From: Christophe Leroy <christophe.leroy@csgroup.eu>
To: Michael Ellerman <mpe@ellerman.id.au>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Paul Mackerras <paulus@samba.org>
Cc: linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH] powerpc/mm: Don't see NULL pointer dereference as a KUAP fault
Date: Fri, 4 Dec 2020 07:30:52 +0100 [thread overview]
Message-ID: <16dd1637-cfaf-bfb3-07c6-7e71d33640b8@csgroup.eu> (raw)
In-Reply-To: <87mtyvumrn.fsf@mpe.ellerman.id.au>
Le 03/12/2020 à 12:55, Michael Ellerman a écrit :
> Christophe Leroy <christophe.leroy@csgroup.eu> writes:
>> Sometimes, NULL pointer dereferences are expected. Even when they
>> are accidental they are unlikely an exploit attempt because the
>> first page is never mapped.
>
> The first page can be mapped if mmap_min_addr is 0.
>
> Blocking all faults to the first page would potentially break any
> program that does that.
>
> Also if there is something mapped at 0 it's a good chance it is an
> exploit attempt :)
Ok, I see.
In fact, we hit this warning because we don't provide copy_from_kernel_nofault_allowed()
I'll cook a patch for that.
Christophe
prev parent reply other threads:[~2020-12-04 6:31 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-01 10:01 [PATCH] powerpc/mm: Don't see NULL pointer dereference as a KUAP fault Christophe Leroy
2020-12-03 11:55 ` Michael Ellerman
2020-12-04 6:30 ` Christophe Leroy [this message]
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