nl80211_pmsr_start() assigns the request cookie, calls the driver's ->start_pmsr() callback, and only then adds the request to wdev->pmsr_list, without holding pmsr_lock for the addition. mac80211_hwsim saves the request in its start callback and returns. Since nl80211 uses parallel_ops, an immediate REPORT_PMSR can then run before nl80211_pmsr_start() reaches its post-start list_add_tail(). hwsim also dispatches reports from its virtio receive workqueue. Completion removes the request from wdev->pmsr_list under pmsr_lock and frees it. Thus completion can precede publication, race the unlocked list mutation, or free the request before nl80211_pmsr_start() reads req->cookie for the netlink reply. Add the request to wdev->pmsr_list under pmsr_lock before calling the driver, and use a cookie value saved before the call so the request is not dereferenced after a successful start. On an error return the driver has not retained or completed the request, so remove it from the list under the lock and free it. Fixes: 9bb7e0f24e7e ("cfg80211: add peer measurement with FTM initiator API") Link: https://lore.kernel.org/all/20260723010916.76433-1-enderaoelyther@gmail.com/ Assisted-by: Codex:gpt-5 Assisted-by: Claude:opus-4.8 Signed-off-by: Zhao Li --- Changes in v2: - Drop callback documentation that implied synchronous completion was supported. - Reword the local comment as defensive handling for races or broken drivers that complete the request before ->start_pmsr() returns. --- net/wireless/pmsr.c | 22 ++++++++++++++++++---- 1 file changed, 18 insertions(+), 4 deletions(-) diff --git a/net/wireless/pmsr.c b/net/wireless/pmsr.c index d1e2fae5bc0e..97449bcb9a22 100644 --- a/net/wireless/pmsr.c +++ b/net/wireless/pmsr.c @@ -420,6 +420,7 @@ int nl80211_pmsr_start(struct sk_buff *skb, struct genl_info *info) const struct cfg80211_pmsr_capabilities *capa; struct cfg80211_pmsr_request *req; struct nlattr *peers, *peer; + u64 cookie; capa = rdev->wiphy.pmsr_capa; @@ -521,14 +522,27 @@ int nl80211_pmsr_start(struct sk_buff *skb, struct genl_info *info) } req->cookie = cfg80211_assign_cookie(rdev); req->nl_portid = info->snd_portid; + cookie = req->cookie; + + /* + * Add to the list before the driver call; under races or broken + * drivers, completion may free the request before rdev_start_pmsr() + * returns. Use the saved cookie below. + */ + spin_lock_bh(&wdev->pmsr_lock); + list_add_tail(&req->list, &wdev->pmsr_list); + spin_unlock_bh(&wdev->pmsr_lock); err = rdev_start_pmsr(rdev, wdev, req); - if (err) + if (err) { + /* An error return leaves the request owned by this path. */ + spin_lock_bh(&wdev->pmsr_lock); + list_del(&req->list); + spin_unlock_bh(&wdev->pmsr_lock); goto out_err; + } - list_add_tail(&req->list, &wdev->pmsr_list); - - nl_set_extack_cookie_u64(info->extack, req->cookie); + nl_set_extack_cookie_u64(info->extack, cookie); return 0; out_err: kfree(req); -- 2.50.1 (Apple Git-155)