Merge branch 'jk/detect-truncated-zlib-input' into maint

A regression in Git 2.12 era made "git fsck" fall into an infinite
loop while processing truncated loose objects.

* jk/detect-truncated-zlib-input:
  cat-file: handle streaming failures consistently
  check_stream_sha1(): handle input underflow
  t1450: check large blob in trailing-garbage test

builtin/cat-file.c

@@ -50,6 +50,13 @@ static int filter_object(const char *path, unsigned mode,
 	return 0;
 }
 
+static int stream_blob(const struct object_id *oid)
+{
+	if (stream_blob_to_fd(1, oid, NULL, 0))
+		die("unable to stream %s to stdout", oid_to_hex(oid));
+	return 0;
+}
+
 static int cat_one_file(int opt, const char *exp_type, const char *obj_name,
 			int unknown_type)
 {
@@ -131,7 +138,7 @@ static int cat_one_file(int opt, const char *exp_type, const char *obj_name,
 		}
 
 		if (type == OBJ_BLOB)
-			return stream_blob_to_fd(1, &oid, NULL, 0);
+			return stream_blob(&oid);
 		buf = read_object_file(&oid, &type, &size);
 		if (!buf)
 			die("Cannot read object %s", obj_name);
@@ -154,7 +161,7 @@ static int cat_one_file(int opt, const char *exp_type, const char *obj_name,
 				oidcpy(&blob_oid, &oid);
 
 			if (oid_object_info(the_repository, &blob_oid, NULL) == OBJ_BLOB)
-				return stream_blob_to_fd(1, &blob_oid, NULL, 0);
+				return stream_blob(&blob_oid);
 			/*
 			 * we attempted to dereference a tag to a blob
 			 * and failed; there may be new dereference
@@ -317,8 +324,9 @@ static void print_object_or_die(struct batch_options *opt, struct expand_data *d
 				BUG("invalid cmdmode: %c", opt->cmdmode);
 			batch_write(opt, contents, size);
 			free(contents);
-		} else if (stream_blob_to_fd(1, oid, NULL, 0) < 0)
+		} else {
-			die("unable to stream %s to stdout", oid_to_hex(oid));
+			stream_blob(oid);
+		}
 	}
 	else {
 		enum object_type type;

sha1-file.c

@@ -2191,7 +2191,8 @@ static int check_stream_sha1(git_zstream *stream,
 	 * see the comment in unpack_sha1_rest for details.
 	 */
 	while (total_read <= size &&
-	       (status == Z_OK || status == Z_BUF_ERROR)) {
+	       (status == Z_OK ||
+		(status == Z_BUF_ERROR && !stream->avail_out))) {
 		stream->next_out = buf;
 		stream->avail_out = sizeof(buf);
 		if (size - total_read < stream->avail_out)

t/t1450-fsck.sh

@@ -673,16 +673,35 @@ test_expect_success 'fsck detects trailing loose garbage (commit)' '
 	test_i18ngrep "garbage.*$commit" out
 '
 
-test_expect_success 'fsck detects trailing loose garbage (blob)' '
+test_expect_success 'fsck detects trailing loose garbage (large blob)' '
 	blob=$(echo trailing | git hash-object -w --stdin) &&
 	file=$(sha1_file $blob) &&
 	test_when_finished "remove_object $blob" &&
 	chmod +w "$file" &&
 	echo garbage >>"$file" &&
-	test_must_fail git fsck 2>out &&
+	test_must_fail git -c core.bigfilethreshold=5 fsck 2>out &&
 	test_i18ngrep "garbage.*$blob" out
 '
 
+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 &&
+	blob=$(git hash-object -w file) &&
+	file=$(sha1_file $blob) &&
+	test_when_finished "remove_object $blob" &&
+	test_copy_bytes 1024 <"$file" >tmp &&
+	rm "$file" &&
+	mv -f tmp "$file" &&
+
+	# check both regular and streaming code paths
+	test_must_fail git fsck 2>out &&
+	test_i18ngrep corrupt.*$blob out &&
+
+	test_must_fail git -c core.bigfilethreshold=128 fsck 2>out &&
+	test_i18ngrep corrupt.*$blob out
+'
+
 # for each of type, we have one version which is referenced by another object
 # (and so while unreachable, not dangling), and another variant which really is
 # dangling.