linux-hardening - Re: [RFC PATCH v5 2/4] mseal: add mseal syscall

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Date: Wed, 10 Jan 2024 18:58:48 -0800
From: Jeff Xu <jeffxu@...omium.org>
To: Matthew Wilcox <willy@...radead.org>
Cc: akpm@...ux-foundation.org, keescook@...omium.org, jannh@...gle.com, 
	sroettger@...gle.com, gregkh@...uxfoundation.org, 
	torvalds@...ux-foundation.org, usama.anjum@...labora.com, jeffxu@...gle.com, 
	jorgelo@...omium.org, groeck@...omium.org, linux-kernel@...r.kernel.org, 
	linux-kselftest@...r.kernel.org, linux-mm@...ck.org, pedro.falcato@...il.com, 
	dave.hansen@...el.com, linux-hardening@...r.kernel.org, deraadt@...nbsd.org
Subject: Re: [RFC PATCH v5 2/4] mseal: add mseal syscall

On Tue, Jan 9, 2024 at 12:36 PM Matthew Wilcox <willy@...radead.org> wrote:
>
> On Tue, Jan 09, 2024 at 03:45:40PM +0000, jeffxu@...omium.org wrote:
> > +extern bool can_modify_mm(struct mm_struct *mm, unsigned long start,
> > +             unsigned long end);
> > +extern bool can_modify_mm_madv(struct mm_struct *mm, unsigned long start,
> > +             unsigned long end, int behavior);
>
> unnecessary use of extern.
>
> > +static inline unsigned long get_mmap_seals(unsigned long prot,
> > +     unsigned long flags)
>
> needs more than one tab indent so it doesn't look like part of the body.
>
> > +{
> > +     unsigned long vm_seals;
> > +
> > +     if (prot & PROT_SEAL)
> > +             vm_seals = VM_SEALED | VM_SEALABLE;
> > +     else
> > +             vm_seals = (flags & MAP_SEALABLE) ? VM_SEALABLE:0;
>
> need spaces around the :
>
> > +++ b/include/uapi/asm-generic/mman-common.h
> > @@ -17,6 +17,11 @@
> >  #define PROT_GROWSDOWN       0x01000000      /* mprotect flag: extend change to start of growsdown vma */
> >  #define PROT_GROWSUP 0x02000000      /* mprotect flag: extend change to end of growsup vma */
> >
> > +/*
> > + * The PROT_SEAL defines memory sealing in the prot argument of mmap().
> > + */
> > +#define PROT_SEAL    _BITUL(26)      /* 0x04000000 */
>
> why not follow the existing style?
>
> > +static inline void set_vma_sealed(struct vm_area_struct *vma)
> > +{
> > +     vma->__vm_flags |= VM_SEALED;
> > +}
>
> uhh ... vm_flags_set() ?
>
Thanks. I agree with all the comments above and will update in the next version.

-Jeff