From: Michael Ellerman <patch-notifications@ellerman.id.au>
To: Michael Ellerman <mpe@ellerman.id.au>, linuxppc-dev@ozlabs.org
Cc: bhsharma@redhat.com, keescook@chromium.org
Subject: Re: powerpc/mm: Fix possible out-of-bounds shift in arch_mmap_rnd()
Date: Thu, 27 Apr 2017 20:30:54 +1000 (AEST) [thread overview]
Message-ID: <3wDCsC06ZSz9sNS@ozlabs.org> (raw)
In-Reply-To: <1493122181-20921-1-git-send-email-mpe@ellerman.id.au>
On Tue, 2017-04-25 at 12:09:41 UTC, Michael Ellerman wrote:
> The recent patch to add runtime configuration of the ASLR limits added a bug in
> arch_mmap_rnd() where we may shift an integer (32-bits) by up to 33 bits,
> leading to undefined behaviour.
>
> In practice it exhibits as every process seg faulting instantly, presumably
> because the rnd value hasn't been restricited by the modulus at all. We didn't
> notice because it only happens under certain kernel configurations and if the
> number of bits is actually set to a large value.
>
> Fix it by switching to unsigned long.
>
> Fixes: 9fea59bd7ca5 ("powerpc/mm: Add support for runtime configuration of ASLR limits")
> Reported-by: Balbir Singh <bsingharora@gmail.com>
> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
> Reviewed-by: Kees Cook <keescook@chromium.org>
Applied to powerpc next.
https://git.kernel.org/powerpc/c/b409946b2a3c1ddcde75e5f35a77e0
cheers
prev parent reply other threads:[~2017-04-27 10:30 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-04-25 12:09 [PATCH] powerpc/mm: Fix possible out-of-bounds shift in arch_mmap_rnd() Michael Ellerman
2017-04-25 16:08 ` Kees Cook
2017-04-27 10:30 ` Michael Ellerman [this message]
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