On Tue, Mar 31, 2020 at 10:59:01AM +0800, Jason Wang wrote: > On 2020/3/31 上午12:12, Will Deacon wrote: > > When an XDP program is installed, tun_build_skb() grabs a reference to > > the current page fragment page if the program returns XDP_REDIRECT or > > XDP_TX. However, since tun_xdp_act() passes through negative return > > values from the XDP program, it is possible to trigger the error path by > > mistake and accidentally drop a reference to the fragments page without > > taking one, leading to a spurious free. This is believed to be the cause > > of some KASAN use-after-free reports from syzbot [1], although without a > > reproducer it is not possible to confirm whether this patch fixes the > > problem. > > > > Ensure that we only drop a reference to the fragments page if the XDP > > transmit or redirect operations actually fail. > > > > [1] https://syzkaller.appspot.com/bug?id=e76a6af1be4acd727ff6bbca669833f98cbf5d95 > > > I think the patch fixes the issue reported. Since I can see the warn of bad > page state in put_page(). [...] > Acked-by: Jason Wang <jasowang@xxxxxxxxxx> Thanks, Jason. In which case, I'll add this tag along with: Fixes: 8ae1aff0b331 ("tuntap: split out XDP logic") Will
