http-push: ensure unforced pushes fail when data would be lost

When we push using the DAV-based protocol, the client is the one that
performs the ref updates and therefore makes the checks to see whether
an unforced push should be allowed.  We make this check by determining
if either (a) we lack the object file for the old value of the ref or
(b) the new value of the ref is not newer than the old value, and in
either case, reject the push.

However, the ref_newer function, which performs this latter check, has
an odd behavior due to the reuse of certain object flags.  Specifically,
it will incorrectly return false in its first invocation and then
correctly return true on a subsequent invocation.  This occurs because
the object flags used by http-push.c are the same as those used by
commit-reach.c, which implements ref_newer, and one piece of code
misinterprets the flags set by the other.

Note that this does not occur in all cases.  For example, if the example
used in the tests is changed to use one repository instead of two and
rewind the head to add a commit, the test passes and we correctly reject
the push.  However, the example provided does trigger this behavior, and
the code has been broken in this way since at least Git 2.0.0.

To solve this problem, let's move the two sets of object flags so that
they don't overlap, since we're clearly using them at the same time.
The new set should not conflict with other usage because other users are
either builtin code (which is not compiled into git http-push) or
upload-pack (which we similarly do not use here).

Reported-by: Michael Ward <mward@smartsoftwareinc.com>
Signed-off-by: René Scharfe <l.s.r@web.de>
Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/http-push.c b/http-push.c
index 822f32659936d68de9bb7ee979a113fc12de2b65..99adbebdcf1f6e08840d6b4f364c2c0859577b03 100644 (file)
--- a/http-push.c
+++ b/http-push.c
@@ -70,10 +70,10 @@ enum XML_Status {
 #define LOCK_REFRESH 30
 
 /* Remember to update object flag allocation in object.h */
-#define LOCAL    (1u<<16)
-#define REMOTE   (1u<<17)
-#define FETCHING (1u<<18)
-#define PUSHING  (1u<<19)
+#define LOCAL    (1u<<11)
+#define REMOTE   (1u<<12)
+#define FETCHING (1u<<13)
+#define PUSHING  (1u<<14)
 
 /* We allow "recursive" symbolic refs. Only within reason, though */
 #define MAXDEPTH 5

diff --git a/object.h b/object.h
index 2dbabfca0ab8185f52cca6d3b7c69658e838ae49..ab81ab7abd940a356f0e055338051426c67e8db0 100644 (file)
--- a/object.h
+++ b/object.h
@@ -67,7 +67,7 @@ struct object_array {
  * builtin/blame.c:                        12-13
  * bisect.c:                                        16
  * bundle.c:                                        16
- * http-push.c:                                     16-----19
+ * http-push.c:                          11-----14
  * commit-graph.c:                                15
  * commit-reach.c:                                  16-----19
  * sha1-name.c:                                              20

diff --git a/t/t5540-http-push-webdav.sh b/t/t5540-http-push-webdav.sh
index d476c335098eef1e61aa8c7b8951fe760e8d13c1..450321fddbbf6aeb90ec8a257fd657d28a32cbf9 100755 (executable)
--- a/t/t5540-http-push-webdav.sh
+++ b/t/t5540-http-push-webdav.sh
@@ -126,6 +126,22 @@ test_expect_success 'create and delete remote branch' '
        test_must_fail git show-ref --verify refs/remotes/origin/dev
 '
 
+test_expect_success 'non-force push fails if not up to date' '
+       git init --bare "$HTTPD_DOCUMENT_ROOT_PATH"/test_repo_conflict.git &&
+       git -C "$HTTPD_DOCUMENT_ROOT_PATH"/test_repo_conflict.git update-server-info &&
+       git clone $HTTPD_URL/dumb/test_repo_conflict.git "$ROOT_PATH"/c1 &&
+       git clone $HTTPD_URL/dumb/test_repo_conflict.git "$ROOT_PATH"/c2 &&
+       test_commit -C "$ROOT_PATH/c1" path1 &&
+       git -C "$ROOT_PATH/c1" push origin HEAD &&
+       git -C "$ROOT_PATH/c2" pull &&
+       test_commit -C "$ROOT_PATH/c1" path2 &&
+       git -C "$ROOT_PATH/c1" push origin HEAD &&
+       test_commit -C "$ROOT_PATH/c2" path3 &&
+       git -C "$ROOT_PATH/c1" log --graph --all &&
+       git -C "$ROOT_PATH/c2" log --graph --all &&
+       test_must_fail git -C "$ROOT_PATH/c2" push origin HEAD
+'
+
 test_expect_success 'MKCOL sends directory names with trailing slashes' '
 
        ! grep "\"MKCOL.*[^/] HTTP/[^ ]*\"" < "$HTTPD_ROOT_PATH"/access.log