From patchwork Tue Jun 25 14:57:30 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mark Brown X-Patchwork-Id: 13711316 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 100CE16DEA4; Tue, 25 Jun 2024 15:00:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1719327655; cv=none; b=H671euYi9gXTffoagwv7vxMW37pqgOZbRlj6N/ASXoVQL8Y579iBIgivs4e3XEPXoEeFqAvQk/9XjRUn1b11EJTmwPd/gRYxikwY/WtAMgu05sxYD4oddfZU/SRdhqlsETAJeYPYgXcwmDOM0aOFlzD8hD37y0b1g2TBs7HkKgk= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1719327655; c=relaxed/simple; bh=xJ9t4tbxjPWwdEXN7AJPy8EkOPvqUrrpN3dVrptIv5g=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=MwC+pWoa4j7sbOP54IMs/wMYnC8vvowRcRTPquDm/bcivt3avFGBStlDegNe5UZYhLgP6FH7jTQhh9VTpXrh8d2X8iBoItvNdGIt3jbWVMSYN6F+dARJKvCoBmBtl7bJSQrr6Rnswo8Q1aPoneDu06907SpeH1EPXnCcHJh8P58= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=iq38Clbz; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="iq38Clbz" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2B2D7C32781; Tue, 25 Jun 2024 15:00:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1719327654; bh=xJ9t4tbxjPWwdEXN7AJPy8EkOPvqUrrpN3dVrptIv5g=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=iq38Clbz1hHfoKc/wSZZk2BlQ/mzhSjhrLiA22m0q1FADk2R8NduGL9CtpxdE3zfc Jta17wr/D9HMP1ARNRvCP0Viqb4rSdbiNxuZQhnAjP5Jb29A6CyazGpm5O3GV69jx8 6hEcnHSVlTvtjPcoLw+NYCnIDmU78emIwCnf66whyp26i7DcG1bERn7A49wpmurqL4 uBfPOMJxK7wRhjchjrCY7olbYHH0FONp2kBM0d2FvxGN2z3ok8sTfS7qHlN6PAldGY WUzG7tr12MDHFTK+y+EYKp/vxrD21Ux3ZdzMr/t9JcuPZ/TM4qh8Q0TkcakZ363p3a c5srk9ZdAG+eg== From: Mark Brown Date: Tue, 25 Jun 2024 15:57:30 +0100 Subject: [PATCH v9 02/39] prctl: arch-agnostic prctl for shadow stack Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Message-Id: <20240625-arm64-gcs-v9-2-0f634469b8f0@kernel.org> References: <20240625-arm64-gcs-v9-0-0f634469b8f0@kernel.org> In-Reply-To: <20240625-arm64-gcs-v9-0-0f634469b8f0@kernel.org> To: Catalin Marinas , Will Deacon , Jonathan Corbet , Andrew Morton , Marc Zyngier , Oliver Upton , James Morse , Suzuki K Poulose , Arnd Bergmann , Oleg Nesterov , Eric Biederman , Shuah Khan , "Rick P. Edgecombe" , Deepak Gupta , Ard Biesheuvel , Szabolcs Nagy , Kees Cook Cc: "H.J. Lu" , Paul Walmsley , Palmer Dabbelt , Albert Ou , Florian Weimer , Christian Brauner , Thiago Jung Bauermann , Ross Burton , linux-arm-kernel@lists.infradead.org, linux-doc@vger.kernel.org, kvmarm@lists.linux.dev, linux-fsdevel@vger.kernel.org, linux-arch@vger.kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org, Mark Brown X-Mailer: b4 0.14-dev-d4707 X-Developer-Signature: v=1; a=openpgp-sha256; l=4925; i=broonie@kernel.org; h=from:subject:message-id; bh=xJ9t4tbxjPWwdEXN7AJPy8EkOPvqUrrpN3dVrptIv5g=; b=owEBbQGS/pANAwAKASTWi3JdVIfQAcsmYgBmettzm06Y7iTf+FNBBKI/e4XfSTUxczl0dim7vJR4 HzPqY+mJATMEAAEKAB0WIQSt5miqZ1cYtZ/in+ok1otyXVSH0AUCZnrbcwAKCRAk1otyXVSH0NGTB/ 47xIkH+crEklE5tZJwII1usQp9/PxNfFycXYIe4bAwnF70KSEO4bbwXI9w/M12yzcBsdHrQkJvj02v VNsNl074a53gnQuXxBfu1gWQeaopApABUjzGPgf2Iy0lmtBj0VViuhorXNlbhOZMRtuMZzWaw/bRxH aTVtePDPYNZ+JosCdRpomOyi9yeN5/8ShqI5r3xmiBuzhKSITzSrOqj+7nq+lsthAhqiDtf4J6j+l4 RGkYUrlS4WSfdnX5bXJh/QtHHlXBpt0g6uRPNR8Ezh2iG4i5mYJuLd9w1A94uPLM+fmAj1SQeeNloH hiMikorgRQJgQa63sa7a2OmRhSi/Yj X-Developer-Key: i=broonie@kernel.org; a=openpgp; fpr=3F2568AAC26998F9E813A1C5C3F436CA30F5D8EB Three architectures (x86, aarch64, riscv) have announced support for shadow stacks with fairly similar functionality. While x86 is using arch_prctl() to control the functionality neither arm64 nor riscv uses that interface so this patch adds arch-agnostic prctl() support to get and set status of shadow stacks and lock the current configuation to prevent further changes, with support for turning on and off individual subfeatures so applications can limit their exposure to features that they do not need. The features are: - PR_SHADOW_STACK_ENABLE: Tracking and enforcement of shadow stacks, including allocation of a shadow