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Commit ba830885 authored by Kristina Martsenko's avatar Kristina Martsenko Committed by Will Deacon
Browse files

arm64: add prctl control for resetting ptrauth keys 



Add an arm64-specific prctl to allow a thread to reinitialize its
pointer authentication keys to random values. This can be useful when
exec() is not used for starting new processes, to ensure that different
processes still have different keys.

Signed-off-by: default avatarKristina Martsenko <kristina.martsenko@arm.com>
Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
parent ccc43810

arch/arm64/include/asm/pointer_auth.h

+3 −0
Original line number Diff line number Diff line
@@ -63,6 +63,8 @@ static inline void ptrauth_keys_switch(struct ptrauth_keys *keys) 
		__ptrauth_key_install(APGA, keys->apga);

}



extern int ptrauth_prctl_reset_keys(struct task_struct *tsk, unsigned long arg);



/*

 * The EL0 pointer bits used by a pointer authentication code.

 * This is dependent on TBI0 being enabled, or bits 63:56 would also apply.
@@ -86,6 +88,7 @@ do { \ 
	ptrauth_keys_switch(&(tsk)->thread_info.keys_user)



#else /* CONFIG_ARM64_PTR_AUTH */

#define ptrauth_prctl_reset_keys(tsk, arg)	(-EINVAL)

#define ptrauth_strip_insn_pac(lr)	(lr)

#define ptrauth_thread_init_user(tsk)

#define ptrauth_thread_switch(tsk)

arch/arm64/include/asm/processor.h

+4 −0
Original line number Diff line number Diff line
@@ -44,6 +44,7 @@ 
#include <asm/hw_breakpoint.h>

#include <asm/lse.h>

#include <asm/pgtable-hwdef.h>

#include <asm/pointer_auth.h>

#include <asm/ptrace.h>

#include <asm/types.h>
@@ -289,6 +290,9 @@ extern void __init minsigstksz_setup(void); 
#define SVE_SET_VL(arg)	sve_set_current_vl(arg)

#define SVE_GET_VL()	sve_get_current_vl()



/* PR_PAC_RESET_KEYS prctl */

#define PAC_RESET_KEYS(tsk, arg)	ptrauth_prctl_reset_keys(tsk, arg)



/*

 * For CONFIG_GCC_PLUGIN_STACKLEAK

 *

arch/arm64/kernel/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -58,6 +58,7 @@ arm64-obj-$(CONFIG_CRASH_DUMP) += crash_dump.o 
arm64-obj-$(CONFIG_CRASH_CORE)		+= crash_core.o

arm64-obj-$(CONFIG_ARM_SDE_INTERFACE)	+= sdei.o

arm64-obj-$(CONFIG_ARM64_SSBD)		+= ssbd.o

arm64-obj-$(CONFIG_ARM64_PTR_AUTH)	+= pointer_auth.o



obj-y					+= $(arm64-obj-y) vdso/ probes/

obj-m					+= $(arm64-obj-m)

arch/arm64/kernel/pointer_auth.c

0 → 100644
+47 −0
Original line number Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0



#include <linux/errno.h>

#include <linux/prctl.h>

#include <linux/random.h>

#include <linux/sched.h>

#include <asm/cpufeature.h>

#include <asm/pointer_auth.h>



int ptrauth_prctl_reset_keys(struct task_struct *tsk, unsigned long arg)

{

	struct ptrauth_keys *keys = &tsk->thread_info.keys_user;

	unsigned long addr_key_mask = PR_PAC_APIAKEY | PR_PAC_APIBKEY |

				      PR_PAC_APDAKEY | PR_PAC_APDBKEY;

	unsigned long key_mask = addr_key_mask | PR_PAC_APGAKEY;



	if (!system_supports_address_auth() && !system_supports_generic_auth())

		return -EINVAL;



	if (!arg) {

		ptrauth_keys_init(keys);

		ptrauth_keys_switch(keys);

		return 0;

	}



	if (arg & ~key_mask)

		return -EINVAL;



	if (((arg & addr_key_mask) && !system_supports_address_auth()) ||

	    ((arg & PR_PAC_APGAKEY) && !system_supports_generic_auth()))

		return -EINVAL;



	if (arg & PR_PAC_APIAKEY)

		get_random_bytes(&keys->apia, sizeof(keys->apia));

	if (arg & PR_PAC_APIBKEY)

		get_random_bytes(&keys->apib, sizeof(keys->apib));

	if (arg & PR_PAC_APDAKEY)

		get_random_bytes(&keys->apda, sizeof(keys->apda));

	if (arg & PR_PAC_APDBKEY)

		get_random_bytes(&keys->apdb, sizeof(keys->apdb));

	if (arg & PR_PAC_APGAKEY)

		get_random_bytes(&keys->apga, sizeof(keys->apga));



	ptrauth_keys_switch(keys);



	return 0;

}

include/uapi/linux/prctl.h

+8 −0
Original line number Diff line number Diff line
@@ -219,4 +219,12 @@ struct prctl_mm_map { 
# define PR_SPEC_DISABLE		(1UL << 2)

# define PR_SPEC_FORCE_DISABLE		(1UL << 3)



/* Reset arm64 pointer authentication keys */

#define PR_PAC_RESET_KEYS		54

# define PR_PAC_APIAKEY			(1UL << 0)

# define PR_PAC_APIBKEY			(1UL << 1)

# define PR_PAC_APDAKEY			(1UL << 2)

# define PR_PAC_APDBKEY			(1UL << 3)

# define PR_PAC_APGAKEY			(1UL << 4)



#endif /* _LINUX_PRCTL_H */