[PATCH] wifi: mac80211: restore dormant links when link updates fail

[Zhao Li]

A failed MLO link update can leave the interface with the requested
dormant-links bitmap instead of its previous one. This can disable active
links or trigger a bitmap warning during rollback.

The error path restores the old valid-links bitmap but passes the new
dormant_links argument to ieee80211_set_vif_links_bitmaps().

Save the old dormant bitmap before changing link state and use it when
restoring the old configuration.

LLM assistance was used to find the bug and review.

Fixes: 6d543b34dbcf ("wifi: mac80211: Support disabled links during association")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Zhao Li <enderaoelyther@xxxxxxxxx>
---
Validation: A W=1 module build with MODPOST passed on top of
the prerequisite patch. A QEMU guest forced duplicate-address rollback: the
old code cleared dormant and active links, while this change preserved
dormant=0x2 and active=0x1 without a warning. The driver-failure path was
not run. A reproducer is available on request.
Sparse C=2 passed. Targeted Smatch introduced no new diagnostics.

Depends on "wifi: mac80211: fix use-after-free when MLO link setup is
rolled back", Message-ID <20261026152654.80697-1-enderaoelyther@xxxxxxxxx>.

 net/mac80211/link.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/mac80211/link.c b/net/mac80211/link.c
index fac5a8c22596..41c1ae52e097 100644
--- a/net/mac80211/link.c
+++ b/net/mac80211/link.c
@@ -290,6 +290,7 @@ static int ieee80211_vif_update_links(struct ieee80211_sub_if_data *sdata,
 {
 	u16 old_links = sdata->vif.valid_links;
 	u16 old_active = sdata->vif.active_links;
+	u16 old_dormant = sdata->vif.dormant_links;
 	unsigned long add = new_links & ~old_links;
 	unsigned long rem = old_links & ~new_links;
 	unsigned long sta_rem = rem;
@@ -399,7 +400,7 @@ static int ieee80211_vif_update_links(struct ieee80211_sub_if_data *sdata,
 		/* restore config */
 		memcpy(sdata->link, old_data, sizeof(old_data));
 		memcpy(sdata->vif.link_conf, old, sizeof(old));
-		ieee80211_set_vif_links_bitmaps(sdata, old_links, dormant_links);
+		ieee80211_set_vif_links_bitmaps(sdata, old_links, old_dormant);
 		/* drain RCU readers before cancelling work they may queue */
 		synchronize_rcu();
 		for_each_set_bit(link_id, &add, IEEE80211_MLD_MAX_NUM_LINKS) {

base-commit: 25e73f1d6868c759c8eb56cad4e411692c5341b4
prerequisite-patch-id: f3df0cde74cce63ac37decd81c2613cdb13f49ff
-- 
2.56.0