On 2020/09/03 20:31, Wouter Verhelst wrote:
> 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.
>
Excuse me, but other datagram sockets (e.g. socket(PF_INET, SOCK_DGRAM, 0))
does not
hit this problem. What do you want to do? Add a "whether the file descriptor
passed
to ioctl(NBD_SET_SOCK) is a SOCK_STREAM socket" test to the NBD side?
I think that regardless of whether NBD expects only SOCK_STREAM sockets,
tipc_wait_for_rcvmsg() on a SOCK_DGRAM socket can't return is a bug.
David Miller already applied this patch and queued up for -stable.
Do we need to revert this patch?
