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From: Michael Ellerman <mpe@ellerman.id.au>
To: Kees Cook <keescook@chromium.org>
Cc: Balbir Singh <bsingharora@gmail.com>,
	"linuxppc-dev\@ozlabs.org" <linuxppc-dev@ozlabs.org>,
	Bhupesh Sharma <bhsharma@redhat.com>,
	"kernel-hardening\@lists.openwall.com"
	<kernel-hardening@lists.openwall.com>
Subject: Re: [kernel-hardening] Re: [PATCH v2] powerpc/mm: Add support for runtime configuration of ASLR limits
Date: Tue, 25 Apr 2017 08:44:18 +1000	[thread overview]
Message-ID: <87a8752zp9.fsf@concordia.ellerman.id.au> (raw)
In-Reply-To: <CAGXu5jLgCGKfyjP=yW4A_E6vCCtuiKdLeb1f80K6cyxpEA2Y=Q@mail.gmail.com>

Kees Cook <keescook@chromium.org> writes:
> On Mon, Apr 24, 2017 at 7:29 AM, Michael Ellerman <mpe@ellerman.id.au> wrote:
>> Balbir Singh <bsingharora@gmail.com> writes:
>>>> diff --git a/arch/powerpc/mm/mmap.c b/arch/powerpc/mm/mmap.c
>>>> index a5d9ef59debe..6141cfff634e 100644
>>>> --- a/arch/powerpc/mm/mmap.c
>>>> +++ b/arch/powerpc/mm/mmap.c
>>>> @@ -59,13 +59,14 @@ static inline int mmap_is_legacy(void)
>>>>
>>>>  unsigned long arch_mmap_rnd(void)
>>>>  {
>>>> -    unsigned long rnd;
>>>> +    unsigned long shift, rnd;
>>>>
>>>> -    /* 8MB for 32bit, 1GB for 64bit */
>>>> +    shift = mmap_rnd_bits;
>>>> +#ifdef CONFIG_COMPAT
>>>>      if (is_32bit_task())
>>>> -            rnd = get_random_long() % (1<<(23-PAGE_SHIFT));
>>>> -    else
>>>> -            rnd = get_random_long() % (1UL<<(30-PAGE_SHIFT));
>>>> +            shift = mmap_rnd_compat_bits;
>>>> +#endif
>>>> +    rnd = get_random_long() % (1 << shift);
>>>
>>> Nitpick, 1 should be 1UL?
>
> Nice catch!
>
>> No, shift can only be 29 at most IIRC?
>
> The largest value in the kconfigs is 33?

Yeah you're right, for the 4K page kernel it can be 33.

Will fix.

cheers

WARNING: multiple messages have this Message-ID (diff)
From: Michael Ellerman <mpe@ellerman.id.au>
To: Kees Cook <keescook@chromium.org>
Cc: Balbir Singh <bsingharora@gmail.com>,
	"linuxppc-dev@ozlabs.org" <linuxppc-dev@ozlabs.org>,
	Bhupesh Sharma <bhsharma@redhat.com>,
	"kernel-hardening@lists.openwall.com"
	<kernel-hardening@lists.openwall.com>
Subject: Re: [kernel-hardening] Re: [PATCH v2] powerpc/mm: Add support for runtime configuration of ASLR limits
Date: Tue, 25 Apr 2017 08:44:18 +1000	[thread overview]
Message-ID: <87a8752zp9.fsf@concordia.ellerman.id.au> (raw)
In-Reply-To: <CAGXu5jLgCGKfyjP=yW4A_E6vCCtuiKdLeb1f80K6cyxpEA2Y=Q@mail.gmail.com>

Kees Cook <keescook@chromium.org> writes:
> On Mon, Apr 24, 2017 at 7:29 AM, Michael Ellerman <mpe@ellerman.id.au> wrote:
>> Balbir Singh <bsingharora@gmail.com> writes:
>>>> diff --git a/arch/powerpc/mm/mmap.c b/arch/powerpc/mm/mmap.c
>>>> index a5d9ef59debe..6141cfff634e 100644
>>>> --- a/arch/powerpc/mm/mmap.c
>>>> +++ b/arch/powerpc/mm/mmap.c
>>>> @@ -59,13 +59,14 @@ static inline int mmap_is_legacy(void)
>>>>
>>>>  unsigned long arch_mmap_rnd(void)
>>>>  {
>>>> -    unsigned long rnd;
>>>> +    unsigned long shift, rnd;
>>>>
>>>> -    /* 8MB for 32bit, 1GB for 64bit */
>>>> +    shift = mmap_rnd_bits;
>>>> +#ifdef CONFIG_COMPAT
>>>>      if (is_32bit_task())
>>>> -            rnd = get_random_long() % (1<<(23-PAGE_SHIFT));
>>>> -    else
>>>> -            rnd = get_random_long() % (1UL<<(30-PAGE_SHIFT));
>>>> +            shift = mmap_rnd_compat_bits;
>>>> +#endif
>>>> +    rnd = get_random_long() % (1 << shift);
>>>
>>> Nitpick, 1 should be 1UL?
>
> Nice catch!
>
>> No, shift can only be 29 at most IIRC?
>
> The largest value in the kconfigs is 33?

Yeah you're right, for the 4K page kernel it can be 33.

Will fix.

cheers

  reply	other threads:[~2017-04-24 22:44 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-04-20 14:36 [PATCH v2] powerpc/mm: Add support for runtime configuration of ASLR limits Michael Ellerman
2017-04-20 14:36 ` [kernel-hardening] " Michael Ellerman
2017-04-20 20:08 ` Kees Cook
2017-04-20 20:08   ` [kernel-hardening] " Kees Cook
2017-04-21  5:51 ` Aneesh Kumar K.V
2017-04-21  5:51   ` [kernel-hardening] " Aneesh Kumar K.V
2017-04-21  6:49 ` Bhupesh Sharma
2017-04-21  6:49   ` [kernel-hardening] " Bhupesh Sharma
2017-04-23 11:53 ` [v2] " Michael Ellerman
2017-04-23 11:53   ` [kernel-hardening] " Michael Ellerman
2017-04-24  1:02 ` [PATCH v2] " Balbir Singh
2017-04-24  1:02   ` [kernel-hardening] " Balbir Singh
2017-04-24 14:29   ` Michael Ellerman
2017-04-24 17:56     ` Kees Cook
2017-04-24 22:44       ` Michael Ellerman [this message]
2017-04-24 22:44         ` Michael Ellerman
2017-04-25  0:56     ` Balbir Singh

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