io_uring/rsrc: improve regbuf iov validation

Deduplicate io_buffer_validate() calls by moving the checks into
io_sqe_buffer_register(). Now we also don't need special handling in
io_buffer_validate() passing through buffer removal requests. I also
was using it as a cleanup before some other changes.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Author: isilence

io_uring/rsrc.c

@@ -96,20 +96,6 @@ int io_validate_user_buf_range(u64 uaddr, u64 ulen)
 	return 0;
 }
 
-static int io_buffer_validate(struct iovec *iov)
-{
-	/*
-	 * Don't impose further limits on the size and buffer
-	 * constraints here, we'll -EINVAL later when IO is
-	 * submitted if they are wrong.
-	 */
-	if (!iov->iov_base)
-		return iov->iov_len ? -EFAULT : 0;
-
-	return io_validate_user_buf_range((unsigned long)iov->iov_base,
-					  iov->iov_len);
-}
-
 static void io_release_ubuf(void *priv)
 {
 	struct io_mapped_ubuf *imu = priv;
@@ -319,9 +305,6 @@ static int __io_sqe_buffers_update(struct io_ring_ctx *ctx,
 			err = -EFAULT;
 			break;
 		}
-		err = io_buffer_validate(iov);
-		if (err)
-			break;
 		node = io_sqe_buffer_register(ctx, iov, &last_hpage);
 		if (IS_ERR(node)) {
 			err = PTR_ERR(node);
@@ -790,8 +773,17 @@ static struct io_rsrc_node *io_sqe_buffer_register(struct io_ring_ctx *ctx,
 	struct io_imu_folio_data data;
 	bool coalesced = false;
 
-	if (!iov->iov_base)
+	if (!iov->iov_base) {
+		if (iov->iov_len)
+			return ERR_PTR(-EFAULT);
+		/* remove the buffer without installing a new one */
 		return NULL;
+	}
+
+	ret = io_validate_user_buf_range((unsigned long)iov->iov_base,
+					 iov->iov_len);
+	if (ret)
+		return ERR_PTR(ret);
 
 	node = io_rsrc_node_alloc(ctx, IORING_RSRC_BUFFER);
 	if (!node)
@@ -897,9 +889,6 @@ int io_sqe_buffers_register(struct io_ring_ctx *ctx, void __user *arg,
 				ret = PTR_ERR(iov);
 				break;
 			}
-			ret = io_buffer_validate(iov);
-			if (ret)
-				break;
 			if (ctx->compat)
 				arg += sizeof(struct compat_iovec);
 			else