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Date: Sat, 18 Feb 2017 20:32:52 +1100
From: Michael Ellerman <mpe@...erman.id.au>
To: Kees Cook <keescook@...omium.org>, Geert Uytterhoeven <geert@...ux-m68k.org>
Cc: "linux-kernel\@vger.kernel.org" <linux-kernel@...r.kernel.org>, Hoeun Ryu <hoeun.ryu@...il.com>, "kernel-hardening\@lists.openwall.com" <kernel-hardening@...ts.openwall.com>
Subject: Re: Re: [PATCH] usercopy: Add tests for all get_user() sizes
Kees Cook <keescook@...omium.org> writes:
> On Wed, Feb 15, 2017 at 12:50 AM, Geert Uytterhoeven
> <geert@...ux-m68k.org> wrote:
>> On Tue, Feb 14, 2017 at 9:40 PM, Kees Cook <keescook@...omium.org> wrote:
>>> The existing test was only exercising native unsigned long size
>>> get_user(). For completeness, we should check all sizes.
>>>
>>> Signed-off-by: Kees Cook <keescook@...omium.org>
>>> ---
>>> lib/test_user_copy.c | 45 ++++++++++++++++++++++++++++++++++-----------
>>> 1 file changed, 34 insertions(+), 11 deletions(-)
>>>
>>> diff --git a/lib/test_user_copy.c b/lib/test_user_copy.c
>>> index ac3a60ba9331..49569125b7c5 100644
>>> --- a/lib/test_user_copy.c
>>> +++ b/lib/test_user_copy.c
>>> @@ -40,8 +40,11 @@ static int __init test_user_copy_init(void)
>>> char __user *usermem;
>>> char *bad_usermem;
>>> unsigned long user_addr;
>>> - unsigned long value = 0x5A;
>>> char *zerokmem;
>>> + u8 val_u8;
>>> + u16 val_u16;
>>> + u32 val_u32;
>>> + u64 val_u64;
>>>
>>> kmem = kmalloc(PAGE_SIZE * 2, GFP_KERNEL);
>>> if (!kmem)
>>> @@ -72,10 +75,20 @@ static int __init test_user_copy_init(void)
>>> "legitimate copy_from_user failed");
>>> ret |= test(copy_to_user(usermem, kmem, PAGE_SIZE),
>>> "legitimate copy_to_user failed");
>>> - ret |= test(get_user(value, (unsigned long __user *)usermem),
>>> - "legitimate get_user failed");
>>> - ret |= test(put_user(value, (unsigned long __user *)usermem),
>>> - "legitimate put_user failed");
>>> +
>>> +#define test_legit(size) \
>>> + do { \
>>> + ret |= test(get_user(val_##size, (size __user *)usermem), \
>>> + "legitimate get_user (" #size ") failed"); \
>>> + ret |= test(put_user(val_##size, (size __user *)usermem), \
>>> + "legitimate put_user (" #size ") failed"); \
>>> + } while (0)
>>> +
>>> + test_legit(u8);
>>> + test_legit(u16);
>>> + test_legit(u32);
>>> + test_legit(u64);
>>> +#undef test_legit
>>
>> ERROR: "__get_user_bad" [lib/test_user_copy.ko] undefined!
>>
>> http://kisskb.ellerman.id.au/kisskb/buildresult/12936728/
>>
>> So 64-bit get_user() support is mandatory now?
>
> That's not my intention. :) In my sampling of architectures, I missed
> a couple 32-bit archs that don't support 64-bit getuser(). I'm not
> sure how to correctly write these tests, though, since it seems rather
> ad-hoc. e.g. m68k has 64-bit getuser() commented out due to an old gcc
> bug...
>
> Should I just universally skip 64-bit getuser on 32-bit archs?
I think you should just make it opt-in for 32-bit arches.
cheers
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