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btrfs: tree-checker: add checker for items in remap tree

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Add write-time checking of items in the remap tree, to catch errors
before they are written to disk.

We're checking:

* That remap items, remap backrefs, and identity remaps aren't written
  unless the REMAP_TREE incompat flag is set
* That identity remaps have a size of 0
* That remap items and remap backrefs have a size of sizeof(struct
  btrfs_remap_item)
* That the objectid for these items is aligned to the sector size
* That the offset for these items (i.e. the size of the remapping) isn't
  0 and is aligned to the sector size
* That objectid + offset doesn't overflow

Signed-off-by: Mark Harmstone <mark@harmstone.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Mark Harmstone 2026-03-03 15:59:12 +00:00 committed by David Sterba
parent 0e6a169c64
commit da08c02bc7
1 changed files with 70 additions and 0 deletions
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70
fs/btrfs/tree-checker.c
View File

@ -1879,6 +1879,71 @@ static int check_raid_stripe_extent(const struct extent_buffer *leaf,
return 0;
}
static int check_remap_key(const struct extent_buffer *leaf,
const struct btrfs_key *key, int slot)
{
const u32 item_size = btrfs_item_size(leaf, slot);
const u32 sectorsize = leaf->fs_info->sectorsize;
u64 end;
if (unlikely(!btrfs_fs_incompat(leaf->fs_info, REMAP_TREE))) {
generic_err(leaf, slot,
"remap key type %u present but REMAP_TREE incompat bit unset",
key->type);
return -EUCLEAN;
}
switch (key->type) {
case BTRFS_IDENTITY_REMAP_KEY:
if (unlikely(item_size != 0)) {
generic_err(leaf, slot,
"invalid item size for IDENTITY_REMAP, have %u expect 0",
item_size);
return -EUCLEAN;
}
break;
case BTRFS_REMAP_KEY:
case BTRFS_REMAP_BACKREF_KEY:
if (unlikely(item_size != sizeof(struct btrfs_remap_item))) {
generic_err(leaf, slot,
"invalid item size for remap key type %u, have %u expect %zu",
key->type, item_size,
sizeof(struct btrfs_remap_item));
return -EUCLEAN;
}
break;
}
if (unlikely(key->offset == 0)) {
generic_err(leaf, slot,
"invalid remap key length, have 0 expect nonzero");
return -EUCLEAN;
}
if (unlikely(!IS_ALIGNED(key->objectid, sectorsize))) {
generic_err(leaf, slot,
"invalid remap key objectid, have %llu expect aligned to %u",
key->objectid, sectorsize);
return -EUCLEAN;
}
if (unlikely(!IS_ALIGNED(key->offset, sectorsize))) {
generic_err(leaf, slot,
"invalid remap key offset (length), have %llu expect aligned to %u",
key->offset, sectorsize);
return -EUCLEAN;
}
if (unlikely(check_add_overflow(key->objectid, key->offset, &end))) {
generic_err(leaf, slot,
"remap key overflow, objectid %llu + offset %llu wraps",
key->objectid, key->offset);
return -EUCLEAN;
}
return 0;
}
static int check_dev_extent_item(const struct extent_buffer *leaf,
const struct btrfs_key *key,
int slot,
@ -2130,6 +2195,11 @@ static enum btrfs_tree_block_status check_leaf_item(struct extent_buffer *leaf,
case BTRFS_FREE_SPACE_BITMAP_KEY:
ret = check_free_space_bitmap(leaf, key, slot);
break;
case BTRFS_IDENTITY_REMAP_KEY:
case BTRFS_REMAP_KEY:
case BTRFS_REMAP_BACKREF_KEY:
ret = check_remap_key(leaf, key, slot);
break;
}
if (unlikely(ret))