Subject: Re: Segfault in "git remote show <remote-name>"

From: Clemens Buchacher <[email-masked]>
Date: Mon, 25 May 2009 21:01:21 +0200

Subject: [PATCH] fix segfault showing an empty remote

In case of an empty list, the search for its tail caused a
NULL-pointer dereference.

Reported-by: Erik Faye-Lund <[email-masked]>
Signed-off-by: Clemens Buchacher <[email-masked]>
---

On Mon, May 25, 2009 at 06:10:12PM +0200, Erik Faye-Lund wrote:
> I've been messing around a bit, trying to set up a gitosis repo to
> mirror one of my projects. Now, I added the remote to my project, but
> when running "git remote show <remote-name>", I'm getting a segfault
> in builtin-remote.c at line 303 ("while (ref->next)"), because ref
> itself is NULL.

This should fix it.

I simply copied this from other uses of match_refs. I wonder if this calls
for a find_link_ref_tail() function, but I didn't know where to put it.

Clemens

 builtin-remote.c  |    8 ++++----
 t/t5505-remote.sh |   10 ++++++++++
 2 files changed, 14 insertions(+), 4 deletions(-)

diff --git a/builtin-remote.c b/builtin-remote.c
index 71abf68..fda9a54 100644
--- a/builtin-remote.c
+++ b/builtin-remote.c
@@ -299,11 +299,11 @@ static int get_push_ref_states(const struct ref *remote_refs,
 		return 0;
 
 	local_refs = get_local_heads();
-	ref = push_map = copy_ref_list(remote_refs);
-	while (ref->next)
-		ref = ref->next;
-	push_tail = &ref->next;
+	push_map = copy_ref_list(remote_refs);
 
+	push_tail = &push_map;
+	while (*push_tail)
+		push_tail = &((*push_tail)->next);
 	match_refs(local_refs, push_map, &push_tail, remote->push_refspec_nr,
 		   remote->push_refspec, MATCH_REFS_NONE);
 
diff --git a/t/t5505-remote.sh b/t/t5505-remote.sh
index 5ec668d..e70246b 100755
--- a/t/t5505-remote.sh
+++ b/t/t5505-remote.sh
@@ -494,5 +494,15 @@ test_expect_success 'remote prune to cause a dangling symref' '
 	grep "dangling symref" err
 '
 
+test_expect_success 'show empty remote' '
+
+	test_create_repo empty &&
+	git clone empty empty-clone &&
+	(
+		cd empty-clone &&
+		git remote show origin
+	)
+'
+
 test_done
 
-- 
1.6.3.1.147.g637c3