linux-kernel - [PATCH 3.14 02/19] KVM: PPC: Book3S HV: Sanitize special-purpose register values on guest exit

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]

Date:	Mon, 14 Mar 2016 10:52:42 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Thomas Huth <thuth@...hat.com>,
	David Gibson <david@...son.dropbear.id.au>,
	Paul Mackerras <paulus@...ba.org>
Subject: [PATCH 3.14 02/19] KVM: PPC: Book3S HV: Sanitize special-purpose register values on guest exit

3.14-stable review patch.  If anyone has any objections, please let me know.

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

From: Paul Mackerras <paulus@...ba.org>

commit ccec44563b18a0ce90e2d4f332784b3cb25c8e9c upstream.

Thomas Huth discovered that a guest could cause a hard hang of a
host CPU by setting the Instruction Authority Mask Register (IAMR)
to a suitable value.  It turns out that this is because when the
code was added to context-switch the new special-purpose registers
(SPRs) that were added in POWER8, we forgot to add code to ensure
that they were restored to a sane value on guest exit.

This adds code to set those registers where a bad value could
compromise the execution of the host kernel to a suitable neutral
value on guest exit.

Fixes: b005255e12a3
Reported-by: Thomas Huth <thuth@...hat.com>
Reviewed-by: David Gibson <david@...son.dropbear.id.au>
Signed-off-by: Paul Mackerras <paulus@...ba.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/powerpc/kvm/book3s_hv_rmhandlers.S |   14 ++++++++++++++
 1 file changed, 14 insertions(+)

--- a/arch/powerpc/kvm/book3s_hv_rmhandlers.S
+++ b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
@@ -1148,6 +1148,20 @@ END_FTR_SECTION_IFCLR(CPU_FTR_ARCH_207S)
 	std	r6, VCPU_ACOP(r9)
 	stw	r7, VCPU_GUEST_PID(r9)
 	std	r8, VCPU_WORT(r9)
+	/*
+	 * Restore various registers to 0, where non-zero values
+	 * set by the guest could disrupt the host.
+	 */
+	li	r0, 0
+	mtspr	SPRN_IAMR, r0
+	mtspr	SPRN_CIABR, r0
+	mtspr	SPRN_DAWRX, r0
+	mtspr	SPRN_TCSCR, r0
+	mtspr	SPRN_WORT, r0
+	/* Set MMCRS to 1<<31 to freeze and disable the SPMC counters */
+	li	r0, 1
+	sldi	r0, r0, 31
+	mtspr	SPRN_MMCRS, r0
 8:
 
 	/* Save and reset AMR and UAMOR before turning on the MMU */