diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index 0552d3a00ea9..4503040a8081 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -964,6 +964,15 @@ config ARM64_SSBD If unsure, say Y. +config ARM64_TAGGED_ADDR_ABI + bool "Enable the tagged user addresses syscall ABI" + default y + help + When this option is enabled, user applications can opt in to a + relaxed ABI via prctl() allowing tagged addresses to be passed + to system calls as pointer arguments. For details, see + Documentation/arm64/tagged-address-abi.txt. + menuconfig ARMV8_DEPRECATED bool "Emulate deprecated/obsolete ARMv8 instructions" depends on COMPAT diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/processor.h index def5a5e807f0..4a6931985575 100644 --- a/arch/arm64/include/asm/processor.h +++ b/arch/arm64/include/asm/processor.h @@ -274,6 +274,14 @@ extern void __init minsigstksz_setup(void); #define SVE_SET_VL(arg) sve_set_current_vl(arg) #define SVE_GET_VL() sve_get_current_vl() +#ifdef CONFIG_ARM64_TAGGED_ADDR_ABI +/* PR_{SET,GET}_TAGGED_ADDR_CTRL prctl */ +long set_tagged_addr_ctrl(unsigned long arg); +long get_tagged_addr_ctrl(void); +#define SET_TAGGED_ADDR_CTRL(arg) set_tagged_addr_ctrl(arg) +#define GET_TAGGED_ADDR_CTRL() get_tagged_addr_ctrl() +#endif + /* * For CONFIG_GCC_PLUGIN_STACKLEAK * diff --git a/arch/arm64/include/asm/thread_info.h b/arch/arm64/include/asm/thread_info.h index cb2c10a8f0a8..974aa0ce4d8d 100644 --- a/arch/arm64/include/asm/thread_info.h +++ b/arch/arm64/include/asm/thread_info.h @@ -89,6 +89,7 @@ void arch_release_task_struct(struct task_struct *tsk); #define TIF_SVE 23 /* Scalable Vector Extension in use */ #define TIF_SVE_VL_INHERIT 24 /* Inherit sve_vl_onexec across exec */ #define TIF_SSBD 25 /* Wants SSB mitigation */ +#define TIF_TAGGED_ADDR 26 /* Allow tagged user addresses */ #define _TIF_SIGPENDING (1 << TIF_SIGPENDING) #define _TIF_NEED_RESCHED (1 << TIF_NEED_RESCHED) diff --git a/arch/arm64/include/asm/uaccess.h b/arch/arm64/include/asm/uaccess.h index 3f52fbcaf62d..065ab9cd4767 100644 --- a/arch/arm64/include/asm/uaccess.h +++ b/arch/arm64/include/asm/uaccess.h @@ -76,7 +76,9 @@ static inline unsigned long __range_ok(const void __user *addr, unsigned long si { unsigned long ret, limit = current_thread_info()->addr_limit; - addr = untagged_addr(addr); + if (IS_ENABLED(CONFIG_ARM64_TAGGED_ADDR_ABI) && + test_thread_flag(TIF_TAGGED_ADDR)) + addr = untagged_addr(addr); __chk_user_ptr(addr); asm volatile( diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c index 7f1628effe6d..f6940b28fe74 100644 --- a/arch/arm64/kernel/process.c +++ b/arch/arm64/kernel/process.c @@ -30,6 +30,7 @@ #include #include #include +#include #include #include #include @@ -49,6 +50,7 @@ #include #include #include +#include #include #include @@ -269,11 +271,18 @@ static void tls_thread_flush(void) } } +static void flush_tagged_addr_state(void) +{ + if (IS_ENABLED(CONFIG_ARM64_TAGGED_ADDR_ABI)) + clear_thread_flag(TIF_TAGGED_ADDR); +} + void