Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx> writes:
> On 05/11/2015 10:55 AM, Xiao Guangrong wrote:
>> KVM may turn a user page to a kernel page when kernel writes a readonly
>> user page if CR0.WP = 1. This shadow page entry will be reused after
>> SMAP is enabled so that kernel is allowed to access this user page
>>
>> Fix it by setting SMAP && !CR0.WP into shadow page's role and reset mmu
>> once CR4.SMAP is updated
>>
>> Signed-off-by: Xiao Guangrong <guangrong.xiao@xxxxxxxxxxxxxxx>
>> ---
>
>
>>
>> @@ -4208,12 +4211,18 @@ void kvm_mmu_pte_write(struct kvm_vcpu *vcpu, gpa_t gpa,
>> const u8 *new, int bytes)
>> {
>> gfn_t gfn = gpa >> PAGE_SHIFT;
>> - union kvm_mmu_page_role mask = { .word = 0 };
>> struct kvm_mmu_page *sp;
>> LIST_HEAD(invalid_list);
>> u64 entry, gentry, *spte;
>> int npte;
>> bool remote_flush, local_flush, zap_page;
>> + union kvm_mmu_page_role mask = (union kvm_mmu_page_role) {
>> + .cr0_wp = 1,
>> + .cr4_pae = 1,
>> + .nxe = 1,
>> + .smep_andnot_wp = 1,
>> + .smap_andnot_wp = 1,
>> + };
>>
>>
>
>
> This breaks older compilers that can't initialize anon structures.
How old ? Even gcc 3.1 says you can use unnamed struct/union fields and
3.2 is the minimum version required to compile the kernel as mentioned
in the README.
We could simply just name the structure, but I doubt this is the
only place in the kernel code where it's being used this way :)
Bandan
> -boris
> --
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