diff options
| -rw-r--r-- | Documentation/kernel-parameters.txt | 5 | ||||
| -rw-r--r-- | arch/x86/include/asm/pkeys.h | 1 | ||||
| -rw-r--r-- | arch/x86/kernel/fpu/core.c | 4 | ||||
| -rw-r--r-- | arch/x86/mm/pkeys.c | 38 | ||||
| -rw-r--r-- | include/linux/pkeys.h | 4 |
5 files changed, 52 insertions, 0 deletions
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt index a4f4d693e2c1..3725976d0af5 100644 --- a/Documentation/kernel-parameters.txt +++ b/Documentation/kernel-parameters.txt @@ -1643,6 +1643,11 @@ bytes respectively. Such letter suffixes can also be entirely omitted. initrd= [BOOT] Specify the location of the initial ramdisk + init_pkru= [x86] Specify the default memory protection keys rights + register contents for all processes. 0x55555554 by + default (disallow access to all but pkey 0). Can + override in debugfs after boot. + inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver Format: <irq> diff --git a/arch/x86/include/asm/pkeys.h b/arch/x86/include/asm/pkeys.h index b406889de0db..34684adb6899 100644 --- a/arch/x86/include/asm/pkeys.h +++ b/arch/x86/include/asm/pkeys.h @@ -100,5 +100,6 @@ extern int arch_set_user_pkey_access(struct task_struct *tsk, int pkey, unsigned long init_val); extern int __arch_set_user_pkey_access(struct task_struct *tsk, int pkey, unsigned long init_val); +extern void copy_init_pkru_to_fpregs(void); #endif /*_ASM_X86_PKEYS_H */ diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c index 3fc03a09a93b..47004010ad5d 100644 --- a/arch/x86/kernel/fpu/core.c +++ b/arch/x86/kernel/fpu/core.c @@ -12,6 +12,7 @@ #include <asm/traps.h> #include <linux/hardirq.h> +#include <linux/pkeys.h> #define CREATE_TRACE_POINTS #include <asm/trace/fpu.h> @@ -505,6 +506,9 @@ static inline void copy_init_fpstate_to_fpregs(void) copy_kernel_to_fxregs(&init_fpstate.fxsave); else copy_kernel_to_fregs(&init_fpstate.fsave); + + if (boot_cpu_has(X86_FEATURE_OSPKE)) + copy_init_pkru_to_fpregs(); } /* diff --git a/arch/x86/mm/pkeys.c b/arch/x86/mm/pkeys.c index e6113bbb56e1..ddc54949078a 100644 --- a/arch/x86/mm/pkeys.c +++ b/arch/x86/mm/pkeys.c @@ -121,3 +121,41 @@ int __arch_override_mprotect_pkey(struct vm_area_struct *vma, int prot, int pkey */ return vma_pkey(vma); } + +#define PKRU_AD_KEY(pkey) (PKRU_AD_BIT << ((pkey) * PKRU_BITS_PER_PKEY)) + +/* + * Make the default PKRU value (at execve() time) as restrictive + * as possible. This ensures that any threads clone()'d early + * in the process's lifetime will not accidentally get access + * to data which is pkey-protected later on. + */ +u32 init_pkru_value = PKRU_AD_KEY( 1) | PKRU_AD_KEY( 2) | PKRU_AD_KEY( 3) | + PKRU_AD_KEY( 4) | PKRU_AD_KEY( 5) | PKRU_AD_KEY( 6) | + PKRU_AD_KEY( 7) | PKRU_AD_KEY( 8) | PKRU_AD_KEY( 9) | + PKRU_AD_KEY(10) | PKRU_AD_KEY(11) | PKRU_AD_KEY(12) | + PKRU_AD_KEY(13) | PKRU_AD_KEY(14) | PKRU_AD_KEY(15); + +/* + * Called from the FPU code when creating a fresh set of FPU + * registers. This is called from a very specific context where + * we know the FPU regstiers are safe for use and we can use PKRU + * directly. The fact that PKRU is only available when we are + * using eagerfpu mode makes this possible. + */ +void copy_init_pkru_to_fpregs(void) +{ + u32 init_pkru_value_snapshot = READ_ONCE(init_pkru_value); + /* + * Any write to PKRU takes it out of the XSAVE 'init + * state' which increases context switch cost. Avoid + * writing 0 when PKRU was already 0. + */ + if (!init_pkru_value_snapshot && !read_pkru()) + return; + /* + * Override the PKRU state that came from 'init_fpstate' + * with the baseline from the process. + */ + write_pkru(init_pkru_value_snapshot); +} diff --git a/include/linux/pkeys.h b/include/linux/pkeys.h index 8ff21125dc8a..e4c08c1ff0c5 100644 --- a/include/linux/pkeys.h +++ b/include/linux/pkeys.h @@ -35,6 +35,10 @@ static inline int arch_set_user_pkey_access(struct task_struct *tsk, int pkey, return 0; } +static inline void copy_init_pkru_to_fpregs(void) +{ +} + #endif /* ! CONFIG_ARCH_HAS_PKEYS */ #endif /* _LINUX_PKEYS_H */ |