wifi: mac80211: fix initialization of rx->link and rx->link_sta

There are some codepaths that do not initialize rx->link_sta properly. This
causes a crash in places which assume that rx->link_sta is valid if rx->sta
is valid.
One known instance is triggered by __ieee80211_rx_h_amsdu being called from
fast-rx. It results in a crash like this one:

 BUG: kernel NULL pointer dereference, address: 00000000000000a8
 #PF: supervisor write access in kernel mode
 #PF: error_code(0x0002) - not-present page PGD 0 P4D 0
 Oops: 0002 [#1] PREEMPT SMP PTI
 CPU: 1 PID: 506 Comm: mt76-usb-rx phy Tainted: G            E      6.1.0-debian64x+1.7 #3
 Hardware name: ZOTAC ZBOX-ID92/ZBOX-IQ01/ZBOX-ID92/ZBOX-IQ01, BIOS B220P007 05/21/2014
 RIP: 0010:ieee80211_deliver_skb+0x62/0x1f0 [mac80211]
 Code: 00 48 89 04 24 e8 9e a7 c3 df 89 c0 48 03 1c c5 a0 ea 39 a1 4c 01 6b 08 48 ff 03 48
       83 7d 28 00 74 11 48 8b 45 30 48 63 55 44 <48> 83 84 d0 a8 00 00 00 01 41 8b 86 c0
       11 00 00 8d 50 fd 83 fa 01
 RSP: 0018:ffff999040803b10 EFLAGS: 00010286
 RAX: 0000000000000000 RBX: ffffb9903f496480 RCX: 0000000000000000
 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
 RBP: ffff999040803ce0 R08: 0000000000000000 R09: 0000000000000000
 R10: 0000000000000000 R11: 0000000000000000 R12: ffff8d21828ac900
 R13: 000000000000004a R14: ffff8d2198ed89c0 R15: ffff8d2198ed8000
 FS:  0000000000000000(0000) GS:ffff8d24afe80000(0000) knlGS:0000000000000000
 CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
 CR2: 00000000000000a8 CR3: 0000000429810002 CR4: 00000000001706e0
 Call Trace:
  <TASK>
  __ieee80211_rx_h_amsdu+0x1b5/0x240 [mac80211]
  ? ieee80211_prepare_and_rx_handle+0xcdd/0x1320 [mac80211]
  ? __local_bh_enable_ip+0x3b/0xa0
  ieee80211_prepare_and_rx_handle+0xcdd/0x1320 [mac80211]
  ? prepare_transfer+0x109/0x1a0 [xhci_hcd]
  ieee80211_rx_list+0xa80/0xda0 [mac80211]
  mt76_rx_complete+0x207/0x2e0 [mt76]
  mt76_rx_poll_complete+0x357/0x5a0 [mt76]
  mt76u_rx_worker+0x4f5/0x600 [mt76_usb]
  ? mt76_get_min_avg_rssi+0x140/0x140 [mt76]
  __mt76_worker_fn+0x50/0x80 [mt76]
  kthread+0xed/0x120
  ? kthread_complete_and_exit+0x20/0x20
  ret_from_fork+0x22/0x30

Since the initialization of rx->link and rx->link_sta is rather convoluted
and duplicated in many places, clean it up by using a helper function to
set it.

Fixes: ccdde7c74ffd ("wifi: mac80211: properly implement MLO key handling")
Fixes: b320d6c456ff ("wifi: mac80211: use correct rx link_sta instead of default")
Signed-off-by: Felix Fietkau <nbd@nbd.name>
Link: https://lore.kernel.org/r/20221230200747.19040-1-nbd@nbd.name
[remove unnecessary rx->sta->sta.mlo check]
Cc: stable@vger.kernel.org
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

diff --git a/net/mac80211/rx.c b/net/mac80211/rx.c
index 7e3ab6e1b28f3d5c4547e97fbbabc42a2e83adbc..c518287b2356bdcee35ae6486fbcbbfb2fbbf82d 100644 (file)
--- a/net/mac80211/rx.c
+++ b/net/mac80211/rx.c
@@ -4049,6 +4049,58 @@ static void ieee80211_invoke_rx_handlers(struct ieee80211_rx_data *rx)
 #undef CALL_RXH
 }
 
