From fce466eab7ac6baa9d2dcd88abcf945be3d4a089 Mon Sep 17 00:00:00 2001 From: Qu Wenruo Date: Tue, 3 Jul 2018 17:10:05 +0800 Subject: btrfs: tree-checker: Verify block_group_item A crafted image with invalid block group items could make free space cache code to cause panic. We could detect such invalid block group item by checking: 1) Item size Known fixed value. 2) Block group size (key.offset) We have an upper limit on block group item (10G) 3) Chunk objectid Known fixed value. 4) Type Only 4 valid type values, DATA, METADATA, SYSTEM and DATA|METADATA. No more than 1 bit set for profile type. 5) Used space No more than the block group size. This should allow btrfs to detect and refuse to mount the crafted image. Link: https://bugzilla.kernel.org/show_bug.cgi?id=199849 Reported-by: Xu Wen Signed-off-by: Qu Wenruo Reviewed-by: Gu Jinxiang Reviewed-by: Nikolay Borisov Tested-by: Gu Jinxiang Reviewed-by: David Sterba Signed-off-by: David Sterba --- fs/btrfs/tree-checker.c | 100 ++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 100 insertions(+) (limited to 'fs/btrfs/tree-checker.c') diff --git a/fs/btrfs/tree-checker.c b/fs/btrfs/tree-checker.c index 8d40e7dd8c30..3bade2ad39e8 100644 --- a/fs/btrfs/tree-checker.c +++ b/fs/btrfs/tree-checker.c @@ -19,6 +19,7 @@ #include "tree-checker.h" #include "disk-io.h" #include "compression.h" +#include "volumes.h" /* * Error message should follow the following format: @@ -353,6 +354,102 @@ 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; + u64 type; + + /* + * Here we don't really care about alignment 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 > BTRFS_MAX_DATA_CHUNK_SIZE || key->offset == 0) { + block_group_err(fs_info, leaf, slot, + "invalid block group size, have %llu expect (0, %llu]", + key->offset, BTRFS_MAX_DATA_CHUNK_SIZE); + return -EUCLEAN; + } + + if (item_size != sizeof(bgi)) { + block_group_err(fs_info, leaf, slot, + "invalid item size, have %u expect %zu", + 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; + } + + type = flags & BTRFS_BLOCK_GROUP_TYPE_MASK; + if (type != BTRFS_BLOCK_GROUP_DATA && + type != BTRFS_BLOCK_GROUP_METADATA && + type != BTRFS_BLOCK_GROUP_SYSTEM && + type != (BTRFS_BLOCK_GROUP_METADATA | + BTRFS_BLOCK_GROUP_DATA)) { + block_group_err(fs_info, leaf, slot, +"invalid type, have 0x%llx (%lu bits set) expect either 0x%llx, 0x%llx, 0x%llu or 0x%llx", + type, hweight64(type), + BTRFS_BLOCK_GROUP_DATA, BTRFS_BLOCK_GROUP_METADATA, + BTRFS_BLOCK_GROUP_SYSTEM, + BTRFS_BLOCK_GROUP_METADATA | BTRFS_BLOCK_GROUP_DATA); + return -EUCLEAN; + } + return 0; +} + /* * Common point to switch the item-specific validation. */ @@ -374,6 +471,9 @@ 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; } -- cgit v1.2.3 From ba480dd4db9f1798541eb2d1c423fc95feee8d36 Mon Sep 17 00:00:00 2001 From: Qu Wenruo Date: Tue, 3 Jul 2018 17:10:06 +0800 Subject: btrfs: tree-checker: Detect invalid and empty essential trees A crafted image has empty root tree block, which will later cause NULL pointer dereference. The following trees should never be empty: 1) Tree root Must contain at least root items for extent tree, device tree and fs tree 2) Chunk tree Or we can't even bootstrap as it contains the mapping. 3) Fs tree At least inode item for top level inode (.). 4) Device tree Dev extents for chunks 5) Extent tree Must have corresponding extent for each chunk. If any of them is empty, we are sure the fs is corrupted and no need to mount it. Link: https://bugzilla.kernel.org/show_bug.cgi?id=199847 Reported-by: Xu Wen Signed-off-by: Qu Wenruo Tested-by: Gu Jinxiang Reviewed-by: David Sterba Signed-off-by: David Sterba --- fs/btrfs/tree-checker.c | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-) (limited to 'fs/btrfs/tree-checker.c') diff --git a/fs/btrfs/tree-checker.c b/fs/btrfs/tree-checker.c index 3bade2ad39e8..db835635372f 100644 --- a/fs/btrfs/tree-checker.c +++ b/fs/btrfs/tree-checker.c @@ -496,9 +496,22 @@ static int check_leaf(struct btrfs_fs_info *fs_info, struct extent_buffer *leaf, * skip this check for relocation trees. */ if (nritems == 0 && !btrfs_header_flag(leaf, BTRFS_HEADER_FLAG_RELOC)) { + u64 owner = btrfs_header_owner(leaf); struct btrfs_root *check_root; - key.objectid = btrfs_header_owner(leaf); + /* These trees must never be empty */ + if (owner == BTRFS_ROOT_TREE_OBJECTID || + owner == BTRFS_CHUNK_TREE_OBJECTID || + owner == BTRFS_EXTENT_TREE_OBJECTID || + owner == BTRFS_DEV_TREE_OBJECTID || + owner == BTRFS_FS_TREE_OBJECTID || + owner == BTRFS_DATA_RELOC_TREE_OBJECTID) { + generic_err(fs_info, leaf, 0, + "invalid root, root %llu must never be empty", + owner); + return -EUCLEAN; + } + key.objectid = owner; key.type = BTRFS_ROOT_ITEM_KEY; key.offset = (u64)-1; -- cgit v1.2.3