Patch "x86: Implement array_index_mask_nospec" has been added to the 4.4-stable tree

[<gregkh@linuxfoundation.org>]

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

    x86: Implement array_index_mask_nospec

to the 4.4-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:
     x86-implement-array_index_mask_nospec.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From foo@baz Fri Feb 23 17:23:58 CET 2018
From: Jack Wang <jinpu.wang@profitbricks.com>
Date: Fri, 23 Feb 2018 11:42:01 +0100
Subject: x86: Implement array_index_mask_nospec
To: gregkh@linuxfoundation.org, stable@vger.kernel.org
Cc: Dan Williams <dan.j.williams@intel.com>, Thomas Gleixner <tglx@linutronix.de>, linux-arch@vger.kernel.org, kernel-hardening@lists.openwall.com, alan@linux.intel.com, David Woodhouse <dwmw@amazon.co.uk>, Jack Wang <jinpu.wang@profitbricks.com>
Message-ID: <1519382538-15143-13-git-send-email-jinpu.wangl@profitbricks.com>

From: Dan Williams <dan.j.williams@intel.com>

(cherry picked from commit babdde2698d482b6c0de1eab4f697cf5856c5859)

array_index_nospec() uses a mask to sanitize user controllable array
indexes, i.e. generate a 0 mask if 'index' >= 'size', and a ~0 mask
otherwise. While the default array_index_mask_nospec() handles the
carry-bit from the (index - size) result in software.

The x86 array_index_mask_nospec() does the same, but the carry-bit is
handled in the processor CF flag without conditional instructions in the
control flow.

Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-arch@vger.kernel.org
Cc: kernel-hardening@lists.openwall.com
Cc: gregkh@linuxfoundation.org
Cc: alan@linux.intel.com
Link: https://lkml.kernel.org/r/151727414808.33451.1873237130672785331.stgit@dwillia2-desk3.amr.corp.intel.com
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
[jwang:chery pick to 4.4]
Signed-off-by: Jack Wang <jinpu.wang@profitbricks.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 arch/x86/include/asm/barrier.h |   24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

--- a/arch/x86/include/asm/barrier.h
+++ b/arch/x86/include/asm/barrier.h
@@ -24,6 +24,30 @@
 #define wmb()	asm volatile("sfence" ::: "memory")
 #endif
 
+/**
+ * array_index_mask_nospec() - generate a mask that is ~0UL when the
+ * 	bounds check succeeds and 0 otherwise
+ * @index: array element index
+ * @size: number of elements in array
+ *
+ * Returns:
+ *     0 - (index < size)
+ */
+static inline unsigned long array_index_mask_nospec(unsigned long index,
+		unsigned long size)
+{
+	unsigned long mask;
+
+	asm ("cmp %1,%2; sbb %0,%0;"
+			:"=r" (mask)
+			:"r"(size),"r" (index)
+			:"cc");
+	return mask;
+}
+
+/* Override the default implementation from linux/nospec.h. */
+#define array_index_mask_nospec array_index_mask_nospec
+
 #ifdef CONFIG_X86_PPRO_FENCE
 #define dma_rmb()	rmb()
 #else


Patches currently in stable-queue which might be from jinpu.wang@profitbricks.com are

queue-4.4/x86-paravirt-remove-noreplace-paravirt-cmdline-option.patch
queue-4.4/documentation-document-array_index_nospec.patch
queue-4.4/kvm-x86-make-indirect-calls-in-emulator-speculation-safe.patch
queue-4.4/x86-nospec-fix-header-guards-names.patch
queue-4.4/x86-retpoline-avoid-retpolines-for-built-in-__init-functions.patch
queue-4.4/vfs-fdtable-prevent-bounds-check-bypass-via-speculative-execution.patch
queue-4.4/kvm-nvmx-invvpid-handling-improvements.patch
queue-4.4/x86-cpu-bugs-make-retpoline-module-warning-conditional.patch
queue-4.4/x86-spectre-check-config_retpoline-in-command-line-parser.patch
queue-4.4/x86-implement-array_index_mask_nospec.patch
queue-4.4/array_index_nospec-sanitize-speculative-array-de-references.patch
queue-4.4/kvm-vmx-make-indirect-call-speculation-safe.patch
queue-4.4/x86-spectre-fix-spelling-mistake-vunerable-vulnerable.patch
queue-4.4/kvm-nvmx-fix-kernel-panics-induced-by-illegal-invept-invvpid-types.patch
queue-4.4/module-retpoline-warn-about-missing-retpoline-in-module.patch
queue-4.4/x86-kvm-update-spectre-v1-mitigation.patch
queue-4.4/x86-get_user-use-pointer-masking-to-limit-speculation.patch
queue-4.4/x86-syscall-sanitize-syscall-table-de-references-under-speculation.patch
queue-4.4/kvm-nvmx-vmx_complete_nested_posted_interrupt-can-t-fail.patch
queue-4.4/x86-spectre-simplify-spectre_v2-command-line-parsing.patch
queue-4.4/x86-speculation-fix-typo-ibrs_att-which-should-be-ibrs_all.patch
queue-4.4/x86-spectre-report-get_user-mitigation-for-spectre_v1.patch
queue-4.4/x86-introduce-barrier_nospec.patch
queue-4.4/kvm-async_pf-fix-df-due-to-inject-page-not-present-and-page-ready-exceptions-simultaneously.patch
queue-4.4/kvm-vmx-clean-up-declaration-of-vpid-ept-invalidation-types.patch
queue-4.4/x86-bugs-drop-one-mitigation-from-dmesg.patch
queue-4.4/x86-retpoline-remove-the-esp-rsp-thunk.patch
queue-4.4/nl80211-sanitize-array-index-in-parse_txq_params.patch
queue-4.4/kvm-nvmx-kmap-can-t-fail.patch