Re: [PATCH v2 1/2] powerpc: Fix virt_addr_valid() check
Le 19/01/2022 à 02:15, Kefeng Wang a écrit : > > On 2022/1/11 14:04, Christophe Leroy wrote: >> >> Le 11/01/2022 à 05:37, Nicholas Piggin a écrit : >>> Excerpts from Kefeng Wang's message of January 8, 2022 9:58 pm: Hi PPC maintainers， ping.. >>> Hmm. I might have confused myself about this. I'm going back and >>> trying to work out what I was thinking when I suggested it. This >>> works on 64e because vmalloc space is below the kernel linear map, >>> right? >>> >>> On 64s it is the other way around and it is still possible to enable >>> flatmem on 64s. Altough we might just not hit the problem there because >>> __pa() will not mask away the vmalloc offset for 64s so it will still >>> return something that's outside the pfn_valid range for flatmem. That's >>> very subtle though. >> That's the way it works on PPC32 at least, so for me it's not chocking >> to have it work the same way on PPC64s. >> >> The main issue here is the way __pa() works. On PPC32 __pa = va - >> PAGE_OFFSET, so it works correctly for any address. >> On PPC64, __pa() works by masking out the 2 top bits instead of >> substracting PAGE_OFFSET, so the test must add a verification that we >> really have the 2 top bits set at first. This is what (addr >= >> PAGE_OFFSET) does. Once this first test is done, we can perfectly rely >> on pfn_valid() just like PPC32, I see absolutely no point in an >> additionnal test checking the addr is below KERN_VIRT_START. > > > Hi Christophe and Nicholas， for ppc32， I think we need check the upper > limit, Why ? Have you experimented any problem at all on PPC32 with the way it is done at the moment ? I don't think we have to change PPC32 at all unless we have a real reason to do it. > > eg, addr >= PAGE_OFFSET && addr < high_memory Isn't it exactly what pfn_valid() already do today ? Why change that at all ? Christophe > > arch/powerpc/mm/mem.c: high_memory = (void *) __va(max_low_pfn * > PAGE_SIZE); > > for ppc32 max_low_pfn is the upper low memory pfn, and For ppc64, > high_memory is > > the max memory pfn, it looks good too, correct me if I'm wrong, if the > above check > > is ok, I will send a new v3, thanks. > > > > >> >> >>> The checks added to __pa actually don't prevent vmalloc memory from >>> being passed to it either on 64s, only a more basic test. >> That's correct. It is the role of pfn_valid() to check that. >> >> Christophe >> >>> I think 64s wants (addr >= PAGE_OFFSET && addr < KERN_VIRT_START) as >>> the condition. Could possibly add that check to __pa as well to >>> catch vmalloc addresses. >>> >>> Thanks, >>> Nick >>> >>>
Re: [PATCH v2 1/2] powerpc: Fix virt_addr_valid() check
Le 11/01/2022 à 05:37, Nicholas Piggin a écrit :
> Excerpts from Kefeng Wang's message of January 8, 2022 9:58 pm:
>> Hi PPC maintainers， ping..
>
> Hmm. I might have confused myself about this. I'm going back and
> trying to work out what I was thinking when I suggested it. This
> works on 64e because vmalloc space is below the kernel linear map,
> right?
>
> On 64s it is the other way around and it is still possible to enable
> flatmem on 64s. Altough we might just not hit the problem there because
> __pa() will not mask away the vmalloc offset for 64s so it will still
> return something that's outside the pfn_valid range for flatmem. That's
> very subtle though.
That's the way it works on PPC32 at least, so for me it's not chocking
to have it work the same way on PPC64s.
The main issue here is the way __pa() works. On PPC32 __pa = va -
PAGE_OFFSET, so it works correctly for any address.
On PPC64, __pa() works by masking out the 2 top bits instead of
substracting PAGE_OFFSET, so the test must add a verification that we
really have the 2 top bits set at first. This is what (addr >=
PAGE_OFFSET) does. Once this first test is done, we can perfectly rely
on pfn_valid() just like PPC32, I see absolutely no point in an
additionnal test checking the addr is below KERN_VIRT_START.
>
> The checks added to __pa actually don't prevent vmalloc memory from
> being passed to it either on 64s, only a more basic test.
That's correct. It is the role of pfn_valid() to check that.
Christophe
>
> I think 64s wants (addr >= PAGE_OFFSET && addr < KERN_VIRT_START) as
> the condition. Could possibly add that check to __pa as well to
> catch vmalloc addresses.
