linux-kernel - Re: [PATCH 10/18] maccess: unify the probe kernel arch hooks

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Date:   Thu, 14 May 2020 10:13:18 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Christoph Hellwig <hch@....de>
Cc:     x86@...nel.org, Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-parisc@...r.kernel.org, linux-um@...ts.infradead.org,
        netdev@...r.kernel.org, bpf@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 10/18] maccess: unify the probe kernel arch hooks

Hi Christoph,

On Wed, 13 May 2020 18:00:30 +0200
Christoph Hellwig <hch@....de> wrote:

> @@ -36,14 +50,20 @@ long __weak probe_kernel_read(void *dst, const void *src, size_t size)
>   * probe_kernel_read() suitable for use within regions where the caller
>   * already holds mmap_sem, or other locks which nest inside mmap_sem.
>   */
> -long __weak probe_kernel_read_strict(void *dst, const void *src, size_t size)
> -    __attribute__((alias("__probe_kernel_read")));
> +long probe_kernel_read_strict(void *dst, const void *src, size_t size)
> +{
> +	return __probe_kernel_read(dst, src, size, true);
> +}
>  
> -long __probe_kernel_read(void *dst, const void *src, size_t size)
> +static long __probe_kernel_read(void *dst, const void *src, size_t size,
> +		bool strict)
>  {
>  	long ret;
>  	mm_segment_t old_fs = get_fs();
>  
> +	if (!probe_kernel_read_allowed(dst, src, size, strict))
> +		return -EFAULT;

Could you make this return -ERANGE instead of -EFAULT so that
the caller can notice that the address might be user space?

Thank you,

-- 
Masami Hiramatsu <mhiramat@...nel.org>