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Date:   Wed, 13 May 2020 20:05:09 -0700
From:   Kees Cook <keescook@chromium.org>
To:     Stephen Smalley <stephen.smalley.work@gmail.com>
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Subject: Re: [PATCH v5 3/6] fs: Enable to enforce noexec mounts or file exec
 through O_MAYEXEC
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On Wed, May 13, 2020 at 04:27:39PM -0700, Kees Cook wrote:
> Like, couldn't just the entire thing just be:
> 
> diff --git a/fs/namei.c b/fs/namei.c
> index a320371899cf..0ab18e19f5da 100644
> --- a/fs/namei.c
> +++ b/fs/namei.c
> @@ -2849,6 +2849,13 @@ static int may_open(const struct path *path, int acc_mode, int flag)
>  		break;
>  	}
>  
> +	if (unlikely(mask & MAY_OPENEXEC)) {
> +		if (sysctl_omayexec_enforce & OMAYEXEC_ENFORCE_MOUNT &&
> +		    path_noexec(path))
> +			return -EACCES;
> +		if (sysctl_omayexec_enforce & OMAYEXEC_ENFORCE_FILE)
> +			acc_mode |= MAY_EXEC;
> +	}
>  	error = inode_permission(inode, MAY_OPEN | acc_mode);
>  	if (error)
>  		return error;
> 

FYI, I've confirmed this now. Effectively with patch 2 dropped, patch 3
reduced to this plus the Kconfig and sysctl changes, the self tests
pass.

I think this makes things much cleaner and correct.

-- 
Kees Cook