Re: [PATCHv4 2/5] io_uring: add support for kernel registered bvecs

Pavel Begunkov <asml.silence@xxxxxxxxx> · Thu, 20 Feb 2025 10:31:55 +0000




On 2/19/25 01:54, Caleb Sander Mateos wrote:
On Tue, Feb 18, 2025 at 2:42 PM Keith Busch <kbusch@xxxxxxxx> wrote:
...
  int io_import_fixed(int ddir, struct iov_iter *iter,
                            struct io_mapped_ubuf *imu,
                            u64 buf_addr, size_t len)
@@ -874,6 +963,9 @@ int io_import_fixed(int ddir, struct iov_iter *iter,
         /* not inside the mapped region */
         if (unlikely(buf_addr < imu->ubuf || buf_end > (imu->ubuf + imu->len)))
                 return -EFAULT;
+       if ((ddir == READ && !imu->readable) ||
+           (ddir == WRITE && !imu->writeable))
+               return -EFAULT;

This could be made less branchy by storing a bitmask of allowed data
transfer directions instead of 2 bool fields. Then this could just be:
if (!(imu->ddirs >> ddir & 1)
         return -EFAULT;

I'd prefer a direction mask indeed.

--
Pavel Begunkov








