[PATCH 3.13.y-ckt 20/48] powerpc/mm: Recompute hash value after a failed update

From	Kamal Mostafa <kamal@canonical.com>
Newsgroups	linux.kernel
Subject	[PATCH 3.13.y-ckt 20/48] powerpc/mm: Recompute hash value after a failed update
Date	2015-10-27 22:50 +0100
Message-ID	<qokhZ-21H-63@gated-at.bofh.it> (permalink)
References	<qok8h-1XT-3@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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3.13.11-ckt29 -stable review patch.  If anyone has any objections, please let me know.

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

From: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>

commit 36b35d5d807b7e57aff7d08e63de8b17731ee211 upstream.

If we had secondary hash flag set, we ended up modifying hash value in
the updatepp code path. Hence with a failed updatepp we will be using
a wrong hash value for the following hash insert. Fix this by
recomputing hash before insert.

Without this patch we can end up with using wrong slot number in linux
pte. That can result in us missing an hash pte update or invalidate
which can cause memory corruption or even machine check.

Fixes: 6d492ecc6489 ("powerpc/THP: Add code to handle HPTE faults for hugepages")
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Reviewed-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
---
 arch/powerpc/mm/hugepage-hash64.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/mm/hugepage-hash64.c b/arch/powerpc/mm/hugepage-hash64.c
index 7d86c86..9836e80 100644
--- a/arch/powerpc/mm/hugepage-hash64.c
+++ b/arch/powerpc/mm/hugepage-hash64.c
@@ -136,7 +136,6 @@ int __hash_page_thp(unsigned long ea, unsigned long access, unsigned long vsid,
 	BUG_ON(index >= 4096);
 
 	vpn = hpt_vpn(ea, vsid, ssize);
-	hash = hpt_hash(vpn, shift, ssize);
 	hpte_slot_array = get_hpte_slot_array(pmdp);
 	if (psize == MMU_PAGE_4K) {
 		/*
@@ -151,6 +150,7 @@ int __hash_page_thp(unsigned long ea, unsigned long access, unsigned long vsid,
 	valid = hpte_valid(hpte_slot_array, index);
 	if (valid) {
 		/* update the hpte bits */
+		hash = hpt_hash(vpn, shift, ssize);
 		hidx =  hpte_hash_index(hpte_slot_array, index);
 		if (hidx & _PTEIDX_SECONDARY)
 			hash = ~hash;
@@ -176,6 +176,7 @@ int __hash_page_thp(unsigned long ea, unsigned long access, unsigned long vsid,
 	if (!valid) {
 		unsigned long hpte_group;
 
+		hash = hpt_hash(vpn, shift, ssize);
 		/* insert new entry */
 		pa = pmd_pfn(__pmd(old_pmd)) << PAGE_SHIFT;
 		new_pmd |= _PAGE_HASHPTE;
-- 
1.9.1

