Re: [RFC] c/r: prctl: Add ability to set new mm_struct::exe_file v3

[Kees Cook]

On Thu, Mar 8, 2012 at 1:57 PM, Cyrill Gorcunov <gorcunov@xxxxxxxxxx> wrote:
> On Thu, Mar 08, 2012 at 12:24:38PM -0800, Andy Lutomirski wrote:
>>
>> nnp is no_new_privs, which is my patch and is almost, but not quite,
>> very relevant to this discussion.  Hence my confusion ;)
>>
>> FWIW, since I've touched this code recently, the cleanup you're
>> suggesting sounds good.
>>
>
> Andy, Kees, I guess the patch below might be a helper we need,
> while I'm not sure on naming. hm?
>
>        Cyrill
> ---
>  include/linux/fs.h |    6 ++++++
>  1 file changed, 6 insertions(+)
>
> Index: linux-2.6.git/include/linux/fs.h
> ===================================================================
> --- linux-2.6.git.orig/include/linux/fs.h
> +++ linux-2.6.git/include/linux/fs.h
> @@ -2669,5 +2669,11 @@ static inline void inode_has_no_xattr(st
>                inode->i_flags |= S_NOSEC;
>  }
>
> +static inline bool file_may_exec(struct file *f)
> +{
> +       return S_ISREG(f->f_path.dentry->d_inode->i_mode) &&
> +               !(f->f_path.mnt->mnt_flags & MNT_NOEXEC);
> +}
> +
>  #endif /* __KERNEL__ */
>  #endif /* _LINUX_FS_H */

How about "file_is_exec" instead, since it doesn't (and likely
shouldn't) include the inode_permission(..., EXEC)? I'd like other
people's thoughts on this since maybe it's not needed and I instead
have accidentally derailed this patch with useless bike shedding.

-Kees

-- 
Kees Cook
ChromeOS Security
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