+static bool
+ieee80211_rx_is_valid_sta_link_id(struct ieee80211_sta *sta, u8 link_id)
+{
+       if (!sta->mlo)
+               return false;
+
+       return !!(sta->valid_links & BIT(link_id));
+}
+
+static bool ieee80211_rx_data_set_link(struct ieee80211_rx_data *rx,
+                                      u8 link_id)
+{
+       rx->link_id = link_id;
+       rx->link = rcu_dereference(rx->sdata->link[link_id]);
+
+       if (!rx->sta)
+               return rx->link;
+
+       if (!ieee80211_rx_is_valid_sta_link_id(&rx->sta->sta, link_id))
+               return false;
+
+       rx->link_sta = rcu_dereference(rx->sta->link[link_id]);
+
+       return rx->link && rx->link_sta;
+}
+
+static bool ieee80211_rx_data_set_sta(struct ieee80211_rx_data *rx,
+                                     struct ieee80211_sta *pubsta,
+                                     int link_id)
+{
+       struct sta_info *sta;
+
+       sta = container_of(pubsta, struct sta_info, sta);
+
+       rx->link_id = link_id;
+       rx->sta = sta;
+
+       if (sta) {
+               rx->local = sta->sdata->local;
+               if (!rx->sdata)
+                       rx->sdata = sta->sdata;
+               rx->link_sta = &sta->deflink;
+       }
+
+       if (link_id < 0)
+               rx->link = &rx->sdata->deflink;
+       else if (!ieee80211_rx_data_set_link(rx, link_id))
+               return false;
+
+       return true;
+}
+
 /*
  * This function makes calls into the RX path, therefore
  * it has to be invoked under RCU read lock.
@@ -4057,16 +4109,19 @@ void ieee80211_release_reorder_timeout(struct sta_info *sta, int tid)
 {
        struct sk_buff_head frames;
        struct ieee80211_rx_data rx = {
-               .sta = sta,
-               .sdata = sta->sdata,
-               .local = sta->local,
                /* This is OK -- must be QoS data frame */
                .security_idx = tid,
                .seqno_idx = tid,
-               .link_id = -1,
        };
        struct tid_ampdu_rx *tid_agg_rx;
-       u8 link_id;
+       int link_id = -1;
+
+       /* FIXME: statistics won't be right with this */
+       if (sta->sta.valid_links)
+               link_id = ffs(sta->sta.valid_links) - 1;
+
+       if (!ieee80211_rx_data_set_sta(&rx, &sta->sta, link_id))
+               return;
 
        tid_agg_rx = rcu_dereference(sta->ampdu_mlme.tid_rx[tid]);
        if (!tid_agg_rx)
@@ -4086,10 +4141,6 @@ void ieee80211_release_reorder_timeout(struct sta_info *sta, int tid)
                };
                drv_event_callback(rx.local, rx.sdata, &event);
        }
-       /* FIXME: statistics won't be right with this */
-       link_id = sta->sta.valid_links ? ffs(sta->sta.valid_links) - 1 : 0;
-       rx.link = rcu_dereference(sta->sdata->link[link_id]);
-       rx.link_sta = rcu_dereference(sta->link[link_id]);
 
        ieee80211_rx_handlers(&rx, &frames);
 }
@@ -4105,7 +4156,6 @@ void ieee80211_mark_rx_ba_filtered_frames(struct ieee80211_sta *pubsta, u8 tid,
                /* This is OK -- must be QoS data frame */
                .security_idx = tid,
                .seqno_idx = tid,
-               .link_id = -1,
        };
        int i, diff;
 
