From cbbe8c229211a56d12058b930bf8a25201be2f23 Mon Sep 17 00:00:00 2001 From: Michael Ellerman Date: Wed, 10 Jan 2018 23:36:43 +0530 Subject: [PATCH 11/26] UBUNTU: SAUCE: rfi-flush: Move the logic to avoid a redo into the sysfs code CVE-2017-5754 rfi_flush_enable() includes a check to see if we're already enabled (or disabled), and in that case does nothing. But that means calling setup_rfi_flush() a 2nd time doesn't actually work, which is a bit confusing. Move that check into the sysfs code, where it really belongs. Signed-off-by: Michael Ellerman Signed-off-by: Stefan Bader --- arch/powerpc/kernel/setup_64.c | 3 --- arch/powerpc/kernel/sysfs.c | 9 +++++++-- 2 files changed, 7 insertions(+), 5 deletions(-) diff --git a/arch/powerpc/kernel/setup_64.c b/arch/powerpc/kernel/setup_64.c index fce5831..f52190f 100644 --- a/arch/powerpc/kernel/setup_64.c +++ b/arch/powerpc/kernel/setup_64.c @@ -763,9 +763,6 @@ static void do_nothing(void *unused) void rfi_flush_enable(bool enable) { - if (rfi_flush == enable) - return; - if (enable) { do_rfi_flush_fixups(enabled_flush_types); on_each_cpu(do_nothing, NULL, 1); diff --git a/arch/powerpc/kernel/sysfs.c b/arch/powerpc/kernel/sysfs.c index 66025932..2832afd 100644 --- a/arch/powerpc/kernel/sysfs.c +++ b/arch/powerpc/kernel/sysfs.c @@ -194,6 +194,7 @@ static ssize_t __used store_rfi_flush(struct device *dev, struct device_attribute *attr, const char *buf, size_t count) { + bool enable; int val; int ret = 0; @@ -202,12 +203,16 @@ static ssize_t __used store_rfi_flush(struct device *dev, return -EINVAL; if (val == 1) - rfi_flush_enable(true); + enable = true; else if (val == 0) - rfi_flush_enable(false); + enable = false; else return -EINVAL; + /* Only do anything if we're changing state */ + if (enable != rfi_flush) + rfi_flush_enable(enable); + return count; } -- 2.7.4