From: Kristina Martsenko kristina.martsenko@arm.com
mainline inclusion from v4.20-rc3 commit ba8308856564 category: feature bugzilla: 27615 CVE: NA
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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: Kristina Martsenko kristina.martsenko@arm.com Signed-off-by: Will Deacon will.deacon@arm.com
Conflicts: arch/arm64/kernel/Makefile [Zheng Zengkai: adjust context]
Signed-off-by: Zheng Zengkai zhengzengkai@huawei.com Reviewed-by: Hanjun Guo guohanjun@huawei.com Signed-off-by: Yang Yingliang yangyingliang@huawei.com --- arch/arm64/include/asm/pointer_auth.h | 3 ++ arch/arm64/include/asm/processor.h | 4 +++ arch/arm64/kernel/Makefile | 1 + arch/arm64/kernel/pointer_auth.c | 47 +++++++++++++++++++++++++++ include/uapi/linux/prctl.h | 8 +++++ kernel/sys.c | 8 +++++ 6 files changed, 71 insertions(+) create mode 100644 arch/arm64/kernel/pointer_auth.c
diff --git a/arch/arm64/include/asm/pointer_auth.h b/arch/arm64/include/asm/pointer_auth.h index 70b3996f00cc9..55cc128b9a81e 100644 --- a/arch/arm64/include/asm/pointer_auth.h +++ b/arch/arm64/include/asm/pointer_auth.h @@ -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) diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/processor.h index 7695a5117ff20..79a9df5b767c1 100644 --- a/arch/arm64/include/asm/processor.h +++ b/arch/arm64/include/asm/processor.h @@ -54,6 +54,7 @@ #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>
@@ -299,6 +300,9 @@ 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 * diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile index 24a9efdc2103e..1c9e374821f67 100644 --- a/arch/arm64/kernel/Makefile +++ b/arch/arm64/kernel/Makefile @@ -65,6 +65,7 @@ arm64-obj-$(CONFIG_ARM_SDE_INTERFACE) += sdei.o arm64-obj-$(CONFIG_ARM64_SSBD) += ssbd.o arm64-obj-$(CONFIG_SDEI_WATCHDOG) += watchdog_sdei.o arm64-obj-$(CONFIG_MPAM) += mpam.o mpam_ctrlmon.o mpam_mon.o +arm64-obj-$(CONFIG_ARM64_PTR_AUTH) += pointer_auth.o
obj-y += $(arm64-obj-y) vdso/ probes/ obj-$(CONFIG_ARM64_ILP32) += vdso-ilp32/ diff --git a/arch/arm64/kernel/pointer_auth.c b/arch/arm64/kernel/pointer_auth.c new file mode 100644 index 0000000000000..b9f6f5f3409a5 --- /dev/null +++ b/arch/arm64/kernel/pointer_auth.c @@ -0,0 +1,47 @@ +// 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; +} diff --git a/include/uapi/linux/prctl.h b/include/uapi/linux/prctl.h index b17201edfa09a..b4875a93363a9 100644 --- a/include/uapi/linux/prctl.h +++ b/include/uapi/linux/prctl.h @@ -220,4 +220,12 @@ 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 */ diff --git a/kernel/sys.c b/kernel/sys.c index 827289a347765..9452f8d3ef5ec 100644 --- a/kernel/sys.c +++ b/kernel/sys.c @@ -121,6 +121,9 @@ #ifndef SVE_GET_VL # define SVE_GET_VL() (-EINVAL) #endif +#ifndef PAC_RESET_KEYS +# define PAC_RESET_KEYS(a, b) (-EINVAL) +#endif
/* * this is where the system-wide overflow UID and GID are defined, for @@ -2483,6 +2486,11 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3, return -EINVAL; error = arch_prctl_spec_ctrl_set(me, arg2, arg3); break; + case PR_PAC_RESET_KEYS: + if (arg3 || arg4 || arg5) + return -EINVAL; + error = PAC_RESET_KEYS(me, arg2); + break; default: error = -EINVAL; break;