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ap: Delay ap_free if called inside event handler

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ap.c has been mostly careful to call the event handler at the end of any
externally called function to allow methods like ap_free() to be called
within the handler, but that isn't enough.  For example in
ap_del_station we may end up emitting two events: STATION_REMOVED and
DHCP_LEASE_EXPIRED.  Use a slightly more complicated mechanism to
explicitly guard ap_free calls inside the event handler.

To make it easier, simplify cleanup in ap_assoc_reassoc with the use of
_auto_.

In ap_del_station reorder the actions to send the STATION_REMOVED event
first as the DHCP_LEASE_EXPIRED is a consequence of the former and it
makes sense for the handler to react to it first.
This commit is contained in:
Andrew Zaborowski 2021-11-08 12:28:36 +01:00 committed by Denis Kenzior
parent d9cd657135
commit c473290b47
1 changed files with 80 additions and 45 deletions
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117
src/ap.c
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@ -101,6 +101,8 @@ struct ap_state {
bool started : 1;
bool gtk_set : 1;
bool netconfig_set_addr4 : 1;
bool in_event : 1;
bool free_pending : 1;
};
struct sta_state {
@ -250,6 +252,35 @@ static void ap_reset(struct ap_state *ap)
}
}
static bool ap_event_done(struct ap_state *ap, bool prev_in_event)
{
ap->in_event = prev_in_event;
if (!prev_in_event && ap->free_pending) {
ap_free(ap);
return true;
}
return ap->free_pending;
}
/*
* Returns true if the AP is considered freed and the caller must avoid
* accessing @ap.
*/
static bool ap_event(struct ap_state *ap, enum ap_event_type event,
const void *event_data)
{
bool prev = ap->in_event;
if (ap->free_pending)
return true;
ap->in_event = true;
ap->ops->handle_event(event, event_data, ap->user_data);
return ap_event_done(ap, prev);
}
static void ap_del_station(struct sta_state *sta, uint16_t reason,
bool disassociate)
{
@ -283,6 +314,14 @@ static void ap_del_station(struct sta_state *sta, uint16_t reason,
ap_stop_handshake(sta);
/*
* If the event handler tears the AP down, we've made sure above that
* a subsequent ap_sta_free(sta) has no need to access sta->ap.
*/
if (send_event)
if (ap_event(ap, AP_EVENT_STATION_REMOVED, &event_data))
return;
/*
* Expire any DHCP leases owned by this client when it disconnects to
* make it harder for somebody to DoS the IP pool. If the client
@ -290,17 +329,20 @@ static void ap_del_station(struct sta_state *sta, uint16_t reason,
* will get their IP back.
*/
if (ap->netconfig_dhcp) {
sta->ip_alloc_lease = NULL;
l_dhcp_server_expire_by_mac(ap->netconfig_dhcp, sta->addr);
}
bool prev = ap->in_event;
/*
* If the event handler tears the AP down, we've made sure above that
* a subsequent ap_sta_free(sta) has no need to access sta->ap.
* If the LEASE_EXPIRED event in ap_dhcp_event_cb triggers an
* ap_free(), delay cleanup to avoid destroying the DHCP
* server midway through l_dhcp_server_expire_by_mac().
*/
if (send_event)
ap->ops->handle_event(AP_EVENT_STATION_REMOVED, &event_data,
ap->user_data);
ap->in_event = true;
sta->ip_alloc_lease = NULL;
l_dhcp_server_expire_by_mac(ap->netconfig_dhcp, sta->addr);
ap_event_done(ap, prev);
}
}
static bool ap_sta_match_addr(const void *a, const void *b)
@ -335,19 +377,16 @@ static void ap_del_key_cb(struct l_genl_msg *msg, void *user_data)
static void ap_new_rsna(struct sta_state *sta)
{
struct ap_state *ap = sta->ap;
struct ap_event_station_added_data event_data = {};
l_debug("STA "MAC" authenticated", MAC_STR(sta->addr));
sta->rsna = true;
if (ap->ops->handle_event) {
struct ap_event_station_added_data event_data = {};
event_data.mac = sta->addr;
event_data.assoc_ies = sta->assoc_ies;
event_data.assoc_ies_len = sta->assoc_ies_len;
ap->ops->handle_event(AP_EVENT_STATION_ADDED, &event_data,
ap->user_data);
}
ap_event(ap, AP_EVENT_STATION_ADDED, &event_data);
}
static void ap_drop_rsna(struct sta_state *sta)
@ -356,6 +395,7 @@ static void ap_drop_rsna(struct sta_state *sta)
struct l_genl_msg *msg;
uint32_t ifindex = netdev_get_ifindex(sta->ap->netdev);
uint8_t key_id = 0;
struct ap_event_station_removed_data event_data = {};
sta->rsna = false;
