On 1/29/19 8:35 AM, Jann Horn wrote:
> On Mon, Jan 28, 2019 at 10:35 PM Jens Axboe <axboe@xxxxxxxxx> wrote:
>> The submission queue (SQ) and completion queue (CQ) rings are shared
>> between the application and the kernel. This eliminates the need to
>> copy data back and forth to submit and complete IO.
> [...]
>> +static int io_import_iovec(struct io_ring_ctx *ctx, int rw,
>> + const struct io_uring_sqe *sqe,
>> + struct iovec **iovec, struct iov_iter *iter)
>> +{
>> + void __user *buf = u64_to_user_ptr(sqe->addr);
>> +
>> +#ifdef CONFIG_COMPAT
>> + if (in_compat_syscall())
>> + return compat_import_iovec(rw, buf, sqe->len, UIO_FASTIOV,
>> + iovec, iter);
>> +#endif
>> +
>> + return import_iovec(rw, buf, sqe->len, UIO_FASTIOV, iovec, iter);
>> +}
>
> This code can run in kthread context, right? I think
> in_compat_syscall() might not work if this is a kthread launched by a
> compat task; I don't see anything that propagates the compat flag to
> the kthread.
Good catch, yes it can. We should just carry this information in
sqe_submit for this out-of-line purpose. I'll make that change.
--
Jens Axboe