@@ -4116,10 +4166,8 @@ void ieee80211_mark_rx_ba_filtered_frames(struct ieee80211_sta *pubsta, u8 tid,
 
        sta = container_of(pubsta, struct sta_info, sta);
 
-       rx.sta = sta;
-       rx.sdata = sta->sdata;
-       rx.link = &rx.sdata->deflink;
-       rx.local = sta->local;
+       if (!ieee80211_rx_data_set_sta(&rx, pubsta, -1))
+               return;
 
        rcu_read_lock();
        tid_agg_rx = rcu_dereference(sta->ampdu_mlme.tid_rx[tid]);
@@ -4506,15 +4554,6 @@ void ieee80211_check_fast_rx_iface(struct ieee80211_sub_if_data *sdata)
        mutex_unlock(&local->sta_mtx);
 }
 
-static bool
-ieee80211_rx_is_valid_sta_link_id(struct ieee80211_sta *sta, u8 link_id)
-{
-       if (!sta->mlo)
-               return false;
-
-       return !!(sta->valid_links & BIT(link_id));
-}
-
 static void ieee80211_rx_8023(struct ieee80211_rx_data *rx,
                              struct ieee80211_fast_rx *fast_rx,
                              int orig_len)
@@ -4625,7 +4664,6 @@ static bool ieee80211_invoke_fast_rx(struct ieee80211_rx_data *rx,
        struct sk_buff *skb = rx->skb;
        struct ieee80211_hdr *hdr = (void *)skb->data;
        struct ieee80211_rx_status *status = IEEE80211_SKB_RXCB(skb);
-       struct sta_info *sta = rx->sta;
        int orig_len = skb->len;
        int hdrlen = ieee80211_hdrlen(hdr->frame_control);
        int snap_offs = hdrlen;
@@ -4637,7 +4675,6 @@ static bool ieee80211_invoke_fast_rx(struct ieee80211_rx_data *rx,
                u8 da[ETH_ALEN];
                u8 sa[ETH_ALEN];
        } addrs __aligned(2);
-       struct link_sta_info *link_sta;
        struct ieee80211_sta_rx_stats *stats;
 
        /* for parallel-rx, we need to have DUP_VALIDATED, otherwise we write
@@ -4740,18 +4777,10 @@ static bool ieee80211_invoke_fast_rx(struct ieee80211_rx_data *rx,
  drop:
        dev_kfree_skb(skb);
 
-       if (rx->link_id >= 0) {
-               link_sta = rcu_dereference(sta->link[rx->link_id]);
-               if (!link_sta)
-                       return true;
-       } else {
-               link_sta = &sta->deflink;
-       }
-
        if (fast_rx->uses_rss)
-               stats = this_cpu_ptr(link_sta->pcpu_rx_stats);
+               stats = this_cpu_ptr(rx->link_sta->pcpu_rx_stats);
        else
-               stats = &link_sta->rx_stats;
+               stats = &rx->link_sta->rx_stats;
 
        stats->dropped++;
        return true;
@@ -4769,8 +4798,8 @@ static bool ieee80211_prepare_and_rx_handle(struct ieee80211_rx_data *rx,
        struct ieee80211_local *local = rx->local;
        struct ieee80211_sub_if_data *sdata = rx->sdata;
        struct ieee80211_hdr *hdr = (void *)skb->data;
-       struct link_sta_info *link_sta = NULL;
-       struct ieee80211_link_data *link;
+       struct link_sta_info *link_sta = rx->link_sta;
+       struct ieee80211_link_data *link = rx->link;
 
        rx->skb = skb;
 
@@ -4792,35 +4821,6 @@ static bool ieee80211_prepare_and_rx_handle(struct ieee80211_rx_data *rx,
        if (!ieee80211_accept_frame(rx))
                return false;
 
