btrfs-corrupt-block already has a mix of generic and specific corruption options, but currently lacks the capacity for totally arbitrary corruption in item data.
There is already a flag for corruption size (bytes/-b), so add a flag for an offset and a value to memset the item with. Exercise the new flags with a new variant for -I (item) corruption. Look up the item as before, but instead of corrupting a field in the item struct, corrupt an offset/size in the item data. The motivating example for this is that in testing fsverity with btrfs, we need to corrupt the generated Merkle tree--metadata item data which is an opaque blob to btrfs. Signed-off-by: Boris Burkov <[email protected]> --- btrfs-corrupt-block.c | 71 +++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 68 insertions(+), 3 deletions(-) diff --git a/btrfs-corrupt-block.c b/btrfs-corrupt-block.c index 0c022a8e..bf1ce9c5 100644 --- a/btrfs-corrupt-block.c +++ b/btrfs-corrupt-block.c @@ -116,11 +116,13 @@ static void print_usage(int ret) printf("\t-m The metadata block to corrupt (must also specify -f for the field to corrupt)\n"); printf("\t-K <u64,u8,u64> Corrupt the given key (must also specify -f for the field and optionally -r for the root)\n"); printf("\t-f The field in the item to corrupt\n"); - printf("\t-I <u64,u8,u64> Corrupt an item corresponding to the passed key triplet (must also specify the field to corrupt and root for the item)\n"); + printf("\t-I <u64,u8,u64> Corrupt an item corresponding to the passed key triplet (must also specify the field, or bytes, offset, and value to corrupt and root for the item)\n"); printf("\t-D <u64,u8,u64> Corrupt a dir item corresponding to the passed key triplet, must also specify a field\n"); printf("\t-d <u64,u8,u64> Delete item corresponding to passed key triplet\n"); printf("\t-r Operate on this root\n"); printf("\t-C Delete a csum for the specified bytenr. When used with -b it'll delete that many bytes, otherwise it's just sectorsize\n"); + printf("\t-v Value to use for corrupting item data\n"); + printf("\t-o Offset to use for corrupting item data\n"); exit(ret); } @@ -896,6 +898,50 @@ out: return ret; } +static int corrupt_btrfs_item_data(struct btrfs_root *root, + struct btrfs_key *key, + u64 bogus_offset, u64 bogus_size, + char bogus_value) +{ + struct btrfs_trans_handle *trans; + struct btrfs_path *path; + int ret; + void *data; + struct extent_buffer *leaf; + int slot; + + path = btrfs_alloc_path(); + if (!path) + return -ENOMEM; + + trans = btrfs_start_transaction(root, 1); + if (IS_ERR(trans)) { + fprintf(stderr, "Couldn't start transaction %ld\n", + PTR_ERR(trans)); + ret = PTR_ERR(trans); + goto free_path; + } + + ret = btrfs_search_slot(trans, root, key, path, 0, 1); + if (ret != 0) { + fprintf(stderr, "Error searching to node %d\n", ret); + goto commit_txn; + } + leaf = path->nodes[0]; + slot = path->slots[0]; + data = btrfs_item_ptr(leaf, slot, void); + // TODO: check offset/size legitimacy + data += bogus_offset; + memset_extent_buffer(leaf, bogus_value, (unsigned long)data, bogus_size); + btrfs_mark_buffer_dirty(leaf); + +commit_txn: + btrfs_commit_transaction(trans, root); +free_path: + btrfs_free_path(path); + return ret; +} + static int delete_item(struct btrfs_root *root, struct btrfs_key *key) { struct btrfs_trans_handle *trans; @@ -1151,6 +1197,8 @@ int main(int argc, char **argv) u64 root_objectid = 0; u64 csum_bytenr = 0; char field[FIELD_BUF_LEN]; + u64 bogus_value = (u64)-1; + u64 bogus_offset = (u64)-1; field[0] = '\0'; memset(&key, 0, sizeof(key)); @@ -1177,11 +1225,13 @@ int main(int argc, char **argv) { "delete", no_argument, NULL, 'd'}, { "root", no_argument, NULL, 'r'}, { "csum", required_argument, NULL, 'C'}, + { "value", required_argument, NULL, 'v'}, + { "offset", required_argument, NULL, 'o'}, { "help", no_argument, NULL, GETOPT_VAL_HELP}, { NULL, 0, NULL, 0 } }; - c = getopt_long(argc, argv, "l:c:b:eEkuUi:f:x:m:K:I:D:d:r:C:", + c = getopt_long(argc, argv, "l:c:b:eEkuUi:f:x:m:K:I:D:d:r:C:v:o:", long_options, NULL); if (c < 0) break; @@ -1244,6 +1294,12 @@ int main(int argc, char **argv) case 'C': csum_bytenr = arg_strtou64(optarg); break; + case 'v': + bogus_value = arg_strtou64(optarg); + break; + case 'o': + bogus_offset = arg_strtou64(optarg); + break; case GETOPT_VAL_HELP: default: print_usage(c != GETOPT_VAL_HELP); @@ -1368,7 +1424,16 @@ int main(int argc, char **argv) if (!root_objectid) print_usage(1); - ret = corrupt_btrfs_item(target_root, &key, field); + if (*field != 0) + ret = corrupt_btrfs_item(target_root, &key, field); + else if (bogus_offset != (u64)-1 && + bytes != (u64)-1 && + bogus_value != (u64)-1) + ret = corrupt_btrfs_item_data(target_root, &key, + bogus_offset, bytes, + bogus_value); + else + print_usage(1); goto out_close; } if (delete) { -- 2.24.1
