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

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Message-ID: <CABi2SkXxkzypPiXpjk+fuXBpdgkpCWD=z-Rzk=zFbSkY7xON1g@mail.gmail.com>
Date: Thu, 29 Aug 2024 07:32:58 -0700
From: Jeff Xu <jeffxu@...omium.org>
To: Pedro Falcato <pedro.falcato@...il.com>
Cc: akpm@...ux-foundation.org, linux-kselftest@...r.kernel.org, 
	linux-mm@...ck.org, linux-hardening@...r.kernel.org, rientjes@...gle.com, 
	keescook@...omium.org, Liam.Howlett@...cle.com, vbabka@...e.cz, 
	lorenzo.stoakes@...cle.com
Subject: Re: [PATCH v1 1/2] mseal: fix mmap(FIXED) error code.

On Wed, Aug 28, 2024 at 4:38 PM Pedro Falcato <pedro.falcato@...il.com> wrote:
>
> +CC vma reviewers
> 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")
>
> Thank you for the patch!
> This Fixes: is wrong, the bug was added during Liam's rebasing of his munmap patch
> set on mine.
>
ok.

> > 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;
>
> Not sure if it makes sense to special case this. We should probably deal with this inside
> vms_gather_munmap_vmas and just pass through the error we get.
>
> Otherwise LGTM. Liam?
>
> (we should also squash this into the offending commit)
>
> --
> Pedro