On Tue, Jan 02, 2018 at 04:35:11PM -0800, Andrei Vagin wrote: > On Tue, Jan 02, 2018 at 10:58:01AM -0800, syzbot wrote: > > Hello, > > > > syzkaller hit the following crash on > > 75aa5540627fdb3d8f86229776ea87f995275351 > > git://git.cmpxchg.org/linux-mmots.git/master > > compiler: gcc (GCC) 7.1.1 20170620 > > .config is attached > > Raw console output is attached. > > C reproducer is attached > > syzkaller reproducer is attached. See https://goo.gl/kgGztJ > > for information about syzkaller reproducers > > > > > > IMPORTANT: if you fix the bug, please add the following tag to the commit: > > Reported-by: syzbot+e432865c29eb4c48c...@syzkaller.appspotmail.com > > It will help syzbot understand when the bug is fixed. See footer for > > details. > > If you forward the report, please keep this part and the footer. > > > > netlink: 3 bytes leftover after parsing attributes in process > > `syzkaller140561'. > > netlink: 3 bytes leftover after parsing attributes in process > > `syzkaller140561'. > > netlink: 3 bytes leftover after parsing attributes in process > > `syzkaller140561'. > > kasan: CONFIG_KASAN_INLINE enabled > > kasan: GPF could be caused by NULL-ptr deref or user memory access > > general protection fault: 0000 [#1] SMP KASAN > > Dumping ftrace buffer: > > (ftrace buffer empty) > > Modules linked in: > > CPU: 1 PID: 3149 Comm: syzkaller140561 Not tainted 4.15.0-rc4-mm1+ #47 > > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS > > Google 01/01/2011 > > RIP: 0010:__netlink_ns_capable+0x8b/0x120 net/netlink/af_netlink.c:868 > > NETLINK_CB(skb).sk is NULL here. It looks like we have to use > sk_ns_capable instead of netlink_ns_capable: > > diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c > index c688dc564b11..408c75de52ea 100644 > --- a/net/core/rtnetlink.c > +++ b/net/core/rtnetlink.c > @@ -1762,7 +1762,7 @@ static struct net *get_target_net(struct sk_buff > *skb, int netnsid) > /* For now, the caller is required to have CAP_NET_ADMIN in > * the user namespace owning the target net ns. > */ > - if (!netlink_ns_capable(skb, net->user_ns, CAP_NET_ADMIN)) { > + if (!sk_ns_capable(skb->sk, net->user_ns, CAP_NET_ADMIN)) { > put_net(net); > return ERR_PTR(-EACCES); > } >
get_target_net() is used twice in the code. In rtnl_getlink(), we need to use netlink_ns_capable(skb, ...), but in rtnl_dump_ifinfo, we need to use sk_ns_capable(skb->sk, ...). Pls, take a look at this patch: https://patchwork.ozlabs.org/patch/854896/ Subject: rtnetlink: give a user socket to get_target_net()
