On 06/07/2018 04:59 PM, Cong Wang wrote:
On Thu, Jun 7, 2018 at 4:48 PM, <greearb@xxxxxxxxxxxxxxx> wrote:diff --git a/include/net/fq_impl.h b/include/net/fq_impl.h index be7c0fa..cb911f0 100644 --- a/include/net/fq_impl.h +++ b/include/net/fq_impl.h @@ -78,7 +78,10 @@ static struct sk_buff *fq_tin_dequeue(struct fq *fq, return NULL; } - flow = list_first_entry(head, struct fq_flow, flowchain); + flow = list_first_entry_or_null(head, struct fq_flow, flowchain); + + if (WARN_ON_ONCE(!flow)) + return NULL;This does not make sense either. list_first_entry_or_null() returns NULL only when the list is empty, but we already check list_empty() right before this code, and it is protected by fq->lock.
Hello Michal, git blame shows you as the author of the fq_impl.h code. I saw a crash when debugging funky ath10k firmware in a 4.16 + hacks kernel. There was an apparent mostly-null deref in the fq_tin_dequeue method. According to gdb, it was within 1 line of the dereference of 'flow'. My hack above is probably not that useful. Cong thinks maybe the locking is bad. If you get a chance, please review this thread and see if you have any ideas for a better fix (or better debugging code). As always, if you would like me to generate you a buggy firmware that will crash in the tx path and cause all sorts of mayhem in the ath10k driver and wifi stack, I will be happy to do so. https://www.mail-archive.com/netdev@xxxxxxxxxxxxxxx/msg239738.html Thanks, Ben -- Ben Greear <greearb@xxxxxxxxxxxxxxx> Candela Technologies Inc http://www.candelatech.com
