ppc32 selinux mprotect diff.

[Stephen Smalley]

On Mon, 2010-01-11 at 14:55 -0500, Dave Jones wrote:
> We've carried this diff in Fedora for a few years now..
> 
> --- linux-2.6.26.noarch/security/selinux/hooks.c~	2008-09-25 14:11:17.000000000 -0400
> +++ linux-2.6.26.noarch/security/selinux/hooks.c	2008-09-25 14:12:17.000000000 -0400
> @@ -3018,7 +3018,6 @@ static int file_map_prot_check(struct fi
>  	const struct cred *cred = current_cred();
>  	int rc = 0;
>  
> -#ifndef CONFIG_PPC32
>  	if ((prot & PROT_EXEC) && (!file || (!shared && (prot & PROT_WRITE)))) {
>  		/*
>  		 * We are making executable an anonymous mapping or a
> @@ -3029,7 +3028,6 @@ static int file_map_prot_check(struct fi
>  		if (rc)
>  			goto error;
>  	}
> -#endif
>  
>  	if (file) {
>  		/* read access is always possible with a mapping */
> @@ -3024,7 +3022,6 @@ static int selinux_file_mprotect(struct 
>  	if (selinux_checkreqprot)
>  		prot = reqprot;
>  
> -#ifndef CONFIG_PPC32
>  	if ((prot & PROT_EXEC) && !(vma->vm_flags & VM_EXEC)) {
>  		rc = 0;
>  		if (vma->vm_start >= vma->vm_mm->start_brk &&
> @@ -3049,7 +3046,6 @@ static int selinux_file_mprotect(struct 
>  		if (rc)
>  			return rc;
>  	}
> -#endif
>  
>  	return file_map_prot_check(vma->vm_file, prot, vma->vm_flags&VM_SHARED);
>  }
> 
> 
> 
> This needs a fixed toolchain, and a userspace rebuild to work.
> For these reasons, it's had difficulty getting upstream.
> 
> Fedora has a new enough toolchain, and has been rebuilt, so we don't need
> the ifdefs.  Other distros don't/haven't, and this patch would break them
> if pushed upstream.
> 
> Could we do something like the (untested) diff below instead,
> which might be more palatable to upstream, allowing us to stop
> carrying it ?
> 
> 	Dave
> 
> diff --git a/security/selinux/Kconfig b/security/selinux/Kconfig
> index bca1b74..83a9675 100644
> --- a/security/selinux/Kconfig
> +++ b/security/selinux/Kconfig
> @@ -131,3 +131,10 @@ config SECURITY_SELINUX_POLICYDB_VERSION_MAX_VALUE
>  	  installed under /etc/selinux/$SELINUXTYPE/policy, where
>  	  SELINUXTYPE is defined in your /etc/selinux/config.
>  
> +config SELINUX_NEW_ENOUGH_TOOLCHAIN
> +	bool "SELinux mprotect checks"
> +	default n if PPC32
> +	help
> +	  This option requires a modern toolchain (FIXME: Version?)
> +	  and a userspace rebuild to work.
> +
> diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
> index 9a2ee84..e805df7 100644
> --- a/security/selinux/hooks.c
> +++ b/security/selinux/hooks.c
> @@ -3009,7 +3009,7 @@ static int file_map_prot_check(struct file *file, unsigned long prot, int shared
>  	const struct cred *cred = current_cred();
>  	int rc = 0;
>  
> -#ifndef CONFIG_PPC32
> +#ifdef CONFIG_SELINUX_NEW_ENOUGH_TOOLCHAIN
>  	if ((prot & PROT_EXEC) && (!file || (!shared && (prot & PROT_WRITE)))) {
>  		/*
>  		 * We are making executable an anonymous mapping or a
> @@ -3081,7 +3081,7 @@ static int selinux_file_mprotect(struct vm_area_struct *vma,
>  	if (selinux_checkreqprot)
>  		prot = reqprot;
>  
> -#ifndef CONFIG_PPC32
> +#ifdef CONFIG_SELINUX_NEW_ENOUGH_TOOLCHAIN
>  	if ((prot & PROT_EXEC) && !(vma->vm_flags & VM_EXEC)) {
>  		int rc = 0;
>  		if (vma->vm_start >= vma->vm_mm->start_brk &&

IMHO, we should just do one of the following:
1) Push the original diff (i.e. drop the #ifndef CONFIG_PPC32) upstream
and see if anyone complains.
-or-
2) Drop the diff altogether and forget about exec* checking on ppc32.

I wouldn't favor the new option.

-- 
Stephen Smalley
National Security Agency