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Thread

[3.13.y-ckt stable] Linux 3.13.11-ckt29 stable review Kamal Mostafa <kamal@canonical.com> - 2015-10-27 22:40 +0100
  [PATCH 3.13.y-ckt 27/48] usb: Use the USB_SS_MULT() macro to get the burst multiplier. Kamal Mostafa <kamal@canonical.com> - 2015-10-27 22:50 +0100
  [PATCH 3.13.y-ckt 16/48] arm64: head.S: initialise mdcr_el2 in el2_setup Kamal Mostafa <kamal@canonical.com> - 2015-10-27 22:50 +0100
  [PATCH 3.13.y-ckt 21/48] x86/platform: Fix Geode LX timekeeping in the generic x86 build Kamal Mostafa <kamal@canonical.com> - 2015-10-27 22:50 +0100
  [PATCH 3.13.y-ckt 07/48] spi: Fix documentation of spi_alloc_master() Kamal Mostafa <kamal@canonical.com> - 2015-10-27 22:50 +0100
  [PATCH 3.13.y-ckt 23/48] arm64: errata: add module build workaround for erratum #843419 Kamal Mostafa <kamal@canonical.com> - 2015-10-27 22:50 +0100
  [PATCH 3.13.y-ckt 03/48] KEYS: Fix crash when attempt to garbage collect an uninstantiated keyring Kamal Mostafa <kamal@canonical.com> - 2015-10-27 22:50 +0100
  [PATCH 3.13.y-ckt 15/48] btrfs: skip waiting on ordered range for special files Kamal Mostafa <kamal@canonical.com> - 2015-10-27 22:50 +0100
  [PATCH 3.13.y-ckt 29/48] usb: xhci: Clear XHCI_STATE_DYING on start Kamal Mostafa <kamal@canonical.com> - 2015-10-27 22:50 +0100
  [PATCH 3.13.y-ckt 24/48] arm64: KVM: Disable virtual timer even if the guest is not using it Kamal Mostafa <kamal@canonical.com> - 2015-10-27 22:50 +0100
  [PATCH 3.13.y-ckt 28/48] xhci: give command abortion one more chance before killing xhci Kamal Mostafa <kamal@canonical.com> - 2015-10-27 22:50 +0100
  [PATCH 3.13.y-ckt 18/48] iser-target: remove command with state ISTATE_REMOVE Kamal Mostafa <kamal@canonical.com> - 2015-10-27 22:50 +0100
  [PATCH 3.13.y-ckt 26/48] KVM: x86: trap AMD MSRs for the TSeg base and mask Kamal Mostafa <kamal@canonical.com> - 2015-10-27 22:50 +0100
  [PATCH 3.13.y-ckt 12/48] USB: option: add ZTE PIDs Kamal Mostafa <kamal@canonical.com> - 2015-10-27 22:50 +0100
  [PATCH 3.13.y-ckt 05/48] [stable-only] net: add length argument to skb_copy_and_csum_datagram_iovec Kamal Mostafa <kamal@canonical.com> - 2015-10-27 22:50 +0100
  [PATCH 3.13.y-ckt 11/48] hwmon: (nct6775) Swap STEP_UP_TIME and STEP_DOWN_TIME registers for most chips Kamal Mostafa <kamal@canonical.com> - 2015-10-27 22:50 +0100
  [PATCH 3.13.y-ckt 14/48] Btrfs: fix read corruption of compressed and shared extents Kamal Mostafa <kamal@canonical.com> - 2015-10-27 22:50 +0100
  [PATCH 3.13.y-ckt 04/48] KEYS: Don't permit request_key() to construct a new keyring Kamal Mostafa <kamal@canonical.com> - 2015-10-27 22:50 +0100
  [PATCH 3.13.y-ckt 25/48] arm: KVM: Disable virtual timer even if the guest is not using it Kamal Mostafa <kamal@canonical.com> - 2015-10-27 22:50 +0100
  [PATCH 3.13.y-ckt 06/48] spi: spi-pxa2xx: Check status register to determine if SSSR_TINT is disabled Kamal Mostafa <kamal@canonical.com> - 2015-10-27 22:50 +0100
  [PATCH 3.13.y-ckt 20/48] powerpc/mm: Recompute hash value after a failed update Kamal Mostafa <kamal@canonical.com> - 2015-10-27 22:50 +0100
  [PATCH 3.13.y-ckt 10/48] CIFS: fix type confusion in copy offload ioctl Kamal Mostafa <kamal@canonical.com> - 2015-10-27 22:50 +0100
  [PATCH 3.13.y-ckt 08/48] ARM: 8429/1: disable GCC SRA optimization Kamal Mostafa <kamal@canonical.com> - 2015-10-27 22:50 +0100
  [PATCH 3.13.y-ckt 02/48] KEYS: Fix race between key destruction and finding a keyring by name Kamal Mostafa <kamal@canonical.com> - 2015-10-27 22:50 +0100
  [PATCH 3.13.y-ckt 09/48] powerpc/MSI: Fix race condition in tearing down MSI interrupts Kamal Mostafa <kamal@canonical.com> - 2015-10-27 22:50 +0100
  [PATCH 3.13.y-ckt 13/48] x86/apic: Serialize LVTT and TSC_DEADLINE writes Kamal Mostafa <kamal@canonical.com> - 2015-10-27 22:50 +0100

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