[PATCH] fix(clone): segment fault when using --revision and protocol v0/v1

["NitroCao via GitGitGadget" <gitgitgadget@gmail.com>]

From: Nitro Cao <jaycecao520@gmail.com>

git clone command would segment fault when satisfying the following
conditions at the same time:
  - Use HTTP protocol v0 or v1 to interact with remote servers.
  - The value of `--revision` doesn't specify the peer reference, like
    `--revision master` instead of `--revision refs/heads/master:master`

When using protocol v2, git client can use `ref-prefix` param of
`ls-refs` command to fetch wanted references based on `--revision`.
But for protocol v0/v1, git client just fetch all references and
doesn't filter them.
In this case, the value of `remote_head` variable is not NULL,
which leads to the value of `remote_head_points_at` not NULL too.
But we don't specify the peer reference in `--revsion`,
`remote_head_points_at->peer_ref` would be NULL. So git client would
boom when `update_remote_refs`.

Signed-off-by: Nitro Cao <jaycecao520@gmail.com>
---
    fix(clone): segment fault when using --revision and protocol v0/v1
    
    git clone command would segment fault when satisfying the following
    conditions at the same time:
    
     * Use HTTP protocol v0 or v1 to interact with remote servers.
     * The value of --revision doesn't specify the peer reference, like
       --revision master instead of --revision refs/heads/master:master
    
    When using protocol v2, git client can use ref-prefix param of ls-refs
    command to fetch wanted references based on --revision. But for protocol
    v0/v1, git client just fetch all references and doesn't filter them. In
    this case, the value of remote_head variable is not NULL, which leads to
    the value of remote_head_points_at not NULL too. But we don't specify
    the peer reference in --revsion, remote_head_points_at->peer_ref would
    be NULL. So git client would boom when update_remote_refs.

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-2185%2FNitroCao%2Ffix%2Fsegment-fault-with-revision-param-v1
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-2185/NitroCao/fix/segment-fault-with-revision-param-v1
Pull-Request: https://github.com/git/git/pull/2185

 builtin/clone.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/builtin/clone.c b/builtin/clone.c
index b40cee5968..ba8de92563 100644
--- a/builtin/clone.c
+++ b/builtin/clone.c
@@ -558,7 +558,7 @@ static void update_remote_refs(const struct ref *refs,
 			write_followtags(refs, msg);
 	}
 
-	if (remote_head_points_at && !option_bare) {
+	if (remote_head_points_at && remote_head_points_at->peer_ref && !option_bare) {
 		struct strbuf head_ref = STRBUF_INIT;
 		strbuf_addstr(&head_ref, branch_top);
 		strbuf_addstr(&head_ref, "HEAD");

base-commit: 22584464849815268419fd9d2eba307362360db1
-- 
gitgitgadget