-       if (rx->link_id >= 0) {
-               link = rcu_dereference(rx->sdata->link[rx->link_id]);
-
-               /* we might race link removal */
-               if (!link)
-                       return true;
-               rx->link = link;
-
-               if (rx->sta) {
-                       rx->link_sta =
-                               rcu_dereference(rx->sta->link[rx->link_id]);
-                       if (!rx->link_sta)
-                               return true;
-               }
-       } else {
-               if (rx->sta)
-                       rx->link_sta = &rx->sta->deflink;
-
-               rx->link = &sdata->deflink;
-       }
-
-       if (unlikely(!is_multicast_ether_addr(hdr->addr1) &&
-                    rx->link_id >= 0 && rx->sta && rx->sta->sta.mlo)) {
-               link_sta = rcu_dereference(rx->sta->link[rx->link_id]);
-
-               if (WARN_ON_ONCE(!link_sta))
-                       return true;
-       }
-
        if (!consume) {
                struct skb_shared_hwtstamps *shwt;
 
@@ -4840,7 +4840,7 @@ static bool ieee80211_prepare_and_rx_handle(struct ieee80211_rx_data *rx,
                shwt->hwtstamp = skb_hwtstamps(skb)->hwtstamp;
        }
 
-       if (unlikely(link_sta)) {
+       if (unlikely(rx->sta && rx->sta->sta.mlo)) {
                /* translate to MLD addresses */
                if (ether_addr_equal(link->conf->addr, hdr->addr1))
                        ether_addr_copy(hdr->addr1, rx->sdata->vif.addr);
@@ -4870,6 +4870,7 @@ static void __ieee80211_rx_handle_8023(struct ieee80211_hw *hw,
        struct ieee80211_rx_status *status = IEEE80211_SKB_RXCB(skb);
        struct ieee80211_fast_rx *fast_rx;
        struct ieee80211_rx_data rx;
+       int link_id = -1;
 
        memset(&rx, 0, sizeof(rx));
        rx.skb = skb;
@@ -4886,12 +4887,8 @@ static void __ieee80211_rx_handle_8023(struct ieee80211_hw *hw,
        if (!pubsta)
                goto drop;
 
-       rx.sta = container_of(pubsta, struct sta_info, sta);
-       rx.sdata = rx.sta->sdata;
-
-       if (status->link_valid &&
-           !ieee80211_rx_is_valid_sta_link_id(pubsta, status->link_id))
-               goto drop;
+       if (status->link_valid)
+               link_id = status->link_id;
 
        /*
         * TODO: Should the frame be dropped if the right link_id is not
@@ -4900,19 +4897,8 @@ static void __ieee80211_rx_handle_8023(struct ieee80211_hw *hw,
         * link_id is used only for stats purpose and updating the stats on
         * the deflink is fine?
         */
-       if (status->link_valid)
-               rx.link_id = status->link_id;
-
-       if (rx.link_id >= 0) {
-               struct ieee80211_link_data *link;
-
-               link =  rcu_dereference(rx.sdata->link[rx.link_id]);
-               if (!link)
-                       goto drop;
-               rx.link = link;
-       } else {
-               rx.link = &rx.sdata->deflink;
-       }
+       if (!ieee80211_rx_data_set_sta(&rx, pubsta, link_id))
+               goto drop;
 
        fast_rx = rcu_dereference(rx.sta->fast_rx);
        if (!fast_rx)
@@ -4930,6 +4916,8 @@ static bool ieee80211_rx_for_interface(struct ieee80211_rx_data *rx,
 {
        struct link_sta_info *link_sta;
        struct ieee80211_hdr *hdr = (void *)skb->data;
+       struct sta_info *sta;
+       int link_id = -1;
 
        /*
         * Look up link station first, in case there's a
@@ -4939,24 +4927,19 @@ static bool ieee80211_rx_for_interface(struct ieee80211_rx_data *rx,
         */
        link_sta = link_sta_info_get_bss(rx->sdata, hdr->addr2);
        if (link_sta) {
-               rx->sta = link_sta->sta;
-               rx->link_id = link_sta->link_id;
+               sta = link_sta->sta;
+               link_id = link_sta->link_id;
        } else {
                struct ieee80211_rx_status *status = IEEE80211_SKB_RXCB(skb);
 
