On Thu, Jun 7, 2018 at 4:48 PM, <gree...@candelatech.com> wrote: > From: Ben Greear <gree...@candelatech.com> > > While testing an ath10k firmware that often crashed under load, > I was seeing kernel crashes as well. One of them appeared to > be a dereference of a NULL flow object in fq_tin_dequeue. > > I have since fixed the firmware flaw, but I think it would be > worth adding the WARN_ON in case the problem appears again. > > BUG: unable to handle kernel NULL pointer dereference at 000000000000003c > IP: ieee80211_tx_dequeue+0xfb/0xb10 [mac80211]
Instead of adding WARN_ON(), you need to think about the locking there, it is suspicious: fq is from struct ieee80211_local: struct fq *fq = &local->fq; tin is from struct txq_info: struct fq_tin *tin = &txqi->tin; I don't know if fq and tin are supposed to be 1:1, if not there is a bug in the locking, because ->new_flows and ->old_flows are both inside tin instead of fq, but they are protected by fq->lock....
