Merge branch 'ps/fsck-stream-from-the-right-object-instance'

"fsck" iterates over packfiles and its access to pack data caused
the list to be permuted, which caused it to loop forever; the code
to access pack data by "fsck" has been updated to avoid this.

* ps/fsck-stream-from-the-right-object-instance:
  pack-check: fix verification of large objects
  packfile: expose function to read object stream for an offset
  object-file: adapt `stream_object_signature()` to take a stream
  t/helper: improve "genrandom" test helper

Author: gitster

object-file.c

@@ -129,18 +129,15 @@ int check_object_signature(struct repository *r, const struct object_id *oid,
 	return !oideq(oid, &real_oid) ? -1 : 0;
 }
 
-int stream_object_signature(struct repository *r, const struct object_id *oid)
+int stream_object_signature(struct repository *r,
+			    struct odb_read_stream *st,
+			    const struct object_id *oid)
 {
 	struct object_id real_oid;
-	struct odb_read_stream *st;
 	struct git_hash_ctx c;
 	char hdr[MAX_HEADER_LEN];
 	int hdrlen;
 
-	st = odb_read_stream_open(r->objects, oid, NULL);
-	if (!st)
-		return -1;
-
 	/* Generate the header */
 	hdrlen = format_object_header(hdr, sizeof(hdr), st->type, st->size);
 
@@ -160,7 +157,6 @@ int stream_object_signature(struct repository *r, const struct object_id *oid)
 		git_hash_update(&c, buf, readlen);
 	}
 	git_hash_final_oid(&real_oid, &c);
-	odb_read_stream_close(st);
 	return !oideq(oid, &real_oid) ? -1 : 0;
 }
 

object-file.h

@@ -166,7 +166,9 @@ int check_object_signature(struct repository *r, const struct object_id *oid,
  * Try reading the object named with "oid" using
  * the streaming interface and rehash it to do the same.
  */
-int stream_object_signature(struct repository *r, const struct object_id *oid);
+int stream_object_signature(struct repository *r,
+			    struct odb_read_stream *stream,
+			    const struct object_id *oid);
 
 enum finalize_object_file_flags {
 	FOF_SKIP_COLLISION_CHECK = 1,

object.c

@@ -6,6 +6,7 @@
 #include "object.h"
 #include "replace-object.h"
 #include "object-file.h"
+#include "odb/streaming.h"
 #include "blob.h"
 #include "statinfo.h"
 #include "tree.h"
@@ -343,9 +344,21 @@ struct object *parse_object_with_flags(struct repository *r,
 
 	if ((!obj || obj->type == OBJ_NONE || obj->type == OBJ_BLOB) &&
 	    odb_read_object_info(r->objects, oid, NULL) == OBJ_BLOB) {
-		if (!skip_hash && stream_object_signature(r, repl) < 0) {
-			error(_("hash mismatch %s"), oid_to_hex(oid));
-			return NULL;
+		if (!skip_hash) {
+			struct odb_read_stream *stream = odb_read_stream_open(r->objects, oid, NULL);
+
+			if (!stream) {
+				error(_("unable to open object stream for %s"), oid_to_hex(oid));
+				return NULL;
+			}
+
+			if (stream_object_signature(r, stream, repl) < 0) {
+				error(_("hash mismatch %s"), oid_to_hex(oid));
+				odb_read_stream_close(stream);
+				return NULL;
+			}
+
+			odb_read_stream_close(stream);
 		}
 		parse_blob_buffer(lookup_blob(r, oid));
 		return lookup_object(r, oid);

pack-check.c

@@ -9,6 +9,7 @@
 #include "packfile.h"
 #include "object-file.h"
 #include "odb.h"
+#include "odb/streaming.h"
 
 struct idx_entry {
 	off_t                offset;
@@ -104,6 +105,7 @@ static int verify_packfile(struct repository *r,
 	QSORT(entries, nr_objects, compare_entries);
 
 	for (i = 0; i < nr_objects; i++) {
+		struct odb_read_stream *stream = NULL;
 		void *data;
 		struct object_id oid;
 		enum object_type type;
@@ -152,7 +154,9 @@ static int verify_packfile(struct repository *r,
 							type) < 0)
 			err = error("packed %s from %s is corrupt",
 				    oid_to_hex(&oid), p->pack_name);
-		else if (!data && stream_object_signature(r, &oid) < 0)
+		else if (!data &&
+			 (packfile_read_object_stream(&stream, &oid, p, entries[i].offset) < 0 ||
+			  stream_object_signature(r, stream, &oid) < 0))
 			err = error("packed %s from %s is corrupt",
 				    oid_to_hex(&oid), p->pack_name);
 		else if (fn) {
@@ -163,12 +167,14 @@ static int verify_packfile(struct repository *r,
 		}
 		if (((base_count + i) & 1023) == 0)
 			display_progress(progress, base_count + i);
-		free(data);
 