stack if one is not already allocated. - PR_SHADOW_STACK_WRITE: Writes to specific addresses in the shadow stack. - PR_SHADOW_STACK_PUSH: Push additional values onto the shadow stack. These features are expected to be inherited by new threads and cleared on exec(), unknown features should be rejected for enable but accepted for locking (in order to allow for future proofing). This is based on a patch originally written by Deepak Gupta but modified fairly heavily, support for indirect landing pads is removed, additional modes added and the locking interface reworked. The set status prctl() is also reworked to just set flags, if setting/reading the shadow stack pointer is required this could be a separate prctl. Reviewed-by: Thiago Jung Bauermann Signed-off-by: Mark Brown --- include/linux/mm.h | 4 ++++ include/uapi/linux/prctl.h | 22 ++++++++++++++++++++++ kernel/sys.c | 30 ++++++++++++++++++++++++++++++ 3 files changed, 56 insertions(+) diff --git a/include/linux/mm.h b/include/linux/mm.h index 5ec7bc355657..120abcfaf974 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -4263,4 +4263,8 @@ static inline bool pfn_is_unaccepted_memory(unsigned long pfn) void vma_pgtable_walk_begin(struct vm_area_struct *vma); void vma_pgtable_walk_end(struct vm_area_struct *vma); +int arch_get_shadow_stack_status(struct task_struct *t, unsigned long __user *status); +int arch_set_shadow_stack_status(struct task_struct *t, unsigned long status); +int arch_lock_shadow_stack_status(struct task_struct *t, unsigned long status); + #endif /* _LINUX_MM_H */ diff --git a/include/uapi/linux/prctl.h b/include/uapi/linux/prctl.h index 35791791a879..557a3d2ac1d4 100644 --- a/include/uapi/linux/prctl.h +++ b/include/uapi/linux/prctl.h @@ -328,4 +328,26 @@ struct prctl_mm_map { # define PR_PPC_DEXCR_CTRL_CLEAR_ONEXEC 0x10 /* Clear the aspect on exec */ # define PR_PPC_DEXCR_CTRL_MASK 0x1f +/* + * Get the current shadow stack configuration for the current thread, + * this will be the value configured via PR_SET_SHADOW_STACK_STATUS. + */ +#define PR_GET_SHADOW_STACK_STATUS 74 + +/* + * Set the current shadow stack configuration. Enabling the shadow + * stack will cause a shadow stack to be allocated for the thread. + */ +#define PR_SET_SHADOW_STACK_STATUS 75 +# define PR_SHADOW_STACK_ENABLE (1UL << 0) +# define PR_SHADOW_STACK_WRITE (1UL << 1) +# define PR_SHADOW_STACK_PUSH (1UL << 2) + +/* + * Prevent further changes to the specified shadow stack + * configuration. All bits may be locked via this call, including + * undefined bits. + */ +#define PR_LOCK_SHADOW_STACK_STATUS 76 + #endif /* _LINUX_PRCTL_H */ diff --git a/kernel/sys.c b/kernel/sys.c index 3a2df1bd9f64..7e0c10e867cf 100644 --- a/kernel/sys.c +++ b/kernel/sys.c @@ -2324,6 +2324,21 @@ int __weak arch_prctl_spec_ctrl_set(struct task_struct *t, unsigned long which, return -EINVAL; } +int __weak arch_get_shadow_stack_status(struct task_struct *t, unsigned long __user *status) +{ + return -EINVAL; +} + +int __weak arch_set_shadow_stack_status(struct task_struct *t, unsigned long status) +{ + return -EINVAL; +} + +int __weak arch_lock_shadow_stack_status(struct task_struct *t, unsigned long status) +{ + return -EINVAL; +} + #define PR_IO_FLUSHER (PF_MEMALLOC_NOIO | PF_LOCAL_THROTTLE) #ifdef CONFIG_ANON_VMA_NAME @@ -2782,6 +2797,21 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3, case PR_RISCV_SET_ICACHE_FLUSH_CTX: error = RISCV_SET_ICACHE_FLUSH_CTX(arg2, arg3); break; + case PR_GET_SHADOW_STACK_STATUS: + if (arg3 || arg4 || arg5) + return -EINVAL; + error = arch_get_shadow_stack_status(me, (unsigned long __user *) arg2); + break; + case PR_SET_SHADOW_STACK_STATUS: + if (arg3 || arg4 || arg5) + return -EINVAL; + error = arch_set_shadow_stack_status(me, arg2); + break; + case PR_LOCK_SHADOW_STACK_STATUS: + if (arg3 || arg4 || arg5) + return -EINVAL; + error = arch_lock_shadow_stack_status(me, arg2); + break; default: error = -EINVAL; break;