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From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-kernel@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	stable@vger.kernel.org, Andi Kleen <ak@linux.intel.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Josh Poimboeuf <jpoimboe@redhat.com>,
	Michal Hocko <mhocko@suse.com>,
	Dave Hansen <dave.hansen@intel.com>,
	David Woodhouse <dwmw@amazon.co.uk>,
	Guenter Roeck <linux@roeck-us.net>
Subject: [PATCH 4.4 21/43] x86/speculation/l1tf: Increase 32bit PAE __PHYSICAL_PAGE_SHIFT
Date: Tue, 14 Aug 2018 19:17:57 +0200	[thread overview]
Message-ID: <20180814171518.521157143@linuxfoundation.org> (raw)
In-Reply-To: <20180814171517.014285600@linuxfoundation.org>

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

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

From: Andi Kleen <ak@linux.intel.com>

commit 50896e180c6aa3a9c61a26ced99e15d602666a4c upstream

L1 Terminal Fault (L1TF) is a speculation related vulnerability. The CPU
speculates on PTE entries which do not have the PRESENT bit set, if the
content of the resulting physical address is available in the L1D cache.

The OS side mitigation makes sure that a !PRESENT PTE entry points to a
physical address outside the actually existing and cachable memory
space. This is achieved by inverting the upper bits of the PTE. Due to the
address space limitations this only works for 64bit and 32bit PAE kernels,
but not for 32bit non PAE.

This mitigation applies to both host and guest kernels, but in case of a
64bit host (hypervisor) and a 32bit PAE guest, inverting the upper bits of
the PAE address space (44bit) is not enough if the host has more than 43
bits of populated memory address space, because the speculation treats the
PTE content as a physical host address bypassing EPT.

The host (hypervisor) protects itself against the guest by flushing L1D as
needed, but pages inside the guest are not protected against attacks from
other processes inside the same guest.

For the guest the inverted PTE mask has to match the host to provide the
full protection for all pages the host could possibly map into the
guest. The hosts populated address space is not known to the guest, so the
mask must cover the possible maximal host address space, i.e. 52 bit.

On 32bit PAE the maximum PTE mask is currently set to 44 bit because that
is the limit imposed by 32bit unsigned long PFNs in the VMs. This limits
the mask to be below what the host could possible use for physical pages.

The L1TF PROT_NONE protection code uses the PTE masks to determine which
bits to invert to make sure the higher bits are set for unmapped entries to
prevent L1TF speculation attacks against EPT inside guests.

In order to invert all bits that could be used by the host, increase
__PHYSICAL_PAGE_SHIFT to 52 to match 64bit.

The real limit for a 32bit PAE kernel is still 44 bits because all Linux
PTEs are created from unsigned long PFNs, so they cannot be higher than 44
bits on a 32bit kernel. So these extra PFN bits should be never set. The
only users of this macro are using it to look at PTEs, so it's safe.

[ tglx: Massaged changelog ]

Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Dave Hansen <dave.hansen@intel.com>
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 arch/x86/include/asm/page_32_types.h |    9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

--- a/arch/x86/include/asm/page_32_types.h
+++ b/arch/x86/include/asm/page_32_types.h
@@ -27,8 +27,13 @@
 #define N_EXCEPTION_STACKS 1
 
 #ifdef CONFIG_X86_PAE
-/* 44=32+12, the limit we can fit into an unsigned long pfn */
-#define __PHYSICAL_MASK_SHIFT	44
+/*
+ * This is beyond the 44 bit limit imposed by the 32bit long pfns,
+ * but we need the full mask to make sure inverted PROT_NONE
+ * entries have all the host bits set in a guest.
+ * The real limit is still 44 bits.
+ */
+#define __PHYSICAL_MASK_SHIFT	52
 #define __VIRTUAL_MASK_SHIFT	32
 
 #else  /* !CONFIG_X86_PAE */



  parent reply	other threads:[~2018-08-14 17:46 UTC|newest]

