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upload-pack: use oidset for deepen_not list 

We record the oid of every deepen-not line the client sends to us. For a
well-behaved client, the resulting array should be bounded by the number
of unique refs we have. But because there's no de-duplication, a
malicious client can cause the array to grow unbounded by just sending
the same "refs/heads/foo" over and over (assuming such a ref exists).

Since the deepen-not list is just being fed to a "rev-list --not"
traversal, the order of items doesn't matter. So we can replace the
oid_array with an oidset which notices and skips duplicates.

That bounds the memory in malicious cases to be linear in the number of
unique refs. And even in non-malicious cases, there may be a slight
improvement in memory usage if multiple refs point to the same oid
(though in practice this list is probably pretty tiny anyway, as it
comes from the user specifying "--shallow-exclude" on the client fetch).

Note that in the trace2 output we'll now output the number of
de-duplicated objects, rather than the total number of "deepen-not"
lines we received. This is arguably a more useful value for tracing /
debugging anyway.

Reported-by: Benjamin Flesch <benjaminflesch@icloud.com>
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
maint
Jeff King 2024-02-28 17:37:44 -05:00 committed by Junio C Hamano
parent 720ba25d99
commit 388b96df31
1 changed files with 11 additions and 10 deletions
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21
upload-pack.c
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@ -65,7 +65,7 @@ struct upload_pack_data {
struct strvec hidden_refs;

struct object_array shallows;
struct oid_array deepen_not;
struct oidset deepen_not;
struct object_array extra_edge_obj;
int depth;
timestamp_t deepen_since;
@ -125,7 +125,7 @@ static void upload_pack_data_init(struct upload_pack_data *data)
struct object_array want_obj = OBJECT_ARRAY_INIT;
struct object_array have_obj = OBJECT_ARRAY_INIT;
struct object_array shallows = OBJECT_ARRAY_INIT;
struct oid_array deepen_not = OID_ARRAY_INIT;
struct oidset deepen_not = OID_ARRAY_INIT;
struct string_list uri_protocols = STRING_LIST_INIT_DUP;
struct object_array extra_edge_obj = OBJECT_ARRAY_INIT;
struct string_list allowed_filters = STRING_LIST_INIT_DUP;
@ -158,7 +158,7 @@ static void upload_pack_data_clear(struct upload_pack_data *data)
object_array_clear(&data->want_obj);
object_array_clear(&data->have_obj);
object_array_clear(&data->shallows);
oid_array_clear(&data->deepen_not);
oidset_clear(&data->deepen_not);
object_array_clear(&data->extra_edge_obj);
list_objects_filter_release(&data->filter_options);
string_list_clear(&data->allowed_filters, 0);
@ -923,12 +923,13 @@ static int send_shallow_list(struct upload_pack_data *data)
strvec_push(&av, "rev-list");
if (data->deepen_since)
strvec_pushf(&av, "--max-age=%"PRItime, data->deepen_since);
if (data->deepen_not.nr) {
if (oidset_size(&data->deepen_not)) {
const struct object_id *oid;
struct oidset_iter iter;
strvec_push(&av, "--not");
for (i = 0; i < data->deepen_not.nr; i++) {
struct object_id *oid = data->deepen_not.oid + i;
oidset_iter_init(&data->deepen_not, &iter);
while ((oid = oidset_iter_next(&iter)))
strvec_push(&av, oid_to_hex(oid));
}
strvec_push(&av, "--not");
}
for (i = 0; i < data->want_obj.nr; i++) {
@ -1004,7 +1005,7 @@ static int process_deepen_since(const char *line, timestamp_t *deepen_since, int
return 0;
}

static int process_deepen_not(const char *line, struct oid_array *deepen_not, int *deepen_rev_list)
static int process_deepen_not(const char *line, struct oidset *deepen_not, int *deepen_rev_list)
{
const char *arg;
if (skip_prefix(line, "deepen-not ", &arg)) {
@ -1012,7 +1013,7 @@ static int process_deepen_not(const char *line, struct oid_array *deepen_not, in
struct object_id oid;
if (expand_ref(the_repository, arg, strlen(arg), &oid, &ref) != 1)
die("git upload-pack: ambiguous deepen-not: %s", line);
oid_array_append(deepen_not, &oid);
oidset_insert(deepen_not, &oid);
free(ref);
*deepen_rev_list = 1;
return 1;
@ -1554,7 +1555,7 @@ static void trace2_fetch_info(struct upload_pack_data *data)
jw_object_intmax(&jw, "depth", data->depth);
jw_object_intmax(&jw, "shallows", data->shallows.nr);
jw_object_bool(&jw, "deepen-since", data->deepen_since);
jw_object_intmax(&jw, "deepen-not", data->deepen_not.nr);
jw_object_intmax(&jw, "deepen-not", oidset_size(&data->deepen_not));
jw_object_bool(&jw, "deepen-relative", data->deepen_relative);
if (data->filter_options.choice)
jw_object_string(&jw, "filter", list_object_filter_config_name(data->filter_options.choice));