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-rw-r--r--Documentation/kernel-parameters.txt5
-rw-r--r--arch/x86/include/asm/pkeys.h1
-rw-r--r--arch/x86/kernel/fpu/core.c4
-rw-r--r--arch/x86/mm/pkeys.c38
-rw-r--r--include/linux/pkeys.h4
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 */