From: Matthew Wilcox <willy@infradead.org>
To: Uladzislau Rezki <urezki@gmail.com>
Cc: Zorro Lang <zlang@redhat.com>,
Alexander Gordeev <agordeev@linux.ibm.com>,
bugzilla-daemon@kernel.org, linux-s390@vger.kernel.org,
linux-xfs@vger.kernel.org,
Andrew Morton <akpm@linux-foundation.org>,
linux-mm@kvack.org, Kees Cook <keescook@chromium.org>
Subject: Re: [Bug 216073] New: [s390x] kernel BUG at mm/usercopy.c:101! usercopy: Kernel memory exposure attempt detected from vmalloc 'n o area' (offset 0, size 1)!
Date: Sun, 12 Jun 2022 18:26:43 +0100 [thread overview]
Message-ID: <YqYh0xyJvoNsSOpy@casper.infradead.org> (raw)
In-Reply-To: <YqXkGMY9xtUvPR5D@pc638.lan>
On Sun, Jun 12, 2022 at 03:03:20PM +0200, Uladzislau Rezki wrote:
> > @@ -181,8 +181,9 @@ static inline void check_heap_object(const void *ptr, unsigned long n,
> > return;
> > }
> >
> > - offset = ptr - area->addr;
> > - if (offset + n > get_vm_area_size(area))
> > + /* XXX: We should also abort for free vmap_areas */
> > + offset = (unsigned long)ptr - area->va_start;
> >
> I was a bit confused about "offset" and why it is needed here. It is always zero.
> So we can get rid of it to make it less confused. From the other hand a zero offset
> contributes to nothing.
I don't think offset is necessarily zero. 'ptr' is a pointer somewhere
in the object, not necessarily the start of the object.
> >
> > + if (offset + n >= area->va_end)
> >
> I think it is a bit wrong. As i see it, "n" is a size and what we would like to do
> here is boundary check:
>
> <snip>
> if (n > va_size(area))
> usercopy_abort("vmalloc", NULL, to_user, 0, n);
> <snip>
Hmm ... we should probably be more careful about wrapping.
if (n > area->va_end - addr)
usercopy_abort("vmalloc", NULL, to_user, offset, n);
... and that goes for the whole function actually. I'll split that into
a separate change.
next prev parent reply other threads:[~2022-06-12 17:26 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <bug-216073-27@https.bugzilla.kernel.org/>
2022-06-06 22:13 ` [Bug 216073] New: [s390x] kernel BUG at mm/usercopy.c:101! usercopy: Kernel memory exposure attempt detected from vmalloc 'n o area' (offset 0, size 1)! Andrew Morton
2022-06-07 15:05 ` Alexander Gordeev
2022-06-08 2:19 ` Zorro Lang
2022-06-08 19:13 ` Alexander Gordeev
2022-06-09 2:49 ` Zorro Lang
2022-06-12 4:42 ` Zorro Lang
2022-06-12 11:58 ` Matthew Wilcox
2022-06-12 13:03 ` Uladzislau Rezki
2022-06-12 17:26 ` Matthew Wilcox [this message]
2022-06-12 17:59 ` Yu Zhao
2022-06-12 18:05 ` Matthew Wilcox
2022-06-12 18:43 ` Yu Zhao
2022-06-12 19:52 ` Matthew Wilcox
2022-06-12 20:53 ` Yu Zhao
2022-06-12 19:07 ` Uladzislau Rezki
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