[RFC 2/7] io_uring: add reg-buffer data directions

[Pavel Begunkov <asml.silence@xxxxxxxxx>]

There will be buffers that only allow reading from or writing to it, so
add data directions, and check it when importing a buffer.

Signed-off-by: Pavel Begunkov <asml.silence@xxxxxxxxx>
---
 io_uring/rsrc.c | 5 +++++
 io_uring/rsrc.h | 1 +
 2 files changed, 6 insertions(+)

diff --git a/io_uring/rsrc.c b/io_uring/rsrc.c
index fef94f8d788d..b6305ae3538c 100644
--- a/io_uring/rsrc.c
+++ b/io_uring/rsrc.c
@@ -1185,6 +1185,7 @@ static int io_sqe_buffer_register(struct io_ring_ctx *ctx, struct iovec *iov,
 	imu->ubuf = (unsigned long) iov->iov_base;
 	imu->ubuf_end = imu->ubuf + iov->iov_len;
 	imu->nr_bvecs = nr_pages;
+	imu->dir_mask = (1U << ITER_SOURCE) | (1U << ITER_DEST);
 	*pimu = imu;
 	ret = 0;
 
@@ -1274,6 +1275,8 @@ int io_import_fixed(int ddir, struct iov_iter *iter,
 	u64 buf_end;
 	size_t offset;
 
+	BUILD_BUG_ON((1U << ITER_SOURCE) & (1U << ITER_DEST));
+
 	if (WARN_ON_ONCE(!imu))
 		return -EFAULT;
 	if (unlikely(check_add_overflow(buf_addr, (u64)len, &buf_end)))
@@ -1281,6 +1284,8 @@ 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_end))
 		return -EFAULT;
+	if (unlikely(!((1U << ddir) & imu->dir_mask)))
+		return -EFAULT;
 
 	/*
 	 * Might not be a start of buffer, set size appropriately
diff --git a/io_uring/rsrc.h b/io_uring/rsrc.h
index f34de451a79a..10daa25d9194 100644
--- a/io_uring/rsrc.h
+++ b/io_uring/rsrc.h
@@ -57,6 +57,7 @@ struct io_mapped_ubuf {
 	u64		ubuf_end;
 	unsigned int	nr_bvecs;
 	unsigned int	max_bvecs;
+	unsigned int	dir_mask;
 	unsigned long	acct_pages;
 	struct bio_vec	bvec[];
 };
-- 
2.40.0