linux-kernel - [16/45] KVM: MMU: fix direct sps access corrupted

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20101119214410.741293356@clark.site>
Date:	Fri, 19 Nov 2010 13:42:56 -0800
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...nel.org, greg@...ah.com
Cc:	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Xiao Guangrong <xiaoguangrong@...fujitsu.com>,
	Marcelo Tosatti <mtosatti@...hat.com>
Subject: [16/45] KVM: MMU: fix direct sps access corrupted

2.6.32-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Xiao Guangrong <xiaoguangrong@...fujitsu.com>

commit 9e7b0e7fba45ca3c6357aeb7091ebc281f1de365 upstream.

If the mapping is writable but the dirty flag is not set, we will find
the read-only direct sp and setup the mapping, then if the write #PF
occur, we will mark this mapping writable in the read-only direct sp,
now, other real read-only mapping will happily write it without #PF.

It may hurt guest's COW

Fixed by re-install the mapping when write #PF occur.

Signed-off-by: Xiao Guangrong <xiaoguangrong@...fujitsu.com>
Signed-off-by: Marcelo Tosatti <mtosatti@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

---
 arch/x86/kvm/paging_tmpl.h |   28 ++++++++++++++++++++++++++--
 1 file changed, 26 insertions(+), 2 deletions(-)

--- a/arch/x86/kvm/paging_tmpl.h
+++ b/arch/x86/kvm/paging_tmpl.h
@@ -318,8 +318,32 @@ static u64 *FNAME(fetch)(struct kvm_vcpu
 			break;
 		}
 
-		if (is_shadow_present_pte(*sptep) && !is_large_pte(*sptep))
-			continue;
+		if (is_shadow_present_pte(*sptep) && !is_large_pte(*sptep)) {
+			struct kvm_mmu_page *child;
+			unsigned direct_access;
+
+			if (level != gw->level)
+				continue;
+
+			/*
+			 * For the direct sp, if the guest pte's dirty bit
+			 * changed form clean to dirty, it will corrupt the
+			 * sp's access: allow writable in the read-only sp,
+			 * so we should update the spte at this point to get
+			 * a new sp with the correct access.
+			 */
+			direct_access = gw->pt_access & gw->pte_access;
+			if (!is_dirty_gpte(gw->ptes[gw->level - 1]))
+				direct_access &= ~ACC_WRITE_MASK;
+
+			child = page_header(*sptep & PT64_BASE_ADDR_MASK);
+			if (child->role.access == direct_access)
+				continue;
+
+			mmu_page_remove_parent_pte(child, sptep);
+			__set_spte(sptep, shadow_trap_nonpresent_pte);
+			kvm_flush_remote_tlbs(vcpu->kvm);
+		}
 
 		if (is_large_pte(*sptep)) {
 			rmap_remove(vcpu->kvm, sptep);


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/