From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 424CBD339AE for ; Fri, 5 Dec 2025 18:42:26 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id E66EA6B002D; Fri, 5 Dec 2025 13:41:59 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id D07F66B0031; Fri, 5 Dec 2025 13:41:59 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id BA9B46B002F; Fri, 5 Dec 2025 13:41:59 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id 93E726B028D for ; Fri, 5 Dec 2025 13:41:59 -0500 (EST) Received: from smtpin22.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay04.hostedemail.com (Postfix) with ESMTP id 5DE1E1A026F for ; Fri, 5 Dec 2025 18:41:59 +0000 (UTC) X-FDA: 84186286758.22.813AA2C Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf17.hostedemail.com (Postfix) with ESMTP id 52F624000B for ; Fri, 5 Dec 2025 18:41:57 +0000 (UTC) Authentication-Results: imf17.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=qHf2Fs9H; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf17.hostedemail.com: domain of devnull+debug.rivosinc.com@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=devnull+debug.rivosinc.com@kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1764960117; h=from:from:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=WYQCaogP1Esx6vaJsC/4o2UG7lEx16aXFTaBTkgr6JM=; b=Oz/uOhlS8pWZPcvAQQ/V9d3fru8Lo7a/mJkWyL8wXEzdpjJ3LZgdyTvpFQdnTA+wcG/G2c CK5HqpOE6+3fdgdvDEoyvFlhg+iF5h7pqtvCRUxwmhiuD/dNJLsqJjDvEi6+2viXOqjxzQ jNiv1Dw5oQokhPrFmDHeeMAeGx58pMw= ARC-Authentication-Results: i=1; imf17.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=qHf2Fs9H; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf17.hostedemail.com: domain of devnull+debug.rivosinc.com@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=devnull+debug.rivosinc.com@kernel.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1764960117; a=rsa-sha256; cv=none; b=w58Wtlp54MdV5o3REz/YSY77OZNwZwTdPromjHiyf2xKiMqWHH2YC6JkLCLo0Rvi3uecbw k2KZZSQ2z2j9pcDh3W18SJUM1X/Nm1yNEE0CBIZhLrAEIfSdNtbMB+JqxXqyAPEEgesmFg cQ91ebXBx2cGW2Qvcfu+F0qFn9dA27I= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sea.source.kernel.org (Postfix) with ESMTP id 5C57744562; Fri, 5 Dec 2025 18:41:51 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPS id 11A04C4DDE9; Fri, 5 Dec 2025 18:41:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1764960111; bh=YQg+XVHKEI/+k3SQ8JtN+2+b+t7JDDMJ08bQo4q+FJs=; h=From:Date:Subject:References:In-Reply-To:To:Cc:Reply-To:From; b=qHf2Fs9HeKiYvgNirXB8qle6VBZDbivLzqGw08CCA9ObjrDSP3VX8dR0xOZ88I+zi olpiool2K8FtajiAuIlifALoXiHHLJQyyVUI82VIDf0RU3H8pY7RAotgrdULChCtIp W31bsghz2Lo6g+ISIQXBL/xYO74cq3uRYBj2FLJa6BWtYXejQCR/pSLr8JyLbMM9E4 4L+/njrEjelaJ9WTf7tEZHBqvqquB+5ZvvV0uXMo4HNqIMzMr1J6fArX7Ix03w/DXT SE1HXyhCHitL8krzHcoy9rW2S+d8A044wrnLXa23hEdiOcSOG85G5evWs7NqFm8Svz lYc4oL6K1x+wQ== Received: from aws-us-west-2-korg-lkml-1.web.codeaurora.org (localhost.localdomain [127.0.0.1]) by smtp.lore.kernel.org (Postfix) with ESMTP id EE88BD339B7; Fri, 5 Dec 2025 18:41:50 +0000 (UTC) From: Deepak Gupta via B4 Relay Date: Fri, 05 Dec 2025 10:41:50 -0800 Subject: [PATCH v25 12/28] riscv: Implements arch agnostic shadow stack prctls MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20251205-v5_user_cfi_series-v25-12-1a07c0127361@rivosinc.com> References: <20251205-v5_user_cfi_series-v25-0-1a07c0127361@rivosinc.com> In-Reply-To: <20251205-v5_user_cfi_series-v25-0-1a07c0127361@rivosinc.com> To: Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Andrew Morton , "Liam R. Howlett" , Vlastimil Babka , Lorenzo Stoakes , Paul Walmsley , Palmer Dabbelt , Albert Ou , Conor Dooley , Rob Herring , Krzysztof Kozlowski , Arnd Bergmann , Christian Brauner , Peter Zijlstra , Oleg Nesterov , Eric Biederman , Kees Cook , Jonathan Corbet , Shuah Khan , Jann Horn , Conor Dooley , Miguel Ojeda , Alex Gaynor , Boqun Feng , Gary Guo , =?utf-8?q?Bj=C3=B6rn_Roy_Baron?