Re: [PATCH] tipc: fix shutdown() of connectionless socket

So.

On Wed, Sep 02, 2020 at 08:09:54PM +0900, Tetsuo Handa wrote:

syzbot is reporting hung task at nbd_ioctl() [1], for there are two
problems regarding TIPC's connectionless socket's shutdown() operation.
I found C reproducer for this problem (shown below) from "no output from
test machine (2)" report.

----------

int main(int argc, char *argv[])
{
        const int fd = open("/dev/nbd0", 3);
        ioctl(fd, NBD_SET_SOCK, socket(PF_TIPC, SOCK_DGRAM, 0));

NBD expects a stream socket, not a datagram one.

        ioctl(fd, NBD_DO_IT, 0);

This is supposed to sit and wait until someone disconnects the device
again (which you probably cna't do with datagram sockets). Changing that
changes a userspace API.

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