Le 24/12/2021 à 08:06, Kefeng Wang a écrit :
>
> On 2021/12/24 14:01, Christophe Leroy wrote:
>>
>> Le 23/12/2021 à 11:21, Kefeng Wang a écrit :
>>> This reverts commit 517e1fbeb65f5eade8d14f46ac365db6c75aea9b.
>>>
>>> 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
>>>
>>> When run ethtool eth0, the BUG occurred, 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, add back the
>>> is_vmalloc_or_module()
>>> check to fix it.
>> Is it expected that virt_addr_valid() returns true on PPC64 for
>> vmalloc'ed memory ? If that's the case it also means that
>> CONFIG_DEBUG_VIRTUAL won't work as expected either.
>
> Our product reports this bug to me, after let them do some test,
>
> I found virt_addr_valid return true for vmalloc'ed memory on their board.
>
> I think DEBUG_VIRTUAL could not be work well too, but I can't test it.
>
>>
>> If it is unexpected, I think you should fix PPC64 instead of adding this
>> hack back. Maybe the ARM64 fix can be used as a starting point, see
>> commit 68dd8ef32162 ("arm64: memory: Fix virt_addr_valid() using
>> __is_lm_address()")
>
> Yes， I check the history, fix virt_addr_valid() on PowerPC is what I
> firstly want to do,
>
> but I am not familiar with PPC, and also HARDENED_USERCOPY on other's
> ARCHs could
>
> has this issue too, so I add the workaround back.
>
>
> 1) PPC maintainer/expert, any suggestion ?
>
> 2) Maybe we could add some check to WARN this scenario.
>
> --- a/mm/usercopy.c
> +++ b/mm/usercopy.c
> @@ -229,6 +229,8 @@ static inline void check_heap_object(const void
> *ptr, unsigned long n,
> if (!virt_addr_valid(ptr))
> return;
>
> + WARN_ON_ONCE(is_vmalloc_or_module_addr(ptr));
>
>> In the meantime, can you provide more information on your config,
>> especially which memory model is used ?
>
> Some useful configs,
>
> CONFIG_PPC64=y
> CONFIG_PPC_BOOK3E_64=y
> CONFIG_E5500_CPU=y
> CONFIG_TARGET_CPU_BOOL=y
> CONFIG_PPC_BOOK3E=y
> CONFIG_E500=y
> CONFIG_PPC_E500MC=y
> CONFIG_PPC_FPU=y
> CONFIG_FSL_EMB_PERFMON=y
> CONFIG_FSL_EMB_PERF_EVENT=y
> CONFIG_FSL_EMB_PERF_EVENT_E500=y
> CONFIG_BOOKE=y
> CONFIG_PPC_FSL_BOOK3E=y
> CONFIG_PTE_64BIT=y
> CONFIG_PHYS_64BIT=y
> CONFIG_PPC_MMU_NOHASH=y
> CONFIG_PPC_BOOK3E_MMU=y
> CONFIG_SELECT_MEMORY_MODEL=y
> CONFIG_FLATMEM_MANUAL=y
> CONFIG_FLATMEM=y
> CONFIG_FLAT_NODE_MEM_MAP=y
> CONFIG_SPARSEMEM_VMEMMAP_ENABLE=y
>
OK so it is PPC64 book3e and with flatmem.
The problem is virt_to_pfn() which uses __pa()
__pa(x) on PPC64 is (x) & 0x0fffffffffffffffUL
And on book3e/64 we have
VMALLOC_START = KERN_VIRT_START = ASM_CONST(0x8000000000000000)
It means that __pa() will return a valid PFN for VMALLOCed addresses.
So an additional check is required in virt_addr_valid(), maybe check
that (kaddr & PAGE_OFFSET) == PAGE_OFFSET
Can you try that ?
#define virt_addr_valid(kaddr) ((kaddr & PAGE_OFFSET) == PAGE_OFFSET &&
pfn_valid(virt_to_pfn(kaddr)))
Thanks
Christophe