+		if (stream)
+			odb_read_stream_close(stream);
+		free(data);
 	}
+
 	display_progress(progress, base_count + i);
 	free(entries);
-
 	return err;
 }
 

packfile.c

@@ -2621,32 +2621,28 @@ static int close_istream_pack_non_delta(struct odb_read_stream *_st)
 	return 0;
 }
 
-int packfile_store_read_object_stream(struct odb_read_stream **out,
-				      struct packfile_store *store,
-				      const struct object_id *oid)
+int packfile_read_object_stream(struct odb_read_stream **out,
+				const struct object_id *oid,
+				struct packed_git *pack,
+				off_t offset)
 {
 	struct odb_packed_read_stream *stream;
 	struct pack_window *window = NULL;
-	struct object_info oi = OBJECT_INFO_INIT;
 	enum object_type in_pack_type;
 	unsigned long size;
 
-	oi.sizep = &size;
+	in_pack_type = unpack_object_header(pack, &window, &offset, &size);
+	unuse_pack(&window);
 
-	if (packfile_store_read_object_info(store, oid, &oi, 0) ||
-	    oi.u.packed.type == PACKED_OBJECT_TYPE_REF_DELTA ||
-	    oi.u.packed.type == PACKED_OBJECT_TYPE_OFS_DELTA ||
-	    repo_settings_get_big_file_threshold(store->source->odb->repo) >= size)
+	if (repo_settings_get_big_file_threshold(pack->repo) >= size)
 		return -1;
 
-	in_pack_type = unpack_object_header(oi.u.packed.pack,
-					    &window,
-					    &oi.u.packed.offset,
-					    &size);
-	unuse_pack(&window);
 	switch (in_pack_type) {
 	default:
 		return -1; /* we do not do deltas for now */
+	case OBJ_BAD:
+		mark_bad_packed_object(pack, oid);
+		return -1;
 	case OBJ_COMMIT:
 	case OBJ_TREE:
 	case OBJ_BLOB:
@@ -2660,10 +2656,22 @@ int packfile_store_read_object_stream(struct odb_read_stream **out,
 	stream->base.type = in_pack_type;
 	stream->base.size = size;
 	stream->z_state = ODB_PACKED_READ_STREAM_UNINITIALIZED;
-	stream->pack = oi.u.packed.pack;
-	stream->pos = oi.u.packed.offset;
+	stream->pack = pack;
+	stream->pos = offset;
 
 	*out = &stream->base;
 
 	return 0;
 }
+
+int packfile_store_read_object_stream(struct odb_read_stream **out,
+				      struct packfile_store *store,
+				      const struct object_id *oid)
+{
+	struct pack_entry e;
+
+	if (!find_pack_entry(store, oid, &e))
+		return -1;
+
+	return packfile_read_object_stream(out, oid, e.p, e.offset);
+}

packfile.h

@@ -449,6 +449,11 @@ off_t get_delta_base(struct packed_git *p, struct pack_window **w_curs,
 		     off_t *curpos, enum object_type type,
 		     off_t delta_obj_offset);
 
+int packfile_read_object_stream(struct odb_read_stream **out,
+				const struct object_id *oid,
+				struct packed_git *pack,
+				off_t offset);
+
 void release_pack_memory(size_t);
 
 /* global flag to enable extra checks when accessing packed objects */

t/helper/test-genrandom.c

@@ -6,6 +6,7 @@
 
 #include "test-tool.h"
 #include "git-compat-util.h"
+#include "parse.h"
 
 int cmd__genrandom(int argc, const char **argv)
 {
@@ -22,7 +23,9 @@ int cmd__genrandom(int argc, const char **argv)
 		next = next * 11 + *c;
 	} while (*c++);
 