Thread overview: 51+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-08-14 17:17 [PATCH 4.4 00/43] 4.4.148-stable review Greg Kroah-Hartman
2018-08-14 17:17 ` [PATCH 4.4 01/43] ext4: fix check to prevent initializing reserved inodes Greg Kroah-Hartman
2018-08-14 17:17 ` [PATCH 4.4 02/43] tpm: fix race condition in tpm_common_write() Greg Kroah-Hartman
2018-08-14 17:17 ` [PATCH 4.4 03/43] ipv4+ipv6: Make INET*_ESP select CRYPTO_ECHAINIV Greg Kroah-Hartman
2018-08-14 17:17 ` [PATCH 4.4 04/43] fork: unconditionally clear stack on fork Greg Kroah-Hartman
2018-08-14 17:17 ` [PATCH 4.4 05/43] parisc: Enable CONFIG_MLONGCALLS by default Greg Kroah-Hartman
2018-08-14 17:17 ` [PATCH 4.4 07/43] xen/netfront: dont cache skb_shinfo() Greg Kroah-Hartman
2018-08-14 17:17 ` [PATCH 4.4 08/43] ACPI / LPSS: Add missing prv_offset setting for byt/cht PWM devices Greg Kroah-Hartman
2018-08-14 17:17 ` [PATCH 4.4 09/43] scsi: sr: Avoid that opening a CD-ROM hangs with runtime power management enabled Greg Kroah-Hartman
2018-08-14 17:17 ` [PATCH 4.4 10/43] root dentries need RCU-delayed freeing Greg Kroah-Hartman
2018-08-14 17:17 ` [PATCH 4.4 11/43] fix mntput/mntput race Greg Kroah-Hartman
2018-08-14 17:17 ` [PATCH 4.4 12/43] fix __legitimize_mnt()/mntput() race Greg Kroah-Hartman
2018-08-14 17:17 ` [PATCH 4.4 13/43] IB/core: Make testing MR flags for writability a static inline function Greg Kroah-Hartman
2018-08-14 17:17 ` [PATCH 4.4 14/43] IB/mlx4: Mark user MR as writable if actual virtual memory is writable Greg Kroah-Hartman
2018-08-14 17:17 ` [PATCH 4.4 15/43] IB/ocrdma: fix out of bounds access to local buffer Greg Kroah-Hartman
2018-08-14 17:17 ` [PATCH 4.4 16/43] ARM: dts: imx6sx: fix irq for pcie bridge Greg Kroah-Hartman
2018-08-14 17:17 ` [PATCH 4.4 17/43] x86/paravirt: Fix spectre-v2 mitigations for paravirt guests Greg Kroah-Hartman
2018-08-14 17:17 ` [PATCH 4.4 18/43] x86/speculation: Protect against userspace-userspace spectreRSB Greg Kroah-Hartman
2018-08-14 17:17 ` [PATCH 4.4 19/43] kprobes/x86: Fix %p uses in error messages Greg Kroah-Hartman
2018-08-14 17:17 ` [PATCH 4.4 20/43] x86/irqflags: Provide a declaration for native_save_fl Greg Kroah-Hartman
2018-08-14 17:17 ` Greg Kroah-Hartman [this message]
2018-08-14 17:17 ` [PATCH 4.4 22/43] x86/mm: Move swap offset/type up in PTE to work around erratum Greg Kroah-Hartman
2018-08-14 17:17 ` [PATCH 4.4 23/43] x86/mm: Fix swap entry comment and macro Greg Kroah-Hartman
2018-08-14 17:18 ` [PATCH 4.4 24/43] mm: x86: move _PAGE_SWP_SOFT_DIRTY from bit 7 to bit 1 Greg Kroah-Hartman
2018-08-14 17:18 ` [PATCH 4.4 25/43] x86/speculation/l1tf: Change order of offset/type in swap entry Greg Kroah-Hartman
2018-08-14 17:18 ` [PATCH 4.4 26/43] x86/speculation/l1tf: Protect swap entries against L1TF Greg Kroah-Hartman
2018-08-14 17:18 ` [PATCH 4.4 27/43] x86/speculation/l1tf: Protect PROT_NONE PTEs against speculation Greg Kroah-Hartman
2018-08-14 17:18 ` [PATCH 4.4 28/43] x86/speculation/l1tf: Make sure the first page is always reserved Greg Kroah-Hartman
2018-08-14 17:18 ` [PATCH 4.4 29/43] x86/speculation/l1tf: Add sysfs reporting for l1tf Greg Kroah-Hartman
2018-08-14 17:18 ` [PATCH 4.4 30/43] mm: Add vm_insert_pfn_prot() Greg Kroah-Hartman
2018-08-14 17:18 ` [PATCH 4.4 31/43] mm: fix cache mode tracking in vm_insert_mixed() Greg Kroah-Hartman
2018-09-07 17:05   ` Ben Hutchings
2018-09-07 20:03     ` Greg Kroah-Hartman
2018-08-14 17:18 ` [PATCH 4.4 32/43] x86/speculation/l1tf: Disallow non privileged high MMIO PROT_NONE mappings Greg Kroah-Hartman
2018-08-14 17:18 ` [PATCH 4.4 33/43] x86/speculation/l1tf: Limit swap file size to MAX_PA/2 Greg Kroah-Hartman
2018-08-14 17:18 ` [PATCH 4.4 34/43] x86/bugs: Move the l1tf function and define pr_fmt properly Greg Kroah-Hartman
2018-08-14 17:18 ` [PATCH 4.4 35/43] x86/speculation/l1tf: Extend 64bit swap file size limit Greg Kroah-Hartman
2018-08-14 17:18 ` [PATCH 4.4 36/43] x86/cpufeatures: Add detection of L1D cache flush support Greg Kroah-Hartman
2018-08-14 17:18 ` [PATCH 4.4 37/43] x86/speculation/l1tf: Protect PAE swap entries against L1TF Greg Kroah-Hartman
2018-08-14 17:18 ` [PATCH 4.4 38/43] x86/speculation/l1tf: Fix up pte->pfn conversion for PAE Greg Kroah-Hartman
2018-08-14 17:18 ` [PATCH 4.4 39/43] x86/speculation/l1tf: Invert all not present mappings Greg Kroah-Hartman
2018-08-14 17:18 ` [PATCH 4.4 40/43] x86/speculation/l1tf: Make pmd/pud_mknotpresent() invert Greg Kroah-Hartman
2018-08-14 17:18 ` [PATCH 4.4 41/43] x86/mm/pat: Make set_memory_np() L1TF safe Greg Kroah-Hartman
2018-09-09 16:46   ` Ben Hutchings
2018-09-09 17:06     ` Guenter Roeck
2018-09-10  7:16       ` Greg Kroah-Hartman
2018-08-14 17:18 ` [PATCH 4.4 42/43] x86/mm/kmmio: Make the tracer robust against L1TF Greg Kroah-Hartman
2018-08-14 17:18 ` [PATCH 4.4 43/43] x86/speculation/l1tf: Fix up CPU feature flags Greg Kroah-Hartman
2018-08-15  6:15 ` [PATCH 4.4 00/43] 4.4.148-stable review Greg Kroah-Hartman
2018-08-15 13:10 ` Guenter Roeck
2018-08-15 20:52 ` Dan Rue

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