Subject: Re: [PATCH 06/11] arm64: rename ptrauth key structures to be user-specific

From: Kees Cook <[email-masked]>
Date: Tue, 29 Oct 2019 16:27:51 -0700

On Thu, Oct 17, 2019 at 01:44:20PM +0530, Amit Daniel Kachhap wrote:
> From: Kristina Martsenko <[email-masked]>
> 
> We currently enable ptrauth for userspace, but do not use it within the
> kernel. We're going to enable it for the kernel, and will need to manage
> a separate set of ptrauth keys for the kernel.
> 
> We currently keep all 5 keys in struct ptrauth_keys. However, as the
> kernel will only need to use 1 key, it is a bit wasteful to allocate a
> whole ptrauth_keys struct for every thread.
> 
> Therefore, a subsequent patch will define a separate struct, with only 1
> key, for the kernel. In preparation for that, rename the existing struct
> (and associated macros and functions) to reflect that they are specific
> to userspace.
> 
> Signed-off-by: Kristina Martsenko <[email-masked]>

This appears very mechanical; easy to review! ;)

Reviewed-by: Kees Cook <[email-masked]>

-Kees

> Signed-off-by: Amit Daniel Kachhap <[email-masked]>
> ---
> Changes since RFC v2:
>  - New patch in this version, to optimize struct usage [Dave]
> 
>  arch/arm64/include/asm/asm_pointer_auth.h | 10 +++++-----
>  arch/arm64/include/asm/pointer_auth.h     |  6 +++---
>  arch/arm64/include/asm/processor.h        |  2 +-
>  arch/arm64/kernel/asm-offsets.c           | 10 +++++-----
>  arch/arm64/kernel/pointer_auth.c          |  4 ++--
>  arch/arm64/kernel/ptrace.c                | 16 ++++++++--------
>  6 files changed, 24 insertions(+), 24 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/asm_pointer_auth.h b/arch/arm64/include/asm/asm_pointer_auth.h
> index cb21a06..3d39788 100644
> --- a/arch/arm64/include/asm/asm_pointer_auth.h
> +++ b/arch/arm64/include/asm/asm_pointer_auth.h
> @@ -15,21 +15,21 @@
>  alternative_if_not ARM64_HAS_ADDRESS_AUTH
>  	b	.Laddr_auth_skip_\@
>  alternative_else_nop_endif
> -	ldp	\tmp2, \tmp3, [\tmp1, #PTRAUTH_KEY_APIA]
> +	ldp	\tmp2, \tmp3, [\tmp1, #PTRAUTH_USER_KEY_APIA]
>  	msr_s	SYS_APIAKEYLO_EL1, \tmp2
>  	msr_s	SYS_APIAKEYHI_EL1, \tmp3
> -	ldp	\tmp2, \tmp3, [\tmp1, #PTRAUTH_KEY_APIB]
> +	ldp	\tmp2, \tmp3, [\tmp1, #PTRAUTH_USER_KEY_APIB]
>  	msr_s	SYS_APIBKEYLO_EL1, \tmp2
>  	msr_s	SYS_APIBKEYHI_EL1, \tmp3
> -	ldp	\tmp2, \tmp3, [\tmp1, #PTRAUTH_KEY_APDA]
> +	ldp	\tmp2, \tmp3, [\tmp1, #PTRAUTH_USER_KEY_APDA]
>  	msr_s	SYS_APDAKEYLO_EL1, \tmp2
>  	msr_s	SYS_APDAKEYHI_EL1, \tmp3
> -	ldp	\tmp2, \tmp3, [\tmp1, #PTRAUTH_KEY_APDB]
> +	ldp	\tmp2, \tmp3, [\tmp1, #PTRAUTH_USER_KEY_APDB]
>  	msr_s	SYS_APDBKEYLO_EL1, \tmp2
>  	msr_s	SYS_APDBKEYHI_EL1, \tmp3
>  .Laddr_auth_skip_\@:
>  alternative_if ARM64_HAS_GENERIC_AUTH
> -	ldp	\tmp2, \tmp3, [\tmp1, #PTRAUTH_KEY_APGA]
> +	ldp	\tmp2, \tmp3, [\tmp1, #PTRAUTH_USER_KEY_APGA]
>  	msr_s	SYS_APGAKEYLO_EL1, \tmp2
>  	msr_s	SYS_APGAKEYHI_EL1, \tmp3
>  alternative_else_nop_endif
> diff --git a/arch/arm64/include/asm/pointer_auth.h b/arch/arm64/include/asm/pointer_auth.h
> index 21c2115..cc42145 100644
> --- a/arch/arm64/include/asm/pointer_auth.h
> +++ b/arch/arm64/include/asm/pointer_auth.h
> @@ -22,7 +22,7 @@ struct ptrauth_key {
