send-pack: segfault fix on forced push

When pushing to overwrite a ref that points at a commit we do
not even have, the recent "terse push" patch tried to get a
unique abbreviation for the non-existent (from our point of
view) object, which resulted in strcpy(buf, NULL) and
segfaulted.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/builtin-send-pack.c b/builtin-send-pack.c
index c1fd3f5fbb912e0d663e91007158460df33f3098..5a0f5c681cb1141576564972c4ad3f7999a1ff27 100644 (file)
--- a/builtin-send-pack.c
+++ b/builtin-send-pack.c
@@ -365,8 +365,9 @@ static int do_send_pack(int in, int out, struct remote *remote, const char *dest
                        char quickref[83];
                        char type = ' ';
                        const char *msg = "";
-
-                       strcpy(quickref, find_unique_abbrev(ref->old_sha1, DEFAULT_ABBREV));
+                       const char *old_abb;
+                       old_abb = find_unique_abbrev(ref->old_sha1, DEFAULT_ABBREV);
+                       strcpy(quickref, old_abb ? old_abb : old_hex);
                        if (ref_newer(ref->peer_ref->new_sha1, ref->old_sha1))
                                strcat(quickref, "..");
                        else {

diff --git a/t/t5405-send-pack-rewind.sh b/t/t5405-send-pack-rewind.sh
new file mode 100755 (executable)
index 0000000..86abc62
--- /dev/null
+++ b/t/t5405-send-pack-rewind.sh
@@ -0,0 +1,42 @@
+#!/bin/sh
+
+test_description='forced push to replace commit we do not have'
+
+. ./test-lib.sh
+
+test_expect_success setup '
+
+       >file1 && git add file1 && test_tick &&
+       git commit -m Initial &&
+
+       mkdir another && (
+               cd another &&
+               git init &&
+               git fetch .. master:master
+       ) &&
+
+       >file2 && git add file2 && test_tick &&
+       git commit -m Second
+
+'
+
+test_expect_success 'non forced push should die not segfault' '
+
+       (
+               cd another &&
+               git push .. master:master
+               test $? = 1
+       )
+
+'
+
+test_expect_success 'forced push should succeed' '
+
+       (
+               cd another &&
+               git push .. +master:master
+       )
+
+'
+
+test_done