From nobody Thu Nov 28 12:45:38 2024 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 629111CF29B; Tue, 1 Oct 2024 23:00:41 +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=1727823642; cv=none; b=fRisgdjlMc9uFiFCAUyd3UD7vUU6uocU4TIc40Pp//cGTsDpBfUYxn7kIUEu5aq09Ws1zU2RhI3Uzo+uXVeuSsWoHryWtRo1Q8g/6WKR9VsF1g2uimcyohRJuj4I9zXBaWHUb9yQAN2K1UZ9PfzBfy+to3uOZ/GJXW3IwgMwITI= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1727823642; c=relaxed/simple; bh=QzHtuVcSDaL4Yx9qwbzgbMXiTjYft30F6+HnraYB7I8=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=SuLqqPBVc23wt0wy66dfpvNBAhzk30EOwvJ18HDj2wHVY6a9y3k3XZcb56aoyicP2+LmHbgmI4MlsfzkbOHcaQwYFtek0jYjgKHaPaotkgY7uBOdXjk1UuzJNDZ4UobdEVDMcfSr+85W5KEzRArBAaFnzFY4nz/TKWqFVW0Trdo= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=uZYeamrV; 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="uZYeamrV" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8E63EC4CECF; Tue, 1 Oct 2024 23:00:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1727823641; bh=QzHtuVcSDaL4Yx9qwbzgbMXiTjYft30F6+HnraYB7I8=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=uZYeamrVp2rmyMCQnluYwOnDm4n+Ff//3VOK9nh7fhijWFZSBsIrKKDjAGk/o56ph TWtU7syb9yzkhscU782HgCKBmfTe8umJChkH7pbpdmrFkFnZKDzEigjtf2MH4Q6h+p 03C4A6BM0Yce+YT95YTjNz7OxrDfGQse/whSczqePqSDu3R0HqcStk54Lkhz+mQEEG /g6Czt7bYJqEty6YzhPgcA7W0BO47QcNZGVJ0ID0LvsSGOrdMO4RtMtauP6xRfcUf3 TqTDwfiQYc3f0nkcAQpIFVMpBhb6kHSmTpoI4+YPQ4WcHzjP2Dcp9wdpT1PpFQ1JyR PZHhD65WC/Q5Q== From: Mark Brown Date: Tue, 01 Oct 2024 23:58:43 +0100 Subject: [PATCH v13 04/40] prctl: arch-agnostic prctl for shadow stack Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20241001-arm64-gcs-v13-4-222b78d87eee@kernel.org> References: <20241001-arm64-gcs-v13-0-222b78d87eee@kernel.org> In-Reply-To: <20241001-arm64-gcs-v13-0-222b78d87eee@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 , David Spickett , Yury Khrustalev , Wilco Dijkstra , 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 0.15-dev-99b12 X-Developer-Signature: v=1; a=openpgp-sha256; l=4975; i=broonie@kernel.org; h=from:subject:message-id; bh=QzHtuVcSDaL4Yx9qwbzgbMXiTjYft30F6+HnraYB7I8=; b=owEBbQGS/pANAwAKASTWi3JdVIfQAcsmYgBm/H7HehyHHZF6+cj8DJo6NxY+7EGNDDBamzVyHc5d IEYLGoqJATMEAAEKAB0WIQSt5miqZ1cYtZ/in+ok1otyXVSH0AUCZvx+xwAKCRAk1otyXVSH0JhiB/ wO8/ZF+SkRw9d5n/x/2zuP6kLyixcTZ3zAcm+iDEAW8JePX4d66upSGjkAXNAIOYliNpblNkRnl9lW /pqQ7K6QEeMennahYz0YD8lnH71QpGSZoYU4Q3TSyJu1ZMKTYlrBAd4xIFAjtTa1dsVtHWMbgc7EYT GrpwH5cRB82KnH5mEWaCdoBopZsgFWmMql5OS4Dhig4w/zyRuEBRoxmlgvQxdF3TWFrXD9i1lNVpHx CCKN9fjW0cokoWtvsnRvMxrlBAUb+FeHgux5A6Y+EjNCDrNy3dUev6djW59zf6sdiH/eXUqnNhum7i C/teDyY09NlgqHrpdzubJx7yX0COoy 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 Reviewed-by: Catalin Marinas Acked-by: Yury Khrustalev Signed-off-by: Mark Brown Reviewed-by: Deepak Gupta --- 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 182bad0c55df..56654306a832 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -4221,4 +4221,8 @@ static inline void pgalloc_tag_copy(struct folio *new= , struct folio *old) } #endif /* CONFIG_MEM_ALLOC_PROFILING */ =20 +int arch_get_shadow_stack_status(struct task_struct *t, unsigned long __us= er *status); +int arch_set_shadow_stack_status(struct task_struct *t, unsigned long stat= us); +int arch_lock_shadow_stack_status(struct task_struct *t, unsigned long sta= tus); + #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 =20 +/* + * 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 4da31f28fda8..3d38a9c7c5c9 100644 --- a/kernel/sys.c +++ b/kernel/sys.c @@ -2324,6 +2324,21 @@ int __weak arch_prctl_spec_ctrl_set(struct task_stru= ct *t, unsigned long which, return -EINVAL; } =20 +int __weak arch_get_shadow_stack_status(struct task_struct *t, unsigned lo= ng __user *status) +{ + return -EINVAL; +} + +int __weak arch_set_shadow_stack_status(struct task_struct *t, unsigned lo= ng status) +{ + return -EINVAL; +} + +int __weak arch_lock_shadow_stack_status(struct task_struct *t, unsigned l= ong status) +{ + return -EINVAL; +} + #define PR_IO_FLUSHER (PF_MEMALLOC_NOIO | PF_LOCAL_THROTTLE) =20 #ifdef CONFIG_ANON_VMA_NAME @@ -2784,6 +2799,21 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, a= rg2, unsigned long, arg3, case PR_RISCV_SET_ICACHE_FLUSH_CTX: error =3D RISCV_SET_ICACHE_FLUSH_CTX(arg2, arg3); break; + case PR_GET_SHADOW_STACK_STATUS: + if (arg3 || arg4 || arg5) + return -EINVAL; + error =3D arch_get_shadow_stack_status(me, (unsigned long __user *) arg2= ); + break; + case PR_SET_SHADOW_STACK_STATUS: + if (arg3 || arg4 || arg5) + return -EINVAL; + error =3D arch_set_shadow_stack_status(me, arg2); + break; + case PR_LOCK_SHADOW_STACK_STATUS: + if (arg3 || arg4 || arg5) + return -EINVAL; + error =3D arch_lock_shadow_stack_status(me, arg2); + break; default: error =3D -EINVAL; break; --=20 2.39.2