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

x86/kaiser: Check boottime cmdline params

to the 4.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: x86-kaiser-check-boottime-cmdline-params.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 Wed Jan 3 18:58:12 CET 2018

From: Borislav Petkov bp@suse.de Date: Tue, 2 Jan 2018 14:19:48 +0100 Subject: x86/kaiser: Check boottime cmdline params

From: Borislav Petkov bp@suse.de

AMD (and possibly other vendors) are not affected by the leak KAISER is protecting against.

Keep the "nopti" for traditional reasons and add pti=<on|off|auto> like upstream.

Signed-off-by: Borislav Petkov bp@suse.de Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- Documentation/kernel-parameters.txt | 6 +++ arch/x86/mm/kaiser.c | 59 +++++++++++++++++++++++++----------- 2 files changed, 47 insertions(+), 18 deletions(-)

--- a/Documentation/kernel-parameters.txt +++ b/Documentation/kernel-parameters.txt @@ -3056,6 +3056,12 @@ bytes respectively. Such letter suffixes pt. [PARIDE] See Documentation/blockdev/paride.txt.

+ pti= [X86_64] + Control KAISER user/kernel address space isolation: + on - enable + off - disable + auto - default setting + pty.legacy_count= [KNL] Number of legacy pty's. Overwrites compiled-in default number. --- a/arch/x86/mm/kaiser.c +++ b/arch/x86/mm/kaiser.c @@ -16,6 +16,7 @@ #include <asm/pgtable.h> #include <asm/pgalloc.h> #include <asm/desc.h> +#include <asm/cmdline.h>

int kaiser_enabled __read_mostly = 1; EXPORT_SYMBOL(kaiser_enabled); /* for inlined TLB flush functions */ @@ -264,6 +265,43 @@ static void __init kaiser_init_all_pgds( WARN_ON(__ret); \ } while (0)

+void __init kaiser_check_boottime_disable(void) +{ + bool enable = true; + char arg[5]; + int ret; + + ret = cmdline_find_option(boot_command_line, "pti", arg, sizeof(arg)); + if (ret > 0) { + if (!strncmp(arg, "on", 2)) + goto enable; + + if (!strncmp(arg, "off", 3)) + goto disable; + + if (!strncmp(arg, "auto", 4)) + goto skip; + } + + if (cmdline_find_option_bool(boot_command_line, "nopti")) + goto disable; + +skip: + if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD) + goto disable; + +enable: + if (enable) + setup_force_cpu_cap(X86_FEATURE_KAISER); + + return; + +disable: + pr_info("Kernel/User page tables isolation: disabled\n"); + kaiser_enabled = 0; + setup_clear_cpu_cap(X86_FEATURE_KAISER); +} + /* * If anything in here fails, we will likely die on one of the * first kernel->user transitions and init will die. But, we @@ -275,12 +313,10 @@ void __init kaiser_init(void) { int cpu;

- if (!kaiser_enabled) { - setup_clear_cpu_cap(X86_FEATURE_KAISER); - return; - } + kaiser_check_boottime_disable();

- setup_force_cpu_cap(X86_FEATURE_KAISER); + if (!kaiser_enabled) + return;

kaiser_init_all_pgds();

@@ -424,16 +460,3 @@ void kaiser_flush_tlb_on_return_to_user( X86_CR3_PCID_USER_FLUSH | KAISER_SHADOW_PGD_OFFSET); } EXPORT_SYMBOL(kaiser_flush_tlb_on_return_to_user); - -static int __init x86_nokaiser_setup(char *s) -{ - /* nopti doesn't accept parameters */ - if (s) - return -EINVAL; - - kaiser_enabled = 0; - pr_info("Kernel/User page tables isolation: disabled\n"); - - return 0; -} -early_param("nopti", x86_nokaiser_setup);

Patches currently in stable-queue which might be from bp@suse.de are

queue-4.4/x86-paravirt-dont-patch-flush_tlb_single.patch queue-4.4/x86-kaiser-reenable-paravirt.patch queue-4.4/x86-kaiser-rename-and-simplify-x86_feature_kaiser-handling.patch queue-4.4/x86-kaiser-check-boottime-cmdline-params.patch queue-4.4/x86-kaiser-move-feature-detection-up.patch