>   * We give each process its own keys, which are shared by all threads. The keys
>   * are inherited upon fork(), and reinitialised upon exec*().
>   */
> -struct ptrauth_keys {
> +struct ptrauth_keys_user {
>  	struct ptrauth_key apia;
>  	struct ptrauth_key apib;
>  	struct ptrauth_key apda;
> @@ -30,7 +30,7 @@ struct ptrauth_keys {
>  	struct ptrauth_key apga;
>  };
>  
> -static inline void ptrauth_keys_init(struct ptrauth_keys *keys)
> +static inline void ptrauth_keys_init_user(struct ptrauth_keys_user *keys)
>  {
>  	if (system_supports_address_auth()) {
>  		get_random_bytes(&keys->apia, sizeof(keys->apia));
> @@ -58,7 +58,7 @@ static inline unsigned long ptrauth_strip_insn_pac(unsigned long ptr)
>  }
>  
>  #define ptrauth_thread_init_user(tsk)					\
> -	ptrauth_keys_init(&(tsk)->thread.keys_user)
> +	ptrauth_keys_init_user(&(tsk)->thread.keys_user)
>  
>  #else /* CONFIG_ARM64_PTR_AUTH */
>  #define ptrauth_prctl_reset_keys(tsk, arg)	(-EINVAL)
> diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/processor.h
> index 5623685..8ec792d 100644
> --- a/arch/arm64/include/asm/processor.h
> +++ b/arch/arm64/include/asm/processor.h
> @@ -144,7 +144,7 @@ struct thread_struct {
>  	unsigned long		fault_code;	/* ESR_EL1 value */
>  	struct debug_info	debug;		/* debugging */
>  #ifdef CONFIG_ARM64_PTR_AUTH
> -	struct ptrauth_keys	keys_user;
> +	struct ptrauth_keys_user	keys_user;
>  #endif
>  };
>  
> diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c
> index ef0c24b..cf15182 100644
> --- a/arch/arm64/kernel/asm-offsets.c
> +++ b/arch/arm64/kernel/asm-offsets.c
> @@ -131,11 +131,11 @@ int main(void)
>    DEFINE(SDEI_EVENT_PRIORITY,	offsetof(struct sdei_registered_event, priority));
>  #endif
>  #ifdef CONFIG_ARM64_PTR_AUTH
> -  DEFINE(PTRAUTH_KEY_APIA,	offsetof(struct ptrauth_keys, apia));
> -  DEFINE(PTRAUTH_KEY_APIB,	offsetof(struct ptrauth_keys, apib));
> -  DEFINE(PTRAUTH_KEY_APDA,	offsetof(struct ptrauth_keys, apda));
> -  DEFINE(PTRAUTH_KEY_APDB,	offsetof(struct ptrauth_keys, apdb));
> -  DEFINE(PTRAUTH_KEY_APGA,	offsetof(struct ptrauth_keys, apga));
> +  DEFINE(PTRAUTH_USER_KEY_APIA,		offsetof(struct ptrauth_keys_user, apia));
> +  DEFINE(PTRAUTH_USER_KEY_APIB,		offsetof(struct ptrauth_keys_user, apib));
> +  DEFINE(PTRAUTH_USER_KEY_APDA,		offsetof(struct ptrauth_keys_user, apda));
> +  DEFINE(PTRAUTH_USER_KEY_APDB,		offsetof(struct ptrauth_keys_user, apdb));
> +  DEFINE(PTRAUTH_USER_KEY_APGA,		offsetof(struct ptrauth_keys_user, apga));
>    BLANK();
>  #endif
>    return 0;
> diff --git a/arch/arm64/kernel/pointer_auth.c b/arch/arm64/kernel/pointer_auth.c
> index 95985be..1e77736 100644
> --- a/arch/arm64/kernel/pointer_auth.c
> +++ b/arch/arm64/kernel/pointer_auth.c
> @@ -9,7 +9,7 @@
>  
>  int ptrauth_prctl_reset_keys(struct task_struct *tsk, unsigned long arg)
>  {
> -	struct ptrauth_keys *keys = &tsk->thread.keys_user;
> +	struct ptrauth_keys_user *keys = &tsk->thread.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;
> @@ -18,7 +18,7 @@ int ptrauth_prctl_reset_keys(struct task_struct *tsk, unsigned long arg)
>  		return -EINVAL;
>  
>  	if (!arg) {
> -		ptrauth_keys_init(keys);