flush_thread(void) { fpsimd_flush_thread(); tls_thread_flush(); flush_ptrace_hw_breakpoint(current); + flush_tagged_addr_state(); } void release_thread(struct task_struct *dead_task) @@ -515,3 +524,67 @@ void __used stackleak_check_alloca(unsigned long size) } EXPORT_SYMBOL(stackleak_check_alloca); #endif + +#ifdef CONFIG_ARM64_TAGGED_ADDR_ABI +/* + * Control the relaxed ABI allowing tagged user addresses into the kernel. + */ +static unsigned int tagged_addr_prctl_allowed = 1; + +long set_tagged_addr_ctrl(unsigned long arg) +{ + if (!tagged_addr_prctl_allowed) + return -EINVAL; + if (is_compat_task()) + return -EINVAL; + if (arg & ~PR_TAGGED_ADDR_ENABLE) + return -EINVAL; + + update_thread_flag(TIF_TAGGED_ADDR, arg & PR_TAGGED_ADDR_ENABLE); + + return 0; +} + +long get_tagged_addr_ctrl(void) +{ + if (!tagged_addr_prctl_allowed) + return -EINVAL; + if (is_compat_task()) + return -EINVAL; + + if (test_thread_flag(TIF_TAGGED_ADDR)) + return PR_TAGGED_ADDR_ENABLE; + + return 0; +} + +/* + * Global sysctl to disable the tagged user addresses support. This control + * only prevents the tagged address ABI enabling via prctl() and does not + * disable it for tasks that already opted in to the relaxed ABI. + */ +static int zero; +static int one = 1; + +static struct ctl_table tagged_addr_sysctl_table[] = { + { + .procname = "tagged_addr", + .mode = 0644, + .data = &tagged_addr_prctl_allowed, + .maxlen = sizeof(int), + .proc_handler = proc_dointvec_minmax, + .extra1 = &zero, + .extra2 = &one, + }, + { } +}; + +static int __init tagged_addr_init(void) +{ + if (!register_sysctl("abi", tagged_addr_sysctl_table)) + return -EINVAL; + return 0; +} + +core_initcall(tagged_addr_init); +#endif /* CONFIG_ARM64_TAGGED_ADDR_ABI */ diff --git a/include/uapi/linux/prctl.h b/include/uapi/linux/prctl.h index 5cdf23461174..9d34a5259014 100644 --- a/include/uapi/linux/prctl.h +++ b/include/uapi/linux/prctl.h @@ -223,4 +223,9 @@ struct prctl_mm_map { #define PR_SET_VMA 0x53564d41 # define PR_SET_VMA_ANON_NAME 0 +/* Tagged user address controls for arm64 */ +#define PR_SET_TAGGED_ADDR_CTRL 55 +#define PR_GET_TAGGED_ADDR_CTRL 56 +# define PR_TAGGED_ADDR_ENABLE (1UL << 0) + #endif /* _LINUX_PRCTL_H */ diff --git a/kernel/sys.c b/kernel/sys.c index 32b78d0aa03a..a052d071c712 100644 --- a/kernel/sys.c +++ b/kernel/sys.c @@ -123,6 +123,12 @@ #ifndef SVE_GET_VL # define SVE_GET_VL() (-EINVAL) #endif +#ifndef SET_TAGGED_ADDR_CTRL +# define SET_TAGGED_ADDR_CTRL(a) (-EINVAL) +#endif +#ifndef GET_TAGGED_ADDR_CTRL +# define GET_TAGGED_ADDR_CTRL() (-EINVAL) +#endif /* * this is where the system-wide overflow UID and GID are defined, for @@ -2628,6 +2634,12 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3, case PR_SET_VMA: error = prctl_set_vma(arg2, arg3, arg4, arg5); break; + case PR_SET_TAGGED_ADDR_CTRL: + error = SET_TAGGED_ADDR_CTRL(arg2); + break; + case PR_GET_TAGGED_ADDR_CTRL: + error = GET_TAGGED_ADDR_CTRL(); + break; default: error = -EINVAL; break;