Le 27/01/2022 à 13:37, Kefeng Wang a écrit :
> When run ethtool eth0 on PowerPC64, 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, let's check the virt addr above PAGE_OFFSET in
> the virt_addr_valid() for PowerPC64, which will make sure that the passed
> address is a valid linear map address.
>
> Meanwhile, PAGE_OFFSET is the virtual address of the start of lowmem,
> the check is suitable for PowerPC32 too.
>
> Signed-off-by: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx>
Reviewed-by: Christophe Leroy <christophe.leroy@xxxxxxxxxx>
> ---
> v3:
> - update changelog and remove a redundant cast
> 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..a8a29a23ce2d 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; \
> + _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