> +		ptrauth_keys_init_user(keys);
>  		return 0;
>  	}
>  
> diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
> index 21176d0..0793739 100644
> --- a/arch/arm64/kernel/ptrace.c
> +++ b/arch/arm64/kernel/ptrace.c
> @@ -986,7 +986,7 @@ static struct ptrauth_key pac_key_from_user(__uint128_t ukey)
>  }
>  
>  static void pac_address_keys_to_user(struct user_pac_address_keys *ukeys,
> -				     const struct ptrauth_keys *keys)
> +				     const struct ptrauth_keys_user *keys)
>  {
>  	ukeys->apiakey = pac_key_to_user(&keys->apia);
>  	ukeys->apibkey = pac_key_to_user(&keys->apib);
> @@ -994,7 +994,7 @@ static void pac_address_keys_to_user(struct user_pac_address_keys *ukeys,
>  	ukeys->apdbkey = pac_key_to_user(&keys->apdb);
>  }
>  
> -static void pac_address_keys_from_user(struct ptrauth_keys *keys,
> +static void pac_address_keys_from_user(struct ptrauth_keys_user *keys,
>  				       const struct user_pac_address_keys *ukeys)
>  {
>  	keys->apia = pac_key_from_user(ukeys->apiakey);
> @@ -1008,7 +1008,7 @@ static int pac_address_keys_get(struct task_struct *target,
>  				unsigned int pos, unsigned int count,
>  				void *kbuf, void __user *ubuf)
>  {
> -	struct ptrauth_keys *keys = &target->thread.keys_user;
> +	struct ptrauth_keys_user *keys = &target->thread.keys_user;
>  	struct user_pac_address_keys user_keys;
>  
>  	if (!system_supports_address_auth())
> @@ -1025,7 +1025,7 @@ static int pac_address_keys_set(struct task_struct *target,
>  				unsigned int pos, unsigned int count,
>  				const void *kbuf, const void __user *ubuf)
>  {
> -	struct ptrauth_keys *keys = &target->thread.keys_user;
> +	struct ptrauth_keys_user *keys = &target->thread.keys_user;
>  	struct user_pac_address_keys user_keys;
>  	int ret;
>  
> @@ -1043,12 +1043,12 @@ static int pac_address_keys_set(struct task_struct *target,
>  }
>  
>  static void pac_generic_keys_to_user(struct user_pac_generic_keys *ukeys,
> -				     const struct ptrauth_keys *keys)
> +				     const struct ptrauth_keys_user *keys)
>  {
>  	ukeys->apgakey = pac_key_to_user(&keys->apga);
>  }
>  
> -static void pac_generic_keys_from_user(struct ptrauth_keys *keys,
> +static void pac_generic_keys_from_user(struct ptrauth_keys_user *keys,
>  				       const struct user_pac_generic_keys *ukeys)
>  {
>  	keys->apga = pac_key_from_user(ukeys->apgakey);
> @@ -1059,7 +1059,7 @@ static int pac_generic_keys_get(struct task_struct *target,
>  				unsigned int pos, unsigned int count,
>  				void *kbuf, void __user *ubuf)
>  {
> -	struct ptrauth_keys *keys = &target->thread.keys_user;
> +	struct ptrauth_keys_user *keys = &target->thread.keys_user;
>  	struct user_pac_generic_keys user_keys;
>  
>  	if (!system_supports_generic_auth())
> @@ -1076,7 +1076,7 @@ static int pac_generic_keys_set(struct task_struct *target,
>  				unsigned int pos, unsigned int count,
>  				const void *kbuf, const void __user *ubuf)
>  {
> -	struct ptrauth_keys *keys = &target->thread.keys_user;
> +	struct ptrauth_keys_user *keys = &target->thread.keys_user;
>  	struct user_pac_generic_keys user_keys;
>  	int ret;
>  
> -- 
> 2.7.4
> 

-- 
Kees Cook

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