-               rx->sta = sta_info_get_bss(rx->sdata, hdr->addr2);
-               if (rx->sta) {
-                       if (status->link_valid &&
-                           !ieee80211_rx_is_valid_sta_link_id(&rx->sta->sta,
-                                                              status->link_id))
-                               return false;
-
-                       rx->link_id = status->link_valid ? status->link_id : -1;
-               } else {
-                       rx->link_id = -1;
-               }
+               sta = sta_info_get_bss(rx->sdata, hdr->addr2);
+               if (status->link_valid)
+                       link_id = status->link_id;
        }
 
+       if (!ieee80211_rx_data_set_sta(rx, &sta->sta, link_id))
+               return false;
+
        return ieee80211_prepare_and_rx_handle(rx, skb, consume);
 }
 
@@ -5015,19 +4998,15 @@ static void __ieee80211_rx_handle_packet(struct ieee80211_hw *hw,
 
        if (ieee80211_is_data(fc)) {
                struct sta_info *sta, *prev_sta;
-               u8 link_id = status->link_id;
+               int link_id = -1;
 
-               if (pubsta) {
-                       rx.sta = container_of(pubsta, struct sta_info, sta);
-                       rx.sdata = rx.sta->sdata;
+               if (status->link_valid)
+                       link_id = status->link_id;
 
-                       if (status->link_valid &&
-                           !ieee80211_rx_is_valid_sta_link_id(pubsta, link_id))
+               if (pubsta) {
+                       if (!ieee80211_rx_data_set_sta(&rx, pubsta, link_id))
                                goto out;
 
-                       if (status->link_valid)
-                               rx.link_id = status->link_id;
-
                        /*
                         * In MLO connection, fetch the link_id using addr2
                         * when the driver does not pass link_id in status.
@@ -5045,7 +5024,7 @@ static void __ieee80211_rx_handle_packet(struct ieee80211_hw *hw,
                                if (!link_sta)
                                        goto out;
 
-                               rx.link_id = link_sta->link_id;
+                               ieee80211_rx_data_set_link(&rx, link_sta->link_id);
                        }
 
                        if (ieee80211_prepare_and_rx_handle(&rx, skb, true))
@@ -5061,30 +5040,27 @@ static void __ieee80211_rx_handle_packet(struct ieee80211_hw *hw,
                                continue;
                        }
 
-                       if ((status->link_valid &&
-                            !ieee80211_rx_is_valid_sta_link_id(&prev_sta->sta,
-                                                               link_id)) ||
-                           (!status->link_valid && prev_sta->sta.mlo))
+                       rx.sdata = prev_sta->sdata;
+                       if (!ieee80211_rx_data_set_sta(&rx, &prev_sta->sta,
+                                                      link_id))
+                               goto out;
+
+                       if (!status->link_valid && prev_sta->sta.mlo)
                                continue;
 
-                       rx.link_id = status->link_valid ? link_id : -1;
-                       rx.sta = prev_sta;
-                       rx.sdata = prev_sta->sdata;
                        ieee80211_prepare_and_rx_handle(&rx, skb, false);
 
                        prev_sta = sta;
                }
 
                if (prev_sta) {
-                       if ((status->link_valid &&
-                            !ieee80211_rx_is_valid_sta_link_id(&prev_sta->sta,
-                                                               link_id)) ||
-                           (!status->link_valid && prev_sta->sta.mlo))
+                       rx.sdata = prev_sta->sdata;
+                       if (!ieee80211_rx_data_set_sta(&rx, &prev_sta->sta,
+                                                      link_id))
                                goto out;
 
-                       rx.link_id = status->link_valid ? link_id : -1;
-                       rx.sta = prev_sta;
-                       rx.sdata = prev_sta->sdata;
+                       if (!status->link_valid && prev_sta->sta.mlo)
+                               goto out;
 
                        if (ieee80211_prepare_and_rx_handle(&rx, skb, true))
                                return;