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builtin/clone: fix segfault when using --revision with protocol v0 

Servers supporting protocol v2 do not advertise excess refs and honor
`transport_ls_refs_options.ref_prefixes` when

    $ git clone --revision=refs/heads/main $URL

contacts them, but when talking to a server that does not support
protocol v2 the client segfaults. This can also be observed when v0 is
enforced for example by

    $ git -c protocol.version=0 clone --revision=refs/heads/main $URL

In the protocol v2 case the server honors
`transport_ls_refs_options.ref_prefixes` and in `cmd_clone()` the linked
list `refs` returned by `transport_get_remote_refs()` only contains a
single item, which is the ref requested with the --revision argument.
Both `remote_head` returned by `find_ref_by_name()` and
`remote_head_points_at` returned by `guess_remote_head()` are NULL. The
guard in `update_remote_refs()` skips a the affected code because
`remote_head_points_at` is NULL.

In the protocol v0 case in `cmd_clone()` the linked list `refs` returned
by `transport_get_remote_refs()` contains many items, amongst others
"HEAD". `remote_head` returned by `find_ref_by_name()` is not NULL and
`remote_head_points_at` returned by `guess_remote_head()` is not NULL
but its field `peer_ref` is NULL. Because `remote_head_points_at` is not
NULL the guard in `update_remote_refs()` does not skip the affected code
and `remote_head_points_at->peer_ref->name` is accessed, which causes a
segfault later on.

Signed-off-by: Adrian Friedli <adrian.friedli@mt.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
jch
Adrian Friedli 2026-07-24 14:41:38 +02:00 committed by Junio C Hamano
parent e9019fcafe
commit 1034ad383f
2 changed files with 9 additions and 1 deletions
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2
builtin/clone.c
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@ -557,7 +557,7 @@ 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");

8
t/t5621-clone-revision.sh
View File

@ -90,6 +90,14 @@ test_expect_success 'clone with --revision and --bare' '
test_must_fail git -C dst config remote.origin.fetch
'

test_expect_success 'clone with --revision and protocol v0' '
test_when_finished "rm -rf dst" &&
git -c protocol.version=0 clone --no-local --revision=refs/heads/main . dst &&
git rev-parse refs/heads/main >expect &&
git -C dst rev-parse HEAD >actual &&
test_cmp expect actual
'

test_expect_success 'clone with --revision being a short raw commit hash' '
test_when_finished "rm -rf dst" &&
oid=$(git rev-parse --short refs/heads/feature) &&