linux-kernel - Re: [RFC PATCH v4 01/13] ptrace: Use regset

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Date:   Tue, 26 May 2020 16:00:28 +0200
From:   Oleg Nesterov <oleg@...hat.com>
To:     Greentime Hu <greentime.hu@...ive.com>
Cc:     guoren@...ux.alibaba.com, vincent.chen@...ive.com,
        paul.walmsley@...ive.com, palmerdabbelt@...gle.com,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH v4 01/13] ptrace: Use regset_size() for dynamic
 regset size.

On 05/26, Greentime Hu wrote:
>
> @@ -882,13 +882,18 @@ static int ptrace_regset(struct task_struct *task, int req, unsigned int type,
>  	const struct user_regset_view *view = task_user_regset_view(task);
>  	const struct user_regset *regset = find_regset(view, type);
>  	int regset_no;
> +	unsigned int size;
>
> -	if (!regset || (kiov->iov_len % regset->size) != 0)
> +	if (!regset)
>  		return -EINVAL;
>
>  	regset_no = regset - view->regsets;
> -	kiov->iov_len = min(kiov->iov_len,
> -			    (__kernel_size_t) (regset->n * regset->size));
> +	size = regset_size(task, regset);
> +
> +	if ((kiov->iov_len % size) != 0)
> +		return -EINVAL;

Hmm. this doesn't look right.

Before this patch we check "iov_len % regset->size", this is not the same
as "iov_len % regset_size()".

IOW, currently you can read/write, say, only the 1st register, you patch
breaks this?

Oleg.