From: Tetsuo Handa penguin-kernel@I-love.SAKURA.ne.jp
[ Upstream commit 2a63866c8b51a3f72cea388dfac259d0e14c4ba6 ]
syzbot is reporting hung task at nbd_ioctl() [1], for there are two problems regarding TIPC's connectionless socket's shutdown() operation.
---------- #include <fcntl.h> #include <sys/socket.h> #include <sys/ioctl.h> #include <linux/nbd.h> #include <unistd.h>
int main(int argc, char *argv[]) { const int fd = open("/dev/nbd0", 3); alarm(5); ioctl(fd, NBD_SET_SOCK, socket(PF_TIPC, SOCK_DGRAM, 0)); ioctl(fd, NBD_DO_IT, 0); /* To be interrupted by SIGALRM. */ return 0; } ----------
One problem is that wait_for_completion() from flush_workqueue() from nbd_start_device_ioctl() from nbd_ioctl() cannot be completed when nbd_start_device_ioctl() received a signal at wait_event_interruptible(), for tipc_shutdown() from kernel_sock_shutdown(SHUT_RDWR) from nbd_mark_nsock_dead() from sock_shutdown() from nbd_start_device_ioctl() is failing to wake up a WQ thread sleeping at wait_woken() from tipc_wait_for_rcvmsg() from sock_recvmsg() from sock_xmit() from nbd_read_stat() from recv_work() scheduled by nbd_start_device() from nbd_start_device_ioctl(). Fix this problem by always invoking sk->sk_state_change() (like inet_shutdown() does) when tipc_shutdown() is called.
The other problem is that tipc_wait_for_rcvmsg() cannot return when tipc_shutdown() is called, for tipc_shutdown() sets sk->sk_shutdown to SEND_SHUTDOWN (despite "how" is SHUT_RDWR) while tipc_wait_for_rcvmsg() needs sk->sk_shutdown set to RCV_SHUTDOWN or SHUTDOWN_MASK. Fix this problem by setting sk->sk_shutdown to SHUTDOWN_MASK (like inet_shutdown() does) when the socket is connectionless.
[1] https://syzkaller.appspot.com/bug?id=3fe51d307c1f0a845485cf1798aa059d12bf18b...
Reported-by: syzbot syzbot+e36f41d207137b5d12f7@syzkaller.appspotmail.com Signed-off-by: Tetsuo Handa penguin-kernel@I-love.SAKURA.ne.jp Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/tipc/socket.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-)
--- a/net/tipc/socket.c +++ b/net/tipc/socket.c @@ -2126,18 +2126,21 @@ static int tipc_shutdown(struct socket * lock_sock(sk);
__tipc_shutdown(sock, TIPC_CONN_SHUTDOWN); - sk->sk_shutdown = SEND_SHUTDOWN; + if (tipc_sk_type_connectionless(sk)) + sk->sk_shutdown = SHUTDOWN_MASK; + else + sk->sk_shutdown = SEND_SHUTDOWN;
if (sk->sk_state == TIPC_DISCONNECTING) { /* Discard any unreceived messages */ __skb_queue_purge(&sk->sk_receive_queue);
- /* Wake up anyone sleeping in poll */ - sk->sk_state_change(sk); res = 0; } else { res = -ENOTCONN; } + /* Wake up anyone sleeping in poll. */ + sk->sk_state_change(sk);
release_sock(sk); return res;