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btrfs: tree-checker: Verify dev item

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[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: Yoon Jungyeon <jungyeon@gatech.edu>
Link: https://bugzilla.kernel.org/show_bug.cgi?id=202691
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Qu Wenruo 2019-03-08 14:20:03 +08:00 committed by David Sterba
parent 075cb3c78f
commit ab4ba2e133
3 changed files with 83 additions and 9 deletions
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74
fs/btrfs/tree-checker.c
View file

@ -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;
}

9
fs/btrfs/volumes.c
View file

@ -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)
{

9
fs/btrfs/volumes.h
View file

@ -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).