linux-hardening - Re: [PATCH v1 1/2] mseal: fix mmap(FIXED) error code.

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Message-ID: <CABi2SkWkdHErmp3Fjx+_aZXr=V3gBKfE8Nk9ESfB32N+FMCpog@mail.gmail.com>
Date: Thu, 29 Aug 2024 07:34:33 -0700
From: Jeff Xu <jeffxu@...omium.org>
To: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
Cc: akpm@...ux-foundation.org, linux-kselftest@...r.kernel.org, 
	linux-mm@...ck.org, linux-hardening@...r.kernel.org, pedro.falcato@...il.com, 
	rientjes@...gle.com, keescook@...omium.org, 
	Liam Howlett <liam.howlett@...cle.com>, vbabka@...e.cz
Subject: Re: [PATCH v1 1/2] mseal: fix mmap(FIXED) error code.

On Thu, Aug 29, 2024 at 5:09 AM Lorenzo Stoakes
<lorenzo.stoakes@...cle.com> wrote:
>
> Jeff... come on now.
>
> Please cc- the reviewers of mm/mmap.c on these patches - that's me,
> Vlastimil and Liam. Same for mm/vma.c, mm/vma.h, mm/vma_internal.h.
>
sure, that was a small fix and I thought introduced by Pedro's commit
(which was wrong)

> And it seems like it should be pretty obvious you should cc- Liam when it's
> quite literally his code you're changing!
>
> Relevant section from MAINTAINERS:
>
> MEMORY MAPPING
> M:      Andrew Morton <akpm@...ux-foundation.org>
> R:      Liam R. Howlett <Liam.Howlett@...cle.com>
> R:      Vlastimil Babka <vbabka@...e.cz>
> R:      Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
> L:      linux-mm@...ck.org
> S:      Maintained
> W:      http://www.linux-mm.org
> T:      git git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
> F:      mm/mmap.c
>
> On Wed, Aug 28, 2024 at 10:55:21PM GMT, jeffxu@...omium.org wrote:
> > From: Jeff Xu <jeffxu@...omium.org>
> >
> > mmap(MAP_FIXED) should return EPERM when memory is sealed.
> >
> > Fixes: 4205a39e06da ("mm/munmap: replace can_modify_mm with can_modify_vma")
> > Signed-off-by: Jeff Xu <jeffxu@...omium.org>
> > ---
> >  mm/mmap.c | 5 ++++-
> >  1 file changed, 4 insertions(+), 1 deletion(-)
> >
> > diff --git a/mm/mmap.c b/mm/mmap.c
> > index 80d70ed099cf..0cd0c0ef03c7 100644
> > --- a/mm/mmap.c
> > +++ b/mm/mmap.c
> > @@ -1386,7 +1386,10 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
> >               mt_on_stack(mt_detach);
> >               mas_init(&mas_detach, &mt_detach, /* addr = */ 0);
> >               /* Prepare to unmap any existing mapping in the area */
> > -             if (vms_gather_munmap_vmas(&vms, &mas_detach))
> > +             error = vms_gather_munmap_vmas(&vms, &mas_detach);
> > +             if (error == -EPERM)
> > +                     return -EPERM;
> > +             if (error)
> >                       return -ENOMEM;
>
> Can't we just return the error here?
>
> This is one for Liam, but I'm ostensibly in favour, this does seem valid!
>
> >
> >               vmg.next = vms.next;
> > --
> > 2.46.0.295.g3b9ea8a38a-goog
> >