf;

	va_list args;



	btrfs_item_key_to_cpu(eb, &key, slot);

	va_start(args, fmt);



	vaf.fmt = fmt;

	vaf.va = &args;



	btrfs_crit(fs_info,

	"corrupt %s: root=%llu block=%llu slot=%d devid=%llu %pV",

		btrfs_header_level(eb) == 0 ? "leaf" : "node",

		btrfs_header_owner(eb), btrfs_header_bytenr(eb), slot,

		key.objectid, &vaf);

	va_end(args);

}



static int check_dev_item(struct btrfs_fs_info *fs_info,

			  struct extent_buffer *leaf,

			  struct btrfs_key *key, int slot)

{

	struct btrfs_dev_item *ditem;

	u64 max_devid = max(BTRFS_MAX_DEVS(fs_info), BTRFS_MAX_DEVS_SYS_CHUNK);



	if (key->objectid != BTRFS_DEV_ITEMS_OBJECTID) {

		dev_item_err(fs_info, leaf, slot,

			     "invalid objectid: has=%llu expect=%llu",

			     key->objectid, BTRFS_DEV_ITEMS_OBJECTID);

		return -EUCLEAN;

	}

	if (key->offset > max_devid) {

		dev_item_err(fs_info, leaf, slot,

			     "invalid devid: has=%llu expect=[0, %llu]",

			     key->offset, max_devid);

		return -EUCLEAN;

	}

	ditem = btrfs_item_ptr(leaf, slot, struct btrfs_dev_item);

	if (btrfs_device_id(leaf, ditem) != key->offset) {

		dev_item_err(fs_info, leaf, slot,

			     "devid mismatch: key has=%llu item has=%llu",

			     key->offset, btrfs_device_id(leaf, ditem));

		return -EUCLEAN;

	}



	/*

	 * For device total_bytes, we don't have reliable way to check it, as

	 * it can be 0 for device removal. Device size check can only be done

	 * by dev extents check.

	 */

	if (btrfs_device_bytes_used(leaf, ditem) >

	    btrfs_device_total_bytes(leaf, ditem)) {

		dev_item_err(fs_info, leaf, slot,

			     "invalid bytes used: have %llu expect [0, %llu]",

			     btrfs_device_bytes_used(leaf, ditem),

			     btrfs_device_total_bytes(leaf, ditem));

		return -EUCLEAN;

	}

	/*

	 * Remaining members like io_align/type/gen/dev_group aren't really

	 * utilized.  Skip them to make later usage of them easier.

	 */

	return 0;

}



/*

 * Common point to switch the item-specific validation.

 */
@@ -630,6 +701,9 @@ static int check_leaf_item(struct btrfs_fs_info *fs_info, 
		ret = btrfs_check_chunk_valid(fs_info, leaf, chunk,

					      key->offset);

		break;

	case BTRFS_DEV_ITEM_KEY:

		ret = check_dev_item(fs_info, leaf, key, slot);

		break;

	}

	return ret;

}

fs/btrfs/volumes.c

+0 −9
Original line number Diff line number Diff line
@@ -4958,15 +4958,6 @@ static void check_raid56_incompat_flag(struct btrfs_fs_info *info, u64 type) 
	btrfs_set_fs_incompat(info, RAID56);

}



#define BTRFS_MAX_DEVS(info) ((BTRFS_MAX_ITEM_SIZE(info)	\

			- sizeof(struct btrfs_chunk))		\

			/ sizeof(struct btrfs_stripe) + 1)



#define BTRFS_MAX_DEVS_SYS_CHUNK ((BTRFS_SYSTEM_CHUNK_ARRAY_SIZE	\

				- 2 * sizeof(struct btrfs_disk_key)	\

				- 2 * sizeof(struct btrfs_chunk))	\

				/ sizeof(struct btrfs_stripe) + 1)



static int __btrfs_alloc_chunk(struct btrfs_trans_handle *trans,

			       u64 start, u64 type)

{

fs/btrfs/volumes.h

+9 −0
Original line number Diff line number Diff line
@@ -258,6 +258,15 @@ struct btrfs_fs_devices { 


#define BTRFS_BIO_INLINE_CSUM_SIZE	64



#define BTRFS_MAX_DEVS(info) ((BTRFS_MAX_ITEM_SIZE(info)	\

			- sizeof(struct btrfs_chunk))		\

			/ sizeof(struct btrfs_stripe) + 1)



#define BTRFS_MAX_DEVS_SYS_CHUNK ((BTRFS_SYSTEM_CHUNK_ARRAY_SIZE	\

				- 2 * sizeof(struct btrfs_disk_key)	\

				- 2 * sizeof(struct btrfs_chunk))	\

				/ sizeof(struct btrfs_stripe) + 1)



/*

 * we need the mirror number and stripe index to be passed around

 * the call chain while we are processing end_io (especially errors).

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