>
> Thanks,
> Nick
>
>>
>> On 2021/12/25 20:06, Kefeng Wang wrote:
>>> When run ethtool eth0, the BUG occurred,
>>>
>>> usercopy: Kernel memory exposure attempt detected from SLUB object not
>>> in SLUB page?! (offset 0, size 1048)!
>>> kernel BUG at mm/usercopy.c:99
>>> ...
>>> usercopy_abort+0x64/0xa0 (unreliable)
>>> __check_heap_object+0x168/0x190
>>> __check_object_size+0x1a0/0x200
>>> dev_ethtool+0x2494/0x2b20
>>> dev_ioctl+0x5d0/0x770
>>> sock_do_ioctl+0xf0/0x1d0
>>> sock_ioctl+0x3ec/0x5a0
>>> __se_sys_ioctl+0xf0/0x160
>>> system_call_exception+0xfc/0x1f0
>>> system_call_common+0xf8/0x200
>>>
>>> The code shows below,
>>>
>>> data = vzalloc(array_size(gstrings.len, ETH_GSTRING_LEN));
>>> copy_to_user(useraddr, data, gstrings.len * ETH_GSTRING_LEN))
>>>
>>> The data is alloced by vmalloc(), virt_addr_valid(ptr) will return true
>>> on PowerPC64, which leads to the panic.
>>>
>>> As commit 4dd7554a6456 ("powerpc/64: Add VIRTUAL_BUG_ON checks for __va
>>> and __pa addresses") does, make sure the virt addr above PAGE_OFFSET in
>>> the virt_addr_valid().
>>>
>>> Signed-off-by: Kefeng Wang
>>> ---
>>>arch/powerpc/include/asm/page.h | 5 -
>>>1 file changed, 4 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/arch/powerpc/include/asm/page.h
>>> b/arch/powerpc/include/asm/page.h
>>> index 254687258f42..300d4c105a3a 100644
>>> --- a/arch/powerpc/include/asm/page.h
>>> +++ b/arch/powerpc/include/asm/page.h
>>> @@ -132,7 +132,10 @@ static inline bool pfn_valid(unsigned long pfn)
>>>#define virt_to_page(kaddr) pfn_to_page(virt_to_pfn(kaddr))
>>>#define pfn_to_kaddr(pfn)__va((pfn) << PAGE_SHIFT)
>>>
>>> -#define virt_addr_valid(kaddr) pfn_valid(virt_to_pfn(kaddr))
>>> +#define virt_addr_valid(vaddr) ({
>>> \
>>> + unsigned long _addr = (unsigned long)vaddr;
>>> \
>>> + (unsigned long)(_addr) >= PAGE_OFFSET && pfn_valid(virt_to_pfn(_addr));
>>> \
>>> +})
>>>
>>>/*
>>> * On Book-E parts we need __va to parse the device tree and we can't
>>
Re: [PATCH v2 1/2] powerpc: Fix virt_addr_valid() check
Excerpts from Kefeng Wang's message of January 8, 2022 9:58 pm:
> Hi PPC maintainers， ping..
Hmm. I might have confused myself about this. I'm going back and
trying to work out what I was thinking when I suggested it. This
works on 64e because vmalloc space is below the kernel linear map,
right?
On 64s it is the other way around and it is still possible to enable
flatmem on 64s. Altough we might just not hit the problem there because
__pa() will not mask away the vmalloc offset for 64s so it will still
return something that's outside the pfn_valid range for flatmem. That's
very subtle though.
The checks added to __pa actually don't prevent vmalloc memory from
being passed to it either on 64s, only a more basic test.
I think 64s wants (addr >= PAGE_OFFSET && addr < KERN_VIRT_START) as
the condition. Could possibly add that check to __pa as well to
catch vmalloc addresses.
Thanks,
Nick
>
> On 2021/12/25 20:06, Kefeng Wang wrote:
>> When run ethtool eth0, the BUG occurred,
>>
>>usercopy: Kernel memory exposure attempt detected from SLUB object not in
>> SLUB page?! (offset 0, size 1048)!
>>kernel BUG at mm/usercopy.c:99
>>...
>>usercopy_abort+0x64/0xa0 (unreliable)
>>__check_heap_object+0x168/0x190
>>__check_object_size+0x1a0/0x200
>>dev_ethtool+0x2494/0x2b20
>>dev_ioctl+0x5d0/0x770
>>sock_do_ioctl+0xf0/0x1d0
>>sock_ioctl+0x3ec/0x5a0
>>__se_sys_ioctl+0xf0/0x160
>>system_call_exception+0xfc/0x1f0
>>system_call_common+0xf8/0x200
>>
>> The code shows below,
>>
>>data = vzalloc(array_size(gstrings.len, ETH_GSTRING_LEN));
>>copy_to_user(useraddr, data, gstrings.len * ETH_GSTRING_LEN))
>>
>> The data is alloced by vmalloc(), virt_addr_valid(ptr) will return true
>> on PowerPC64, which leads to the panic.
