git/promisor-remote.c
Emily Shaffer 65904b8b2b promisor-remote: skip move_to_tail when no-op
Previously, when promisor_remote_move_to_tail() is called for a
promisor_remote which is currently the final element in promisors, a
cycle is created in the promisors linked list. This cycle leads to a
double free later on in promisor_remote_clear() when the final element
of the promisors list is removed: promisors is set to promisors->next (a
no-op, as promisors->next == promisors); the previous value of promisors
is free()'d; then the new value of promisors (which is equal to the
previous value of promisors) is also free()'d. This double-free error
was unrecoverable for the user without removing the filter or re-cloning
the repo and hoping to miss this edge case.

Now, when promisor_remote_move_to_tail() would be a no-op, just do a
no-op. In cases of promisor_remote_move_to_tail() where r is not already
at the tail of the list, it works as before.

Helped-by: Jeff King <peff@peff.net>
Signed-off-by: Emily Shaffer <emilyshaffer@google.com>
Acked-by: Christian Couder <christian.couder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2019-10-02 14:56:54 +09:00

268 lines
5.6 KiB
C

#include "cache.h"
#include "object-store.h"
#include "promisor-remote.h"
#include "config.h"
#include "transport.h"
static char *repository_format_partial_clone;
static const char *core_partial_clone_filter_default;
void set_repository_format_partial_clone(char *partial_clone)
{
repository_format_partial_clone = xstrdup_or_null(partial_clone);
}
static int fetch_refs(const char *remote_name, struct ref *ref)
{
struct remote *remote;
struct transport *transport;
int original_fetch_if_missing = fetch_if_missing;
int res;
fetch_if_missing = 0;
remote = remote_get(remote_name);
if (!remote->url[0])
die(_("Remote with no URL"));
transport = transport_get(remote, remote->url[0]);
transport_set_option(transport, TRANS_OPT_FROM_PROMISOR, "1");
transport_set_option(transport, TRANS_OPT_NO_DEPENDENTS, "1");
res = transport_fetch_refs(transport, ref);
fetch_if_missing = original_fetch_if_missing;
return res;
}
static int fetch_objects(const char *remote_name,
const struct object_id *oids,
int oid_nr)
{
struct ref *ref = NULL;
int i;
for (i = 0; i < oid_nr; i++) {
struct ref *new_ref = alloc_ref(oid_to_hex(&oids[i]));
oidcpy(&new_ref->old_oid, &oids[i]);
new_ref->exact_oid = 1;
new_ref->next = ref;
ref = new_ref;
}
return fetch_refs(remote_name, ref);
}
static struct promisor_remote *promisors;
static struct promisor_remote **promisors_tail = &promisors;
static struct promisor_remote *promisor_remote_new(const char *remote_name)
{
struct promisor_remote *r;
if (*remote_name == '/') {
warning(_("promisor remote name cannot begin with '/': %s"),
remote_name);
return NULL;
}
FLEX_ALLOC_STR(r, name, remote_name);
*promisors_tail = r;
promisors_tail = &r->next;
return r;
}
static struct promisor_remote *promisor_remote_lookup(const char *remote_name,
struct promisor_remote **previous)
{
struct promisor_remote *r, *p;
for (p = NULL, r = promisors; r; p = r, r = r->next)
if (!strcmp(r->name, remote_name)) {
if (previous)
*previous = p;
return r;
}
return NULL;
}
static void promisor_remote_move_to_tail(struct promisor_remote *r,
struct promisor_remote *previous)
{
if (r->next == NULL)
return;
if (previous)
previous->next = r->next;
else
promisors = r->next ? r->next : r;
r->next = NULL;
*promisors_tail = r;
promisors_tail = &r->next;
}
static int promisor_remote_config(const char *var, const char *value, void *data)
{
const char *name;
int namelen;
const char *subkey;
if (!strcmp(var, "core.partialclonefilter"))
return git_config_string(&core_partial_clone_filter_default,
var, value);
if (parse_config_key(var, "remote", &name, &namelen, &subkey) < 0)
return 0;
if (!strcmp(subkey, "promisor")) {
char *remote_name;
if (!git_config_bool(var, value))
return 0;
remote_name = xmemdupz(name, namelen);
if (!promisor_remote_lookup(remote_name, NULL))
promisor_remote_new(remote_name);
free(remote_name);
return 0;
}
if (!strcmp(subkey, "partialclonefilter")) {
struct promisor_remote *r;
char *remote_name = xmemdupz(name, namelen);
r = promisor_remote_lookup(remote_name, NULL);
if (!r)
r = promisor_remote_new(remote_name);
free(remote_name);
if (!r)
return 0;
return git_config_string(&r->partial_clone_filter, var, value);
}
return 0;
}
static int initialized;
static void promisor_remote_init(void)
{
if (initialized)
return;
initialized = 1;
git_config(promisor_remote_config, NULL);
if (repository_format_partial_clone) {
struct promisor_remote *o, *previous;
o = promisor_remote_lookup(repository_format_partial_clone,
&previous);
if (o)
promisor_remote_move_to_tail(o, previous);
else
promisor_remote_new(repository_format_partial_clone);
}
}
static void promisor_remote_clear(void)
{
while (promisors) {
struct promisor_remote *r = promisors;
promisors = promisors->next;
free(r);
}
promisors_tail = &promisors;
}
void promisor_remote_reinit(void)
{
initialized = 0;
promisor_remote_clear();
promisor_remote_init();
}
struct promisor_remote *promisor_remote_find(const char *remote_name)
{
promisor_remote_init();
if (!remote_name)
return promisors;
return promisor_remote_lookup(remote_name, NULL);
}
int has_promisor_remote(void)
{
return !!promisor_remote_find(NULL);
}
static int remove_fetched_oids(struct repository *repo,
struct object_id **oids,
int oid_nr, int to_free)
{
int i, remaining_nr = 0;
int *remaining = xcalloc(oid_nr, sizeof(*remaining));
struct object_id *old_oids = *oids;
struct object_id *new_oids;
for (i = 0; i < oid_nr; i++)
if (oid_object_info_extended(repo, &old_oids[i], NULL,
OBJECT_INFO_SKIP_FETCH_OBJECT)) {
remaining[i] = 1;
remaining_nr++;
}
if (remaining_nr) {
int j = 0;
new_oids = xcalloc(remaining_nr, sizeof(*new_oids));
for (i = 0; i < oid_nr; i++)
if (remaining[i])
oidcpy(&new_oids[j++], &old_oids[i]);
*oids = new_oids;
if (to_free)
free(old_oids);
}
free(remaining);
return remaining_nr;
}
int promisor_remote_get_direct(struct repository *repo,
const struct object_id *oids,
int oid_nr)
{
struct promisor_remote *r;
struct object_id *remaining_oids = (struct object_id *)oids;
int remaining_nr = oid_nr;
int to_free = 0;
int res = -1;
promisor_remote_init();
for (r = promisors; r; r = r->next) {
if (fetch_objects(r->name, remaining_oids, remaining_nr) < 0) {
if (remaining_nr == 1)
continue;
remaining_nr = remove_fetched_oids(repo, &remaining_oids,
remaining_nr, to_free);
if (remaining_nr) {
to_free = 1;
continue;
}
}
res = 0;
break;
}
if (to_free)
free(remaining_oids);
return res;
}