| Message ID | 653598b3cfcd80f0cc69f72a214e156bb1afde68.1561386715.git.andreyknvl@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | arm64: untag user pointers passed to the kernel | expand |
On Mon, Jun 24, 2019 at 04:32:47PM +0200, Andrey Konovalov wrote: > From: Catalin Marinas <catalin.marinas@arm.com> > > It is not desirable to relax the ABI to allow tagged user addresses into > the kernel indiscriminately. This patch introduces a prctl() interface > for enabling or disabling the tagged ABI with a global sysctl control > for preventing applications from enabling the relaxed ABI (meant for > testing user-space prctl() return error checking without reconfiguring > the kernel). The ABI properties are inherited by threads of the same > application and fork()'ed children but cleared on execve(). A Kconfig > option allows the overall disabling of the relaxed ABI. > > The PR_SET_TAGGED_ADDR_CTRL will be expanded in the future to handle > MTE-specific settings like imprecise vs precise exceptions. > > Signed-off-by: Catalin Marinas <catalin.marinas@arm.com> Reviewed-by: Kees Cook <keescook@chromium.org> -Kees > Signed-off-by: Andrey Konovalov <andreyknvl@google.com> > --- > arch/arm64/Kconfig | 9 ++++ > arch/arm64/include/asm/processor.h | 8 ++++ > arch/arm64/include/asm/thread_info.h | 1 + > arch/arm64/include/asm/uaccess.h | 4 +- > arch/arm64/kernel/process.c | 72 ++++++++++++++++++++++++++++ > include/uapi/linux/prctl.h | 5 ++ > kernel/sys.c | 12 +++++ > 7 files changed, 110 insertions(+), 1 deletion(-) > > diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig > index 697ea0510729..55fbaf20af2d 100644 > --- a/arch/arm64/Kconfig > +++ b/arch/arm64/Kconfig > @@ -1107,6 +1107,15 @@ config ARM64_SW_TTBR0_PAN > zeroed area and reserved ASID. The user access routines > restore the valid TTBR0_EL1 temporarily. > > +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 COMPAT > bool "Kernel support for 32-bit EL0" > depends on ARM64_4K_PAGES || EXPERT > diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/processor.h > index fd5b1a4efc70..ee86070a28d4 100644 > --- a/arch/arm64/include/asm/processor.h > +++ b/arch/arm64/include/asm/processor.h > @@ -296,6 +296,14 @@ extern void __init minsigstksz_setup(void); > /* PR_PAC_RESET_KEYS prctl */ > #define PAC_RESET_KEYS(tsk, arg) ptrauth_prctl_reset_keys(tsk, arg) > > +#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 2372e97db29c..4f81c4f15404 100644 > --- a/arch/arm64/include/asm/thread_info.h > +++ b/arch/arm64/include/asm/thread_info.h > @@ -88,6 +88,7 @@ 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 a138e3b4f717..097d6bfac0b7 100644 > --- a/arch/arm64/include/asm/uaccess.h > +++ b/arch/arm64/include/asm/uaccess.h > @@ -62,7 +62,9 @@ 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 9856395ccdb7..60e70158a4a1 100644 > --- a/arch/arm64/kernel/process.c > +++ b/arch/arm64/kernel/process.c > @@ -19,6 +19,7 @@ > #include <linux/kernel.h> > #include <linux/mm.h> > #include <linux/stddef.h> > +#include <linux/sysctl.h> > #include <linux/unistd.h> > #include <linux/user.h> > #include <linux/delay.h> > @@ -307,11 +308,18 @@ 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) > @@ -541,3 +549,67 @@ void arch_setup_new_exec(void) > > ptrauth_thread_init_user(current); > } > + > +#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 094bb03b9cc2..2e927b3e9d6c 100644 > --- a/include/uapi/linux/prctl.h > +++ b/include/uapi/linux/prctl.h > @@ -229,4 +229,9 @@ struct prctl_mm_map { > # define PR_PAC_APDBKEY (1UL << 3) > # define PR_PAC_APGAKEY (1UL << 4) > > +/* 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 2969304c29fe..c6c4d5358bd3 100644 > --- a/kernel/sys.c > +++ b/kernel/sys.c > @@ -124,6 +124,12 @@ > #ifndef PAC_RESET_KEYS > # define PAC_RESET_KEYS(a, b) (-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 > @@ -2492,6 +2498,12 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3, > return -EINVAL; > error = PAC_RESET_KEYS(me, arg2); > 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; > -- > 2.22.0.410.gd8fdbe21b5-goog >
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index 697ea0510729..55fbaf20af2d 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -1107,6 +1107,15 @@ config ARM64_SW_TTBR0_PAN zeroed area and reserved ASID. The user access routines restore the valid TTBR0_EL1 temporarily. +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 COMPAT bool "Kernel support for 32-bit EL0" depends on ARM64_4K_PAGES || EXPERT diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/processor.h index fd5b1a4efc70..ee86070a28d4 100644 --- a/arch/arm64/include/asm/processor.h +++ b/arch/arm64/include/asm/processor.h @@ -296,6 +296,14 @@ extern void __init minsigstksz_setup(void); /* PR_PAC_RESET_KEYS prctl */ #define PAC_RESET_KEYS(tsk, arg) ptrauth_prctl_reset_keys(tsk, arg) +#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 2372e97db29c..4f81c4f15404 100644 --- a/arch/arm64/include/asm/thread_info.h +++ b/arch/arm64/include/asm/thread_info.h @@ -88,6 +88,7 @@ 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 a138e3b4f717..097d6bfac0b7 100644 --- a/arch/arm64/include/asm/uaccess.h +++ b/arch/arm64/include/asm/uaccess.h @@ -62,7 +62,9 @@ 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 9856395ccdb7..60e70158a4a1 100644 --- a/arch/arm64/kernel/process.c +++ b/arch/arm64/kernel/process.c @@ -19,6 +19,7 @@ #include <linux/kernel.h> #include <linux/mm.h> #include <linux/stddef.h> +#include <linux/sysctl.h> #include <linux/unistd.h> #include <linux/user.h> #include <linux/delay.h> @@ -307,11 +308,18 @@ 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) @@ -541,3 +549,67 @@ void arch_setup_new_exec(void) ptrauth_thread_init_user(current); } + +#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 094bb03b9cc2..2e927b3e9d6c 100644 --- a/include/uapi/linux/prctl.h +++ b/include/uapi/linux/prctl.h @@ -229,4 +229,9 @@ struct prctl_mm_map { # define PR_PAC_APDBKEY (1UL << 3) # define PR_PAC_APGAKEY (1UL << 4) +/* 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 2969304c29fe..c6c4d5358bd3 100644 --- a/kernel/sys.c +++ b/kernel/sys.c @@ -124,6 +124,12 @@ #ifndef PAC_RESET_KEYS # define PAC_RESET_KEYS(a, b) (-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 @@ -2492,6 +2498,12 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3, return -EINVAL; error = PAC_RESET_KEYS(me, arg2); 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;