>>
>> As commit 4dd7554a6456 ("powerpc/64: Add VIRTUAL_BUG_ON checks for __va
>> and __pa addresses") does, make sure the virt addr above PAGE_OFFSET in
>> the virt_addr_valid().
>>
>> Signed-off-by: Kefeng Wang
>> ---
>> arch/powerpc/include/asm/page.h | 5 -
>> 1 file changed, 4 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/powerpc/include/asm/page.h
>> b/arch/powerpc/include/asm/page.h
>> index 254687258f42..300d4c105a3a 100644
>> --- a/arch/powerpc/include/asm/page.h
>> +++ b/arch/powerpc/include/asm/page.h
>> @@ -132,7 +132,10 @@ static inline bool pfn_valid(unsigned long pfn)
>> #define virt_to_page(kaddr)pfn_to_page(virt_to_pfn(kaddr))
>> #define pfn_to_kaddr(pfn) __va((pfn) << PAGE_SHIFT)
>>
>> -#define virt_addr_valid(kaddr) pfn_valid(virt_to_pfn(kaddr))
>> +#define virt_addr_valid(vaddr) ({
>> \
>> +unsigned long _addr = (unsigned long)vaddr;
>> \
>> +(unsigned long)(_addr) >= PAGE_OFFSET && pfn_valid(virt_to_pfn(_addr));
>> \
>> +})
>>
>> /*
>>* On Book-E parts we need __va to parse the device tree and we can't
>
Re: [PATCH v2 1/2] powerpc: Fix virt_addr_valid() check
Le 25/12/2021 à 13:06, Kefeng Wang a écrit :
> When run ethtool eth0, the BUG occurred,
>
>usercopy: Kernel memory exposure attempt detected from SLUB object not in
> SLUB page?! (offset 0, size 1048)!
>kernel BUG at mm/usercopy.c:99
>...
>usercopy_abort+0x64/0xa0 (unreliable)
>__check_heap_object+0x168/0x190
>__check_object_size+0x1a0/0x200
>dev_ethtool+0x2494/0x2b20
>dev_ioctl+0x5d0/0x770
>sock_do_ioctl+0xf0/0x1d0
>sock_ioctl+0x3ec/0x5a0
>__se_sys_ioctl+0xf0/0x160
>system_call_exception+0xfc/0x1f0
>system_call_common+0xf8/0x200
>
> The code shows below,
>
>data = vzalloc(array_size(gstrings.len, ETH_GSTRING_LEN));
>copy_to_user(useraddr, data, gstrings.len * ETH_GSTRING_LEN))
>
> The data is alloced by vmalloc(), virt_addr_valid(ptr) will return true
> on PowerPC64, which leads to the panic.
>
> As commit 4dd7554a6456 ("powerpc/64: Add VIRTUAL_BUG_ON checks for __va
> and __pa addresses") does, make sure the virt addr above PAGE_OFFSET in
> the virt_addr_valid().
The change done by that commit only applies to PPC64.
The change you are doing applies to both PPC64 and PPC32. Did you verify
the impact (or should I say the absence of impact) on PPC32 ?
>
> Signed-off-by: Kefeng Wang
> ---
> arch/powerpc/include/asm/page.h | 5 -
> 1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/arch/powerpc/include/asm/page.h b/arch/powerpc/include/asm/page.h
> index 254687258f42..300d4c105a3a 100644
> --- a/arch/powerpc/include/asm/page.h
> +++ b/arch/powerpc/include/asm/page.h
> @@ -132,7 +132,10 @@ static inline bool pfn_valid(unsigned long pfn)
> #define virt_to_page(kaddr) pfn_to_page(virt_to_pfn(kaddr))
> #define pfn_to_kaddr(pfn) __va((pfn) << PAGE_SHIFT)
>
> -#define virt_addr_valid(kaddr) pfn_valid(virt_to_pfn(kaddr))
> +#define virt_addr_valid(vaddr) ({
> \
> + unsigned long _addr = (unsigned long)vaddr;
> \
> + (unsigned long)(_addr) >= PAGE_OFFSET && pfn_valid(virt_to_pfn(_addr));
> \
_addr is already an 'unsigned long' so you shouldnt need to cast it.
> +})
>
> /*
>* On Book-E parts we need __va to parse the device tree and we can't
