io_uring/memmap: explicitly return -EFAULT for mmap on NULL rings

The later mapping will actually check this too, but in terms of code
clarify, explicitly check for whether or not the rings and sqes are
valid during validation. That makes it explicit that if they are
non-NULL, they are valid and can get mapped.

Signed-off-by: Jens Axboe <[email protected]>

Author: axboe

io_uring/memmap.c

@@ -204,11 +204,15 @@ static void *io_uring_validate_mmap_request(struct file *file, loff_t pgoff,
 		/* Don't allow mmap if the ring was setup without it */
 		if (ctx->flags & IORING_SETUP_NO_MMAP)
 			return ERR_PTR(-EINVAL);
+		if (!ctx->rings)
+			return ERR_PTR(-EFAULT);
 		return ctx->rings;
 	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);
+		if (!ctx->sq_sqes)
+			return ERR_PTR(-EFAULT);
 		return ctx->sq_sqes;
 	case IORING_OFF_PBUF_RING: {
 		struct io_buffer_list *bl;