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[217.140.110.172]) by mx.google.com with ESMTP id j2si71358ejm.114.2019.06.12.07.30.50 for ; Wed, 12 Jun 2019 07:30:50 -0700 (PDT) Received-SPF: pass (google.com: domain of vincenzo.frascino@arm.com designates 217.140.110.172 as permitted sender) client-ip=217.140.110.172; Authentication-Results: mx.google.com; spf=pass (google.com: domain of vincenzo.frascino@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=vincenzo.frascino@arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id B7BE32B; Wed, 12 Jun 2019 07:30:49 -0700 (PDT) Received: from [10.1.196.72] (e119884-lin.cambridge.arm.com [10.1.196.72]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 08D163F557; Wed, 12 Jun 2019 07:30:44 -0700 (PDT) Subject: Re: [PATCH v17 03/15] arm64: Introduce prctl() options to control the tagged user addresses ABI To: Andrey Konovalov , linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, amd-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-rdma@vger.kernel.org, linux-media@vger.kernel.org, kvm@vger.kernel.org, linux-kselftest@vger.kernel.org Cc: Catalin Marinas , Will Deacon , Mark Rutland , Andrew Morton , Greg Kroah-Hartman , Kees Cook , Yishai Hadas , Felix Kuehling , Alexander Deucher , Christian Koenig , Mauro Carvalho Chehab , Jens Wiklander , Alex Williamson , Leon Romanovsky , Luc Van Oostenryck , Dave Martin , Khalid Aziz , enh , Jason Gunthorpe , Christoph Hellwig , Dmitry Vyukov , Kostya Serebryany , Evgeniy Stepanov , Lee Smith , Ramana Radhakrishnan , Jacob Bramley , Ruben Ayrapetyan , Robin Murphy , Kevin Brodsky , Szabolcs Nagy References: From: Vincenzo Frascino Message-ID: <71ed41e2-47b8-3410-e759-21d972b7a33d@arm.com> Date: Wed, 12 Jun 2019 15:30:44 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 12/06/2019 12:43, Andrey Konovalov wrote: > From: Catalin Marinas > > 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(). > > 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 Reviewed-by: Vincenzo Frascino > --- > arch/arm64/include/asm/processor.h | 6 +++ > arch/arm64/include/asm/thread_info.h | 1 + > arch/arm64/include/asm/uaccess.h | 3 +- > arch/arm64/kernel/process.c | 67 ++++++++++++++++++++++++++++ > include/uapi/linux/prctl.h | 5 +++ > kernel/sys.c | 16 +++++++ > 6 files changed, 97 insertions(+), 1 deletion(-) > > diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/processor.h > index fcd0e691b1ea..fee457456aa8 100644 > --- a/arch/arm64/include/asm/processor.h > +++ b/arch/arm64/include/asm/processor.h > @@ -307,6 +307,12 @@ extern void __init minsigstksz_setup(void); > /* PR_PAC_RESET_KEYS prctl */ > #define PAC_RESET_KEYS(tsk, arg) ptrauth_prctl_reset_keys(tsk, arg) > > +/* PR_TAGGED_ADDR 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() > + > /* > * For CONFIG_GCC_PLUGIN_STACKLEAK > * > diff --git a/arch/arm64/include/asm/thread_info.h b/arch/arm64/include/asm/thread_info.h > index f1d032be628a..354a31d2b737 100644 > --- a/arch/arm64/include/asm/thread_info.h > +++ b/arch/arm64/include/asm/thread_info.h > @@ -99,6 +99,7 @@ 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 df729afca0ba..995b9ea11a89 100644 > --- a/arch/arm64/include/asm/uaccess.h > +++ b/arch/arm64/include/asm/uaccess.h > @@ -73,7 +73,8 @@ 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 (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 3767fb21a5b8..69d0be1fc708 100644 > --- a/arch/arm64/kernel/process.c > +++ b/arch/arm64/kernel/process.c > @@ -30,6 +30,7 @@ > #include > #include > #include > +#include > #include > #include > #include > @@ -323,6 +324,7 @@ void flush_thread(void) > fpsimd_flush_thread(); > tls_thread_flush(); > flush_ptrace_hw_breakpoint(current); > + clear_thread_flag(TIF_TAGGED_ADDR); > } > > void release_thread(struct task_struct *dead_task) > @@ -552,3 +554,68 @@ void arch_setup_new_exec(void) > > ptrauth_thread_init_user(current); > } > + > +/* > + * 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; > + > + if (arg & PR_TAGGED_ADDR_ENABLE) > + set_thread_flag(TIF_TAGGED_ADDR); > + else > + clear_thread_flag(TIF_TAGGED_ADDR); > + > + 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); > 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..ec48396b4943 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 +2498,16 @@ 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: > + if (arg3 || arg4 || arg5) > + return -EINVAL; > + error = SET_TAGGED_ADDR_CTRL(arg2); > + break; > + case PR_GET_TAGGED_ADDR_CTRL: > + if (arg2 || arg3 || arg4 || arg5) > + return -EINVAL; > + error = GET_TAGGED_ADDR_CTRL(); > + break; > default: > error = -EINVAL; > break; > -- Regards, Vincenzo