parse_commit_buffer(): treat lookup_commit() failure as parse error

While parsing the parents of a commit, if we are able to parse an actual
oid but lookup_commit() fails on it (because we previously saw it in
this process as a different object type), we silently omit the parent
and do not report any error to the caller.

The caller has no way of knowing this happened, because even an empty
parent list is a valid parse result. As a result, it's possible to fool
our "rev-list" connectivity check into accepting a corrupted set of
objects.

There's a test for this case already in t6102, but unfortunately it has
a slight error. It creates a broken commit with a parent line pointing
to a blob, and then checks that rev-list notices the problem in two
cases:

  1. the "lone" case: we traverse the broken commit by itself (here we
     try to actually load the blob from disk and find out that it's not
     a commit)

  2. the "seen" case: we parse the blob earlier in the process, and then
     when calling lookup_commit() we realize immediately that it's not a
     commit

The "seen" variant for this test mistakenly parsed another commit
instead of the blob, meaning that we were actually just testing the
"lone" case again. Changing that reveals the breakage (and shows that
this fixes it).

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/commit.c b/commit.c
index 40890ae7ce8a48a2da06bcde6fc5a9db77260707..6467c9e175fad0ad0b60efdba6e4437940b974a1 100644 (file)
--- a/commit.c
+++ b/commit.c
@@ -432,8 +432,11 @@ int parse_commit_buffer(struct repository *r, struct commit *item, const void *b
                if (graft && (graft->nr_parent < 0 || grafts_replace_parents))
                        continue;
                new_parent = lookup_commit(r, &parent);
-               if (new_parent)
-                       pptr = &commit_list_insert(new_parent, pptr)->next;
+               if (!new_parent)
+                       return error("bad parent %s in commit %s",
+                                    oid_to_hex(&parent),
+                                    oid_to_hex(&item->object.oid));
+               pptr = &commit_list_insert(new_parent, pptr)->next;
        }
        if (graft) {
                int i;
@@ -442,7 +445,9 @@ int parse_commit_buffer(struct repository *r, struct commit *item, const void *b
                        new_parent = lookup_commit(r,
                                                   &graft->parent[i]);
                        if (!new_parent)
-                               continue;
+                               return error("bad graft parent %s in commit %s",
+                                            oid_to_hex(&graft->parent[i]),
+                                            oid_to_hex(&item->object.oid));
                        pptr = &commit_list_insert(new_parent, pptr)->next;
                }
        }

diff --git a/t/t6102-rev-list-unexpected-objects.sh b/t/t6102-rev-list-unexpected-objects.sh
index 28611c978e6c0094a5e452bf8c8c8778da02ae6c..52cde097dd5c1c473df987cf74f51da714bd17b4 100755 (executable)
--- a/t/t6102-rev-list-unexpected-objects.sh
+++ b/t/t6102-rev-list-unexpected-objects.sh
@@ -52,7 +52,7 @@ test_expect_success 'traverse unexpected non-commit parent (lone)' '
 '
 
 test_expect_success 'traverse unexpected non-commit parent (seen)' '
-       test_must_fail git rev-list --objects $commit $broken_commit \
+       test_must_fail git rev-list --objects $blob $broken_commit \
                >output 2>&1 &&
        test_i18ngrep "not a commit" output
 '