From: Kees Cook <keescook@chromium.org>
To: Matthew Wilcox <willy@infradead.org>
Cc: linux-mm@kvack.org, Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH 1/3] mm/usercopy: Check kmap addresses properly
Date: Tue, 5 Oct 2021 14:54:13 -0700 [thread overview]
Message-ID: <202110051453.A2002FE@keescook> (raw)
In-Reply-To: <YVzG8crVL0XrstXg@casper.infradead.org>
On Tue, Oct 05, 2021 at 10:43:13PM +0100, Matthew Wilcox wrote:
> On Tue, Oct 05, 2021 at 02:23:09PM -0700, Kees Cook wrote:
> > > + if (is_kmap_addr(ptr)) {
> > > + unsigned long page_end = (unsigned long)ptr | (PAGE_SIZE - 1);
> > > +
> > > + if ((unsigned long)ptr + n - 1 > page_end)
> > > + usercopy_abort("kmap", NULL, to_user, 0, n);
> >
> > It's likely not worth getting an offset here, but "0" above could be
> > something like "ptr - PKMAP_ADDR(0)".
>
> Mmm. page_offset(ptr) should do the trick, no?
Ah yeah, that'd be good!
-Kees
>
> > Either way:
> >
> > Acked-by: Kees Cook <keescook@chromium.org>
> >
> > Thanks!
> >
> > -Kees
> >
> > > + return;
> > > + }
> > > +
> > > + page = virt_to_head_page(ptr);
> > >
> > > if (PageSlab(page)) {
> > > /* Check slab allocator for flags and size. */
> > > --
> > > 2.32.0
> > >
> >
> > --
> > Kees Cook
--
Kees Cook
next prev parent reply other threads:[~2021-10-05 21:54 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-04 22:42 [PATCH 0/3] Assorted improvements to usercopy Matthew Wilcox (Oracle)
2021-10-04 22:42 ` [PATCH 1/3] mm/usercopy: Check kmap addresses properly Matthew Wilcox (Oracle)
2021-10-05 21:23 ` Kees Cook
2021-10-05 21:43 ` Matthew Wilcox
2021-10-05 21:54 ` Kees Cook [this message]
2021-10-04 22:42 ` [PATCH 2/3] mm/usercopy: Detect vmalloc overruns Matthew Wilcox (Oracle)
2021-10-05 21:25 ` Kees Cook
2021-10-06 1:26 ` Matthew Wilcox
2021-10-06 3:02 ` Kees Cook
2021-10-04 22:42 ` [PATCH 3/3] mm/usercopy: Detect compound page overruns Matthew Wilcox (Oracle)
2021-10-05 21:26 ` Kees Cook
2021-10-05 22:12 ` Matthew Wilcox
2021-10-05 22:55 ` Kees Cook
2021-10-05 21:27 ` [PATCH 0/3] Assorted improvements to usercopy Kees Cook
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