@ -380,12 +420,8 @@ static void ap_drop_rsna(struct sta_state *sta)
ap_stop_handshake(sta);
if (ap->ops->handle_event) {
struct ap_event_station_removed_data event_data = {};
event_data.mac = sta->addr;
ap->ops->handle_event(AP_EVENT_STATION_REMOVED, &event_data,
ap->user_data);
}
ap_event(ap, AP_EVENT_STATION_REMOVED, &event_data);
}
static void ap_set_rsn_info(struct ap_state *ap, struct ie_rsn_info *rsn)
@ -405,7 +441,7 @@ static void ap_wsc_exit_pbc(struct ap_state *ap)
ap->wsc_dpid = 0;
ap_update_beacon(ap);
ap->ops->handle_event(AP_EVENT_PBC_MODE_EXIT, NULL, ap->user_data);
ap_event(ap, AP_EVENT_PBC_MODE_EXIT, NULL);
}
struct ap_pbc_record_expiry_data {
@ -1090,9 +1126,7 @@ static void ap_wsc_handshake_event(struct handshake_state *hs,
&expiry_data);
event_data.mac = sta->addr;
sta->ap->ops->handle_event(AP_EVENT_REGISTRATION_SUCCESS,
&event_data,
sta->ap->user_data);
ap_event(sta->ap, AP_EVENT_REGISTRATION_SUCCESS, &event_data);
break;
default:
break;
@ -1594,11 +1628,11 @@ static void ap_assoc_reassoc(struct sta_state *sta, bool reassoc,
const char *ssid = NULL;
const uint8_t *rsn = NULL;
size_t ssid_len = 0;
struct l_uintset *rates = NULL;
_auto_(l_uintset_free) struct l_uintset *rates = NULL;
struct ie_rsn_info rsn_info;
int err;
struct ie_tlv_iter iter;
uint8_t *wsc_data = NULL;
_auto_(l_free) uint8_t *wsc_data = NULL;
ssize_t wsc_data_len;
bool fils_ip_req = false;
struct ie_fils_ip_addr_request_info fils_ip_req_info;
@ -1685,9 +1719,6 @@ static void ap_assoc_reassoc(struct sta_state *sta, bool reassoc,
goto bad_frame;
}
l_free(wsc_data);
wsc_data = NULL;
if (wsc_req.request_type !=
WSC_REQUEST_TYPE_ENROLLEE_OPEN_8021X) {
err = MMPDU_REASON_CODE_INVALID_IE;
@ -1728,8 +1759,9 @@ static void ap_assoc_reassoc(struct sta_state *sta, bool reassoc,
event_data.mac = sta->addr;
event_data.assoc_ies = ies;
event_data.assoc_ies_len = ies_len;
ap->ops->handle_event(AP_EVENT_REGISTRATION_START, &event_data,
ap->user_data);
if (ap_event(ap, AP_EVENT_REGISTRATION_START, &event_data))
return;
/*
* Since we're starting the PBC Registration Protocol
@ -1781,7 +1813,7 @@ static void ap_assoc_reassoc(struct sta_state *sta, bool reassoc,
if (sta->rates)
l_uintset_free(sta->rates);
sta->rates = rates;
sta->rates = l_steal_ptr(rates);
l_free(sta->assoc_ies);
@ -1823,11 +1855,6 @@ bad_frame:
else if (sta->associated)
ap_stop_handshake(sta);
if (rates)
l_uintset_free(rates);
l_free(wsc_data);
if (!ap_assoc_resp(ap, sta, sta->addr, err, reassoc,
req, (void *) ies + ies_len - (void *) req,
NULL, ap_fail_assoc_resp_cb))
@ -2209,6 +2236,7 @@ static void ap_start_failed(struct ap_state *ap, int err)
{
struct ap_event_start_failed_data data = { err };
ap->in_event = true;
ap->ops->handle_event(AP_EVENT_START_FAILED, &data, ap->user_data);
ap_reset(ap);
l_genl_family_free(ap->nl80211);
@ -2224,13 +2252,11 @@ static void ap_dhcp_event_cb(struct l_dhcp_server *server,
switch (event) {
case L_DHCP_SERVER_EVENT_NEW_LEASE:
ap->ops->handle_event(AP_EVENT_DHCP_NEW_LEASE, lease,
ap->user_data);
ap_event(ap, AP_EVENT_DHCP_NEW_LEASE, lease);
break;
case L_DHCP_SERVER_EVENT_LEASE_EXPIRED:
ap->ops->handle_event(AP_EVENT_DHCP_LEASE_EXPIRED, lease,
ap->user_data);
ap_event(ap, AP_EVENT_DHCP_LEASE_EXPIRED, lease);
break;
default:
@ -2267,7 +2293,7 @@ static void ap_start_cb(struct l_genl_msg *msg, void *user_data)
}
ap->started = true;
ap->ops->handle_event(AP_EVENT_STARTED, NULL, ap->user_data);
ap_event(ap, AP_EVENT_STARTED, NULL);
}
static struct l_genl_msg *ap_build_cmd_start_ap(struct ap_state *ap)
@ -2552,6 +2578,8 @@ static void ap_mlme_notify(struct l_genl_msg *msg, void *user_data)
switch (l_genl_msg_get_command(msg)) {
case NL80211_CMD_STOP_AP:
ap->in_event = true;
if (ap->start_stop_cmd_id) {
struct ap_event_start_failed_data data = { -ECANCELED };
@ -3304,7 +3332,9 @@ void ap_shutdown(struct ap_state *ap, ap_stopped_func_t stopped_func,
if (ap->started) {
ap->started = false;
ap->ops->handle_event(AP_EVENT_STOPPING, NULL, ap->user_data);
if (ap_event(ap, AP_EVENT_STOPPING, NULL))
return;
}
ap_reset(ap);
@ -3355,6 +3385,11 @@ free_ap:
/* Free @ap without a graceful shutdown */
void ap_free(struct ap_state *ap)
{
if (ap->in_event) {
ap->free_pending = true;
return;
}
ap_reset(ap);
l_genl_family_free(ap->nl80211);
l_free(ap);