In the Linux kernel, the following vulnerability has been resolved:
nbd: Fix hung when signal interrupts nbd_start_device_ioctl()
syzbot reported hung task [1]. The following program is a simplified version of the reproducer:
int main(void) { int sv[2], fd;
if (socketpair(AF_UNIX, SOCK_STREAM, 0, sv) < 0)
return 1;
if ((fd = open(/dev/nbd0, 0)) < 0)
return 1;
if (ioctl(fd, NBD_SET_SIZE_BLOCKS, 0x81) < 0)
return 1;
if (ioctl(fd, NBD_SET_SOCK, sv[0]) < 0)
return 1;
if (ioctl(fd, NBD_DO_IT) < 0)
return 1;
return 0;
}
When signal interrupt nbd_start_device_ioctl() waiting the condition atomic_read(&config->recv_threads) == 0, the task can hung because it waits the completion of the inflight IOs.
This patch fixes the issue by clearing queue, not just shutdown, when signal interrupt nbd_start_device_ioctl().