As reported in https://bugzilla.kernel.org/show_bug.cgi?id=199849,
a crafted image with invalid block group items could make free space cache
code to cause panic.
We could early detect such invalid block group item by checking:
1) Size (key)
We have a up limit on block group item (10G)
2) Chunk objectid
3) Type
Exactly 1 bit set for type and no more than 1 bit set for profile
4) Used space
No more than block group size.
This should allow btrfs to detect and refuse to mount the crafted image.
Reported-by: Xu Wen <wen...@gatech.edu>
Signed-off-by: Qu Wenruo <w...@suse.com>
---
changelog:
v2:
Format change for if() code block, added one new line for each block.
Use "hweight64() > 1" to detect profile error, replacing the bloated
!(flags & MASK == 0 || hweight64() == 1) condition.
---
fs/btrfs/tree-checker.c | 92 +++++++++++++++++++++++++++++++++++++++++
1 file changed, 92 insertions(+)
diff --git a/fs/btrfs/tree-checker.c b/fs/btrfs/tree-checker.c
index 8d40e7dd8c30..d4f872682668 100644
--- a/fs/btrfs/tree-checker.c
+++ b/fs/btrfs/tree-checker.c
@@ -353,6 +353,95 @@ static int check_dir_item(struct btrfs_fs_info *fs_info,
return 0;
}
+__printf(4, 5)
+__cold
+static void block_group_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 bg_start=%llu bg_len=%llu,
%pV",
+ btrfs_header_level(eb) == 0 ? "leaf" : "node",
+ btrfs_header_owner(eb), btrfs_header_bytenr(eb), slot,
+ key.objectid, key.offset, &vaf);
+ va_end(args);
+}
+
+static int check_block_group_item(struct btrfs_fs_info *fs_info,
+ struct extent_buffer *leaf,
+ struct btrfs_key *key, int slot)
+{
+ struct btrfs_block_group_item bgi;
+ u32 item_size = btrfs_item_size_nr(leaf, slot);
+ u64 flags;
+
+ /*
+ * Here we don't really care about unalignment since extent allocator
+ * can handle it.
+ * We care more about the size, as if one block group is larger than
+ * maximum size, it's must be some obvious corruption
+ */
+ if (key->offset > 10ULL * SZ_1G) {
+ block_group_err(fs_info, leaf, slot,
+ "invalid block group size, have %llu expect (0, %llu)",
+ key->offset, 10ULL * SZ_1G);
+ return -EUCLEAN;
+ }
+
+ if (item_size != sizeof(bgi)) {
+ block_group_err(fs_info, leaf, slot,
+ "invalid item size, have %u expect %lu",
+ item_size, sizeof(bgi));
+ return -EUCLEAN;
+ }
+
+ read_extent_buffer(leaf, &bgi, btrfs_item_ptr_offset(leaf, slot),
+ sizeof(bgi));
+ if (btrfs_block_group_chunk_objectid(&bgi) !=
+ BTRFS_FIRST_CHUNK_TREE_OBJECTID) {
+ block_group_err(fs_info, leaf, slot,
+ "invalid block group chunk objectid, have %llu expect %llu",
+ btrfs_block_group_chunk_objectid(&bgi),
+ BTRFS_FIRST_CHUNK_TREE_OBJECTID);
+ return -EUCLEAN;
+ }
+
+ if (btrfs_block_group_used(&bgi) > key->offset) {
+ block_group_err(fs_info, leaf, slot,
+ "invalid block group used, have %llu expect [0, %llu)",
+ btrfs_block_group_used(&bgi), key->offset);
+ return -EUCLEAN;
+ }
+
+ flags = btrfs_block_group_flags(&bgi);
+ if (hweight64(flags & BTRFS_BLOCK_GROUP_PROFILE_MASK) > 1) {
+ block_group_err(fs_info, leaf, slot,
+"invalid profile flags, have 0x%llx (%lu bits set) expect no more than 1 bit
set",
+ flags & BTRFS_BLOCK_GROUP_PROFILE_MASK,
+ hweight64(flags & BTRFS_BLOCK_GROUP_PROFILE_MASK));
+ return -EUCLEAN;
+ }
+
+ if (hweight64(flags & BTRFS_BLOCK_GROUP_TYPE_MASK) != 1) {
+ block_group_err(fs_info, leaf, slot,
+"invalid type flags, have 0x%llx (%lu bits set) expect exactly 1 bit set",
+ flags & BTRFS_BLOCK_GROUP_TYPE_MASK,
+ hweight64(flags & BTRFS_BLOCK_GROUP_TYPE_MASK));
+ return -EUCLEAN;
+ }
+ return 0;
+}
+
/*
* Common point to switch the item-specific validation.
*/
@@ -374,6 +463,9 @@ static int check_leaf_item(struct btrfs_fs_info *fs_info,
case BTRFS_XATTR_ITEM_KEY:
ret = check_dir_item(fs_info, leaf, key, slot);
break;
+ case BTRFS_BLOCK_GROUP_ITEM_KEY:
+ ret = check_block_group_item(fs_info, leaf, key, slot);
+ break;
}
return ret;
}
--
2.18.0
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