-	count = (argc == 3) ? strtoul(argv[2], NULL, 0) : ULONG_MAX;
+	count = ULONG_MAX;
+	if (argc == 3 && !git_parse_ulong(argv[2], &count))
+		return error_errno("cannot parse argument '%s'", argv[2]);
 
 	while (count--) {
 		next = next * 1103515245 + 12345;

t/t1006-cat-file.sh

@@ -643,7 +643,7 @@ test_expect_success 'object reference via commit text search' '
 '
 
 test_expect_success 'setup blobs which are likely to delta' '
-	test-tool genrandom foo 10240 >foo &&
+	test-tool genrandom foo 10k >foo &&
 	{ cat foo && echo plus; } >foo-plus &&
 	git add foo foo-plus &&
 	git commit -m foo &&

t/t1050-large.sh

@@ -104,9 +104,9 @@ test_expect_success 'packsize limit' '
 		# mid1 and mid2 will fit within 256k limit but
 		# appending mid3 will bust the limit and will
 		# result in a separate packfile.
-		test-tool genrandom "a" $(( 66 * 1024 )) >mid1 &&
-		test-tool genrandom "b" $(( 80 * 1024 )) >mid2 &&
-		test-tool genrandom "c" $(( 128 * 1024 )) >mid3 &&
+		test-tool genrandom "a" 66k >mid1 &&
+		test-tool genrandom "b" 80k >mid2 &&
+		test-tool genrandom "c" 128k >mid3 &&
 		git add mid1 mid2 mid3 &&
 
 		count=0 &&

t/t1450-fsck.sh

@@ -852,6 +852,44 @@ test_expect_success 'fsck errors in packed objects' '
 	! grep corrupt out
 '
 
+test_expect_success 'fsck handles multiple packfiles with big blobs' '
+	test_when_finished "rm -rf repo" &&
+	git init repo &&
+	(
+		cd repo &&
+
+		# We construct two packfiles with two objects in common and one
+		# object not in common. The objects in common can then be
+		# corrupted in one of the packfiles, respectively. The other
+		# objects that are unique to the packs are merely used to not
+		# have both packs contain the same data.
+		blob_one=$(test-tool genrandom one 200k | git hash-object -t blob -w --stdin) &&
+		blob_two=$(test-tool genrandom two 200k | git hash-object -t blob -w --stdin) &&
+		blob_three=$(test-tool genrandom three 200k | git hash-object -t blob -w --stdin) &&
+		blob_four=$(test-tool genrandom four 200k | git hash-object -t blob -w --stdin) &&
+		pack_one=$(printf "%s\n" "$blob_one" "$blob_two" "$blob_three" | git pack-objects .git/objects/pack/pack) &&
+		pack_two=$(printf "%s\n" "$blob_two" "$blob_three" "$blob_four" | git pack-objects .git/objects/pack/pack) &&
+		chmod a+w .git/objects/pack/pack-*.pack &&
+
+		# Corrupt blob two in the first pack.
+		git verify-pack -v .git/objects/pack/pack-$pack_one >objects &&
+		offset_one=$(sed <objects -n "s/^$blob_two .* \(.*\)$/\1/p") &&
+		printf "\0" | dd of=.git/objects/pack/pack-$pack_one.pack bs=1 conv=notrunc seek=$offset_one &&
+
+		# Corrupt blob three in the second pack.
+		git verify-pack -v .git/objects/pack/pack-$pack_two >objects &&
+		offset_two=$(sed <objects -n "s/^$blob_three .* \(.*\)$/\1/p") &&
+		printf "\0" | dd of=.git/objects/pack/pack-$pack_two.pack bs=1 conv=notrunc seek=$offset_two &&
+
+		# We now expect to see two failures for the corrupted objects,
+		# even though they exist in a non-corrupted form in the
+		# respective other pack.
+		test_must_fail git -c core.bigFileThreshold=100k fsck 2>err &&
+		test_grep "unknown object type 0 at offset $offset_one in .git/objects/pack/pack-$pack_one.pack" err &&
+		test_grep "unknown object type 0 at offset $offset_two in .git/objects/pack/pack-$pack_two.pack" err
+	)
+'
+
 test_expect_success 'fsck fails on corrupt packfile' '
 	hsh=$(git commit-tree -m mycommit HEAD^{tree}) &&
 	pack=$(echo $hsh | git pack-objects .git/objects/pack/pack) &&
@@ -918,7 +956,7 @@ test_expect_success 'fsck detects trailing loose garbage (large blob)' '
 test_expect_success 'fsck detects truncated loose object' '
 	# make it big enough that we know we will truncate in the data
 	# portion, not the header
-	test-tool genrandom truncate 4096 >file &&
+	test-tool genrandom truncate 4k >file &&
 	blob=$(git hash-object -w file) &&
 	file=$(sha1_file $blob) &&
 	test_when_finished "remove_object $blob" &&