This sysctl supports a value from -1 to 1 which will let the administrator decide whether or not to adjust the PTI behaviour per process.
Signed-off-by: Willy Tarreau <[email protected]> Cc: Andy Lutomirski <[email protected]> Cc: Borislav Petkov <[email protected]> Cc: Brian Gerst <[email protected]> Cc: Dave Hansen <[email protected]> Cc: Ingo Molnar <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: Josh Poimboeuf <[email protected]> Cc: "H. Peter Anvin" <[email protected]> Cc: Kees Cook <[email protected]> --- arch/x86/include/asm/pti.h | 5 +++++ arch/x86/mm/pti.c | 19 +++++++++++++++++++ kernel/sysctl.c | 12 ++++++++++++ 3 files changed, 36 insertions(+) diff --git a/arch/x86/include/asm/pti.h b/arch/x86/include/asm/pti.h index 0b5ef05..cc8e0d0e 100644 --- a/arch/x86/include/asm/pti.h +++ b/arch/x86/include/asm/pti.h @@ -6,6 +6,11 @@ #ifdef CONFIG_PAGE_TABLE_ISOLATION extern void pti_init(void); extern void pti_check_boottime_disable(void); +# ifdef CONFIG_PER_PROCESS_PTI +extern int pti_adjust; +int pti_adjust_sysctl_handler(struct ctl_table *table, int write, + void __user *buffer, size_t *lenp, loff_t *ppos); +# endif #else static inline void pti_check_boottime_disable(void) { } #endif diff --git a/arch/x86/mm/pti.c b/arch/x86/mm/pti.c index 43d4a4a..8166686f 100644 --- a/arch/x86/mm/pti.c +++ b/arch/x86/mm/pti.c @@ -54,6 +54,10 @@ #define __GFP_NOTRACK 0 #endif +# ifdef CONFIG_PER_PROCESS_PTI +int pti_adjust; +#endif + static void __init pti_print_if_insecure(const char *reason) { if (boot_cpu_has_bug(X86_BUG_CPU_MELTDOWN)) @@ -371,6 +375,21 @@ static void __init pti_clone_entry_text(void) _PAGE_RW | _PAGE_GLOBAL); } +#ifdef CONFIG_PER_PROCESS_PTI +/* + * sysctl handler for pti_adjust which decides whether or not to accept a + * change to the value. 0 and 1 may be interchanged, but -1 is definitive. + */ +int pti_adjust_sysctl_handler(struct ctl_table *table, int write, + void __user *buffer, size_t *lenp, loff_t *ppos) +{ + if (write && (!capable(CAP_SYS_RAWIO) || pti_adjust == -1)) + return -EPERM; + + return proc_dointvec_minmax(table, write, buffer, lenp, ppos); +} +#endif + /* * Initialize kernel page table isolation */ diff --git a/kernel/sysctl.c b/kernel/sysctl.c index 557d467..a37a5e1 100644 --- a/kernel/sysctl.c +++ b/kernel/sysctl.c @@ -34,6 +34,7 @@ #include <linux/fs.h> #include <linux/init.h> #include <linux/kernel.h> +#include <linux/pti.h> #include <linux/kobject.h> #include <linux/net.h> #include <linux/sysrq.h> @@ -1572,6 +1573,17 @@ static int sysrq_sysctl_handler(struct ctl_table *table, int write, .proc_handler = numa_zonelist_order_handler, }, #endif +#ifdef CONFIG_PER_PROCESS_PTI + { + .procname = "pti_adjust", + .data = &pti_adjust, + .maxlen = sizeof(int), + .mode = 0644, + .proc_handler = pti_adjust_sysctl_handler, + .extra1 = &neg_one, + .extra2 = &one, + }, +#endif #if (defined(CONFIG_X86_32) && !defined(CONFIG_UML))|| \ (defined(CONFIG_SUPERH) && defined(CONFIG_VSYSCALL)) { -- 1.7.12.1
