Minki/linux
1
0
Fork 1
mirror of https://github.com/torvalds/linux.git synced 2024-11-15 08:31:55 +00:00
Code Issues Packages Projects Releases Wiki Activity

KVM: MMU: fix writable sync sp mapping

Browse Source 
While we sync many unsync sp at one time(in mmu_sync_children()),
we may mapping the spte writable, it's dangerous, if one unsync
sp's mapping gfn is another unsync page's gfn.

For example:

SP1.pte[0] = P
SP2.gfn's pfn = P
[SP1.pte[0] = SP2.gfn's pfn]

First, we write protected SP1 and SP2, but SP1 and SP2 are still the
unsync sp.

Then, sync SP1 first, it will detect SP1.pte[0].gfn only has one unsync-sp,
that is SP2, so it will mapping it writable, but we plan to sync SP2 soon,
at this point, the SP2->unsync is not reliable since later we sync SP2 but
SP2->gfn is already writable.

So the final result is: SP2 is the sync page but SP2.gfn is writable.

This bug will corrupt guest's page table, fixed by mark read-only mapping
if the mapped gfn has shadow pages.

Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
This commit is contained in:
Xiao Guangrong 2010-06-30 16:02:02 +08:00 committed by Avi Kivity
parent f5f48ee15c
commit 36a2e6774b
1 changed files with 4 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
arch/x86/kvm/mmu.c
View File

@ -1810,11 +1810,14 @@ static int mmu_need_write_protect(struct kvm_vcpu *vcpu, gfn_t gfn,
bool need_unsync = false;
for_each_gfn_indirect_valid_sp(vcpu->kvm, s, gfn, node) {
if (!can_unsync)
return 1;
if (s->role.level != PT_PAGE_TABLE_LEVEL)
return 1;
if (!need_unsync && !s->unsync) {
if (!can_unsync || !oos_shadow)
if (!oos_shadow)
return 1;
need_unsync = true;
}