Patch "KVM: MMU: fix smap permission check" has been added to the 4.0-stable tree

This is a note to let you know that I've just added the patch titled

KVM: MMU: fix smap permission check

to the 4.0-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
kvm-mmu-fix-smap-permission-check.patch
and it can be found in the queue-4.0 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Xiao Guangrong <[email protected]>
Date: Thu, 7 May 2015 16:20:15 +0800
Subject: KVM: MMU: fix smap permission check

From: Xiao Guangrong <[email protected]>

commit 7cbeed9bce7580479bb97457dad220cb3594b875 upstream.

Current permission check assumes that RSVD bit in PFEC is always zero, however, it is not true since MMIO #PF will use it to quickly identify MMIO access

Fix it by clearing the bit if walking guest page table is needed

---
 arch/x86/kvm/mmu.h         |    2 ++
 arch/x86/kvm/paging_tmpl.h |    7 +++++++
 2 files changed, 9 insertions(+)

@@ -166,6 +166,8 @@ static inline bool permission_fault(stru
 	int index = (pfec >> 1) +
 		    (smap >> (X86_EFLAGS_AC_BIT - PFERR_RSVD_BIT + 1));
 
+	WARN_ON(pfec & PFERR_RSVD_MASK);
+
 	return (mmu->permissions[index] >> pte_access) & 1;
 }
 

@@ -718,6 +718,13 @@ static int FNAME(page_fault)(struct kvm_
 					      mmu_is_nested(vcpu));
 		if (likely(r != RET_MMIO_PF_INVALID))
 			return r;
+
+		/*
+		 * page fault with PFEC.RSVD  = 1 is caused by shadow
+		 * page fault, should not be used to walk guest page
+		 * table.
+		 */
+		error_code &= ~PFERR_RSVD_MASK;
 	};
 
 	r = mmu_topup_memory_caches(vcpu);

Patches currently in stable-queue which might be from [email protected] are

queue-4.0/kvm-mmu-fix-smap-permission-check.patch queue-4.0/kvm-mmu-fix-cr4.smep-1-cr0.wp-0-with-shadow-pages.patch queue-4.0/kvm-mmu-fix-smap-virtualization.patch