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Date: Fri, 30 Jan 2026 06:11:25 +0100
From: Christoph Hellwig <hch@lst.de>
To: Govindarajulu Varadarajan <govind.varadar@gmail.com>
Cc: io-uring@vger.kernel.org, axboe@kernel.dk, ming.lei@redhat.com,
	kbusch@kernel.org, hch@lst.de, sagi@grimberg.me, miklos@szeredi.hu
Subject: Re: [PATCH 1/2] io_uring: Add size check for sqe->cmd
Message-ID: <20260130051125.GB32492@lst.de>
References: <20260129201347.411015-1-govind.varadar@gmail.com> <20260129201347.411015-2-govind.varadar@gmail.com>
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On Thu, Jan 29, 2026 at 12:13:46PM -0800, Govindarajulu Varadarajan wrote:
> -	const struct ublksrv_io_cmd *ub_src = io_uring_sqe_cmd(cmd->sqe);
> +	const struct ublksrv_io_cmd *ub_src = IO_URING_SQE_CMD(cmd->sqe, struct ublksrv_io_cmd);

As Jens already said, no need for the shouting.  Also please break the
lines to keep things readable.

> -static inline const void *io_uring_sqe_cmd(const struct io_uring_sqe *sqe)
> -{
> -	return sqe->cmd;
> -}
> +#define IO_URING_SQE128_CMD(sqe, type)	({						\
> +	BUILD_BUG_ON(sizeof(type) > ((2 * sizeof(struct io_uring_sqe)) -		\
> +				     offsetof(struct io_uring_sqe, cmd)));		\
> +	(type *)(sqe)->cmd;								\
> +})
> +
> +#define IO_URING_SQE_CMD(sqe, type)	({						\
> +	BUILD_BUG_ON(sizeof(type) > ((sizeof(struct io_uring_sqe)) -			\
> +				     offsetof(struct io_uring_sqe, cmd)));		\
> +	(type *)(sqe)->cmd;								\
> +})

I'm also not sure adding a BUILD_BUG_ON to every derefence is great for
compile times.  But I'm not really sure what would be a good other
place for it.