Recently I've struggled with crashes in the xt_qtaguid netfilter module. This module is written by Google and used with Android. The match function in xt_qtaguid eventually tries to access skb->sk->sk_socket->file What I find is that the sk->sk_socket pointer is sometimes 0xAAAAAAAA, or PAGE_POISON. In fact everything after the first 16 bytes of the struct sock sk is PAGE_POISON. I've confirmed that if I change PAGE_POISON, the values I see in the sk structure change as well. I was curious how this structure was being allocated/initialized and instrumented the sk_alloc, sk_free, and sk_clone_lock functions. When xt_qtaguid encounters a bad struct sock, that sock does not show up as ever having been allocated (or freed). The struct sock is being assigned to the skb in tcb_v4_early_demux(). I modified that function immediately after the sk is assigned from __inet_lookup_established() to panic if the sk has a sk_socket pointer of PAGE_POISON. I can reproduce that condition on my target by simply attempting to mount an NFS volume. Initiating *and* aborting wget operations also reproduces the issue - simply initiating a bunch of wgets is not enough to trigger it. I have not yet been able to reproduce the bad condition when disabling ip_early_demux via the sysctl. Any possibility this is an actual issue with that feature? My target is an MSM using the ks8851 ethernet module. thanks, Steve -- The Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation -- To unsubscribe from this list: send the line "unsubscribe linux-arm-msm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
