io_uring: don't guard IORING_OFF_PBUF_RING with SETUP_NO_MMAP

This flag only applies to the SQ and CQ rings, it's perfectly valid
to use a mmap approach for the provided ring buffers. Move the
check into where it belongs.

Cc: stable@vger.kernel.org
Fixes: 03d89a2d ("io_uring: support for user allocated memory for rings/sqes")
Signed-off-by: Jens Axboe <axboe@kernel.dk>

io_uring/io_uring.c

@@ -3478,16 +3478,18 @@ static void *io_uring_validate_mmap_request(struct file *file,
 	struct page *page;
 	void *ptr;
 
-	/* Don't allow mmap if the ring was setup without it */
-	if (ctx->flags & IORING_SETUP_NO_MMAP)
-		return ERR_PTR(-EINVAL);
-
 	switch (offset & IORING_OFF_MMAP_MASK) {
 	case IORING_OFF_SQ_RING:
 	case IORING_OFF_CQ_RING:
+		/* Don't allow mmap if the ring was setup without it */
+		if (ctx->flags & IORING_SETUP_NO_MMAP)
+			return ERR_PTR(-EINVAL);
 		ptr = ctx->rings;
 		break;
 	case IORING_OFF_SQES:
+		/* Don't allow mmap if the ring was setup without it */
+		if (ctx->flags & IORING_SETUP_NO_MMAP)
+			return ERR_PTR(-EINVAL);
 		ptr = ctx->sq_sqes;
 		break;
 	case IORING_OFF_PBUF_RING: {