Subject: Re: Segfault in git reflog

From: Dennis Kaarsemaker <[email-masked]>
Date: Wed, 30 Dec 2015 13:28:06 +0100

On wo, 2015-12-30 at 18:28 +0700, Duy Nguyen wrote:
> On Wed, Dec 30, 2015 at 6:26 PM, Duy Nguyen <[email-masked]>
> wrote:
> > On Wed, Dec 30, 2015 at 6:17 PM, Dennis Kaarsemaker
> > <[email-masked]> wrote:
> >> On wo, 2015-12-30 at 10:24 +0100, Dennis Kaarsemaker wrote:
> >>> spirit:~/code/git (master)$ cat .git/logs/HEAD
> >>> 2635c2b8bfc9aec07b7f023d8e3b3d02df715344
> 54bc41416c5d3ecb978acb0df80d57aa3e54494c Dennis Kaarsemaker <
> [email-masked]> 1446765642 +0100
> >>> 74c855f87d25a5b5c12d0485ec77c785a1c734c5
> 54bc41416c5d3ecb978acb0df80d57aa3e54494c Dennis Kaarsemaker <
> [email-masked]> 1446765951 +0100  checkout: moving from
> 3c3d3f629a6176b401ebec455c5dd59ed1b5f910 to master
> 
> Ah... I came from a different angle and did not realize the tag sha1
> is from your reflog. So yeah maybe reflog parsing code should check
> object type first, don't assume it's a commit!

Something like this perhaps?

diff --git a/reflog-walk.c b/reflog-walk.c
index 85b8a54..cd538dd 100644
--- a/reflog-walk.c
+++ b/reflog-walk.c
@@ -25,6 +25,14 @@ static int read_one_reflog(unsigned char *osha1, unsigned char *nsha1,
 {
        struct complete_reflogs *array = cb_data;
        struct reflog_info *item;
+       struct object *obj;
+
+       obj = parse_object(osha1);
+       if(obj && obj->type != OBJ_COMMIT)
+               die(_("Broken reflog, %s is a %s, not a commit"), sha1_to_hex(obj->oid.hash), typename(obj->type));
+       obj = parse_object(nsha1);
+       if(obj && obj->type != OBJ_COMMIT)
+               die(_("Broken reflog, %s is a %s, not a commit"), sha1_to_hex(obj->oid.hash), typename(obj->type));
 
        ALLOC_GROW(array->items, array->nr + 1, array->alloc);
        item = array->items + array->nr;

That gives me:
fatal: Broken reflog, 74c855f87d25a5b5c12d0485ec77c785a1c734c5 is a tag, not a commit

-- 
Dennis Kaarsemaker
www.kaarsemaker.net