= , Andreas Hindborg , Alice Ryhl , Trevor Gross , Benno Lossin Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-riscv@lists.infradead.org, devicetree@vger.kernel.org, linux-arch@vger.kernel.org, linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org, alistair.francis@wdc.com, richard.henderson@linaro.org, jim.shu@sifive.com, andybnac@gmail.com, kito.cheng@sifive.com, charlie@rivosinc.com, atishp@rivosinc.com, evan@rivosinc.com, cleger@rivosinc.com, alexghiti@rivosinc.com, samitolvanen@google.com, broonie@kernel.org, rick.p.edgecombe@intel.com, rust-for-linux@vger.kernel.org, Zong Li , Andreas Korb , Valentin Haudiquet , Deepak Gupta X-Mailer: b4 0.13.0 X-Developer-Signature: v=1; a=ed25519-sha256; t=1764960107; l=7555; i=debug@rivosinc.com; s=20251023; h=from:subject:message-id; bh=j8/8VvndI2qVQcHHX8TNZcByjmD2v9rRKoH3o+WjKYE=; b=yQo8xKfVejFOjeVogC+WjDAl+HIeSNzjrEq8DlGeKyZ1V0haFF+sZkhFWybxOwapnhbdvfCMk mmii7UZuUxpCNnGox14m2GjNjZxdNR65/SIONzNQGakGA912RgJLeGo X-Developer-Key: i=debug@rivosinc.com; a=ed25519; pk=O37GQv1thBhZToXyQKdecPDhtWVbEDRQ0RIndijvpjk= X-Endpoint-Received: by B4 Relay for debug@rivosinc.com/20251023 with auth_id=553 X-Original-From: Deepak Gupta Reply-To: debug@rivosinc.com X-Rspam-User: X-Stat-Signature: hdx3scba5sje7cdxuerdbyyma433gpi6 X-Rspamd-Queue-Id: 52F624000B X-Rspamd-Server: rspam06 X-HE-Tag: 1764960117-392026 X-HE-Meta: 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 WLuJyyhq 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 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: List-Subscribe: List-Unsubscribe: From: Deepak Gupta Implement architecture agnostic prctls() interface for setting and getting shadow stack status. prctls implemented are PR_GET_SHADOW_STACK_STATUS, PR_SET_SHADOW_STACK_STATUS and PR_LOCK_SHADOW_STACK_STATUS. As part of PR_SET_SHADOW_STACK_STATUS/PR_GET_SHADOW_STACK_STATUS, only PR_SHADOW_STACK_ENABLE is implemented because RISCV allows each mode to write to their own shadow stack using `sspush` or `ssamoswap`. PR_LOCK_SHADOW_STACK_STATUS locks current configuration of shadow stack enabling. Reviewed-by: Zong Li Tested-by: Andreas Korb Tested-by: Valentin Haudiquet Signed-off-by: Deepak Gupta --- arch/riscv/include/asm/usercfi.h | 16 ++++++ arch/riscv/kernel/process.c | 8 +++ arch/riscv/kernel/usercfi.c | 110 +++++++++++++++++++++++++++++++++++++++ 3 files changed, 134 insertions(+) diff --git a/arch/riscv/include/asm/usercfi.h b/arch/riscv/include/asm/usercfi.h index a16a5dff8b0e..d71093f414df 100644 --- a/arch/riscv/include/asm/usercfi.h +++ b/arch/riscv/include/asm/usercfi.h @@ -7,6 +7,7 @@ #ifndef __ASSEMBLER__ #include +#include struct task_struct; struct kernel_clone_args; @@ -14,6 +15,7 @@ struct kernel_clone_args; #ifdef CONFIG_RISCV_USER_CFI struct cfi_state { unsigned long ubcfi_en : 1; /* Enable for backward cfi. */ + unsigned long ubcfi_locked : 1; unsigned long user_shdw_stk; /* Current user shadow stack pointer */ unsigned long shdw_stk_base; /* Base address of shadow stack */ unsigned long shdw_stk_size; /* size of shadow stack */ @@ -26,6 +28,12 @@ void set_shstk_base(struct task_struct *task, unsigned long shstk_addr, unsigned unsigned long get_shstk_base(struct task_struct *task, unsigned long *size); void set_active_shstk(struct task_struct *task, unsigned long shstk_addr); bool is_shstk_enabled(struct task_struct *task); +bool is_shstk_locked(struct