On 2/3/25 10:57, syzbot wrote: > Hello, > > syzbot found the following issue on: > > HEAD commit: c2933b2befe2 Merge tag 'net-6.14-rc1' of git://git.kernel... > git tree: net-next > console output: https://syzkaller.appspot.com/x/log.txt?x=16f676b0580000 > kernel config: https://syzkaller.appspot.com/x/.config?x=d033b14aeef39158 > dashboard link: https://syzkaller.appspot.com/bug?extid=9d55b199192a4be7d02c > compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40 > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=13300b24580000 > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=12418518580000 > > Downloadable assets: > disk image: https://storage.googleapis.com/syzbot-assets/c7667ae12603/disk-c2933b2b.raw.xz > vmlinux: https://storage.googleapis.com/syzbot-assets/944ca63002c1/vmlinux-c2933b2b.xz > kernel image: https://storage.googleapis.com/syzbot-assets/30748115bf0b/bzImage-c2933b2b.xz > > The issue was bisected to: > > commit fcdd2242c0231032fc84e1404315c245ae56322a > Author: Michal Luczaj <mhal@xxxxxxx> > Date: Tue Jan 28 13:15:27 2025 +0000 > > vsock: Keep the binding until socket destruction syzbot is correct (thanks), bisected commit introduced a regression. sock_orphan(sk) is being called without taking into consideration that it does `sk->sk_wq = NULL`. Later, if SO_LINGER is set, sk->sk_wq gets dereferenced in virtio_transport_wait_close(). Repro, as shown by syzbot, is simply from socket import * lis = socket(AF_VSOCK, SOCK_STREAM) lis.bind((1, 1234)) # VMADDR_CID_LOCAL lis.listen() s = socket(AF_VSOCK, SOCK_STREAM) s.setsockopt(SOL_SOCKET, SO_LINGER, (1<<32) | 1) s.connect(lis.getsockname()) s.close() A way of fixing this is to put sock_orphan(sk) back where it was before the breaking patch and instead explicitly flip just the SOCK_DEAD bit, i.e. diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c index 075695173648..06250bb9afe2 100644 --- a/net/vmw_vsock/af_vsock.c +++ b/net/vmw_vsock/af_vsock.c @@ -824,13 +824,14 @@ static void __vsock_release(struct sock *sk, int level) */ lock_sock_nested(sk, level); - sock_orphan(sk); + sock_set_flag(sk, SOCK_DEAD); if (vsk->transport) vsk->transport->release(vsk); else if (sock_type_connectible(sk->sk_type)) vsock_remove_sock(vsk); + sock_orphan(sk); sk->sk_shutdown = SHUTDOWN_MASK; skb_queue_purge(&sk->sk_receive_queue); I'm not sure this is the most elegant code (sock_orphan(sk) sets SOCK_DEAD on a socket that is already SOCK_DEAD), but here it goes: https://lore.kernel.org/netdev/20250204-vsock-linger-nullderef-v1-0-6eb1760fa93e@xxxxxxx/ One more note: man socket(7) says lingering also happens on shutdown(). Should vsock follow that? Thanks, Michal
