fsck: avoid looking at NULL blob->object

Commit 159e7b080b (fsck: detect gitmodules files,
2018-05-02) taught fsck to look at the content of
.gitmodules files. If the object turns out not to be a blob
at all, we just complain and punt on checking the content.
And since this was such an obvious and trivial code path, I
didn't even bother to add a test.

Except it _does_ do one non-trivial thing, which is call the
report() function, which wants us to pass a pointer to a
"struct object". Which we don't have (we have only a "struct
object_id"). So we erroneously pass a NULL object to
report(), which gets dereferenced and causes a segfault.

It seems like we could refactor report() to just take the
object_id itself. But we pass the object pointer along to
a callback function, and indeed this ends up in
builtin/fsck.c's objreport() which does want to look at
other parts of the object (like the type).

So instead, let's just use lookup_unknown_object() to get
the real "struct object", and pass that.

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

diff --git a/fsck.c b/fsck.c
index 9339f315131786c50c9fa10dd702fe20562e167e..35af51553dbd2b04fbb57435eae44b42b04a00d0 100644 (file)
--- a/fsck.c
+++ b/fsck.c
@@ -1032,7 +1032,8 @@ int fsck_finish(struct fsck_options *options)
 
                blob = lookup_blob(oid);
                if (!blob) {
-                       ret |= report(options, &blob->object,
+                       struct object *obj = lookup_unknown_object(oid->hash);
+                       ret |= report(options, obj,
                                      FSCK_MSG_GITMODULES_BLOB,
                                      "non-blob found at .gitmodules");
                        continue;

diff --git a/t/t7415-submodule-names.sh b/t/t7415-submodule-names.sh
index 541bd81684e507fc80a7bf12a570af0a466be744..3c0f1a102a09e5c03cd6e270bbbf32d870b5c093 100755 (executable)
--- a/t/t7415-submodule-names.sh
+++ b/t/t7415-submodule-names.sh
@@ -148,4 +148,22 @@ test_expect_success 'fsck detects symlinked .gitmodules file' '
        )
 '
 
+test_expect_success 'fsck detects non-blob .gitmodules' '
+       git init non-blob &&
+       (
+               cd non-blob &&
+
+               # As above, make the funny tree directly to avoid index
+               # restrictions.
+               mkdir subdir &&
+               cp ../.gitmodules subdir/file &&
+               git add subdir/file &&
+               git commit -m ok &&
+               git ls-tree HEAD | sed s/subdir/.gitmodules/ | git mktree &&
+
+               test_must_fail git fsck 2>output &&
+               grep gitmodulesBlob output
+       )
+'
+
 test_done