wifi: cfg80211: publish PMSR request before starting the driver

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 <enderaoelyther@gmail.com>
Link: https://patch.msgid.link/20260723202223.99661-1-enderaoelyther@gmail.com
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

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