task_struct *task); +bool is_shstk_allocated(struct task_struct *task); +void set_shstk_lock(struct task_struct *task); +void set_shstk_status(struct task_struct *task, bool enable); + +#define PR_SHADOW_STACK_SUPPORTED_STATUS_MASK (PR_SHADOW_STACK_ENABLE) #else @@ -41,6 +49,14 @@ bool is_shstk_enabled(struct task_struct *task); #define is_shstk_enabled(task) false +#define is_shstk_locked(task) false + +#define is_shstk_allocated(task) false + +#define set_shstk_lock(task) do {} while (0) + +#define set_shstk_status(task, enable) do {} while (0) + #endif /* CONFIG_RISCV_USER_CFI */ #endif /* __ASSEMBLER__ */ diff --git a/arch/riscv/kernel/process.c b/arch/riscv/kernel/process.c index 72d35adc6e0e..a137d3483646 100644 --- a/arch/riscv/kernel/process.c +++ b/arch/riscv/kernel/process.c @@ -156,6 +156,14 @@ void start_thread(struct pt_regs *regs, unsigned long pc, regs->epc = pc; regs->sp = sp; + /* + * clear shadow stack state on exec. + * libc will set it later via prctl. + */ + set_shstk_status(current, false); + set_shstk_base(current, 0, 0); + set_active_shstk(current, 0); + #ifdef CONFIG_64BIT regs->status &= ~SR_UXL; diff --git a/arch/riscv/kernel/usercfi.c b/arch/riscv/kernel/usercfi.c index 872e0c52e034..0b77b812e4d7 100644 --- a/arch/riscv/kernel/usercfi.c +++ b/arch/riscv/kernel/usercfi.c @@ -24,6 +24,16 @@ bool is_shstk_enabled(struct task_struct *task) return task->thread_info.user_cfi_state.ubcfi_en; } +bool is_shstk_allocated(struct task_struct *task) +{ + return task->thread_info.user_cfi_state.shdw_stk_base; +} + +bool is_shstk_locked(struct task_struct *task) +{ + return task->thread_info.user_cfi_state.ubcfi_locked; +} + void set_shstk_base(struct task_struct *task, unsigned long shstk_addr, unsigned long size) { task->thread_info.user_cfi_state.shdw_stk_base = shstk_addr; @@ -42,6 +52,26 @@ void set_active_shstk(struct task_struct *task, unsigned long shstk_addr) task->thread_info.user_cfi_state.user_shdw_stk = shstk_addr; } +void set_shstk_status(struct task_struct *task, bool enable) +{ + if (!cpu_supports_shadow_stack()) + return; + + task->thread_info.user_cfi_state.ubcfi_en = enable ? 1 : 0; + + if (enable) + task->thread.envcfg |= ENVCFG_SSE; + else + task->thread.envcfg &= ~ENVCFG_SSE; + + csr_write(CSR_ENVCFG, task->thread.envcfg); +} + +void set_shstk_lock(struct task_struct *task) +{ + task->thread_info.user_cfi_state.ubcfi_locked = 1; +} + /* * If size is 0, then to be compatible with regular stack we want it to be as big as * regular stack. Else PAGE_ALIGN it and return back @@ -260,3 +290,83 @@ void shstk_release(struct task_struct *tsk) vm_munmap(base, size); set_shstk_base(tsk, 0, 0); } + +int arch_get_shadow_stack_status(struct task_struct *t, unsigned long __user *status) +{ + unsigned long bcfi_status = 0; + + if (!cpu_supports_shadow_stack()) + return -EINVAL; + + /* this means shadow stack is enabled on the task */ + bcfi_status |= (is_shstk_enabled(t) ? PR_SHADOW_STACK_ENABLE : 0); + + return copy_to_user(status, &bcfi_status, sizeof(bcfi_status)) ? -EFAULT : 0; +} + +int arch_set_shadow_stack_status(struct task_struct *t, unsigned long status) +{ + unsigned long size = 0, addr = 0; + bool enable_shstk = false; + + if (!cpu_supports_shadow_stack()) + return -EINVAL; + + /* Reject unknown flags */ + if (status & ~PR_SHADOW_STACK_SUPPORTED_STATUS_MASK) + return -EINVAL; + + /* bcfi status is locked and further can't be modified by user */ + if (is_shstk_locked(t)) + return -EINVAL; + + enable_shstk = status & PR_SHADOW_STACK_ENABLE; + /* Request is to enable shadow stack and shadow stack is not enabled already */ + if (enable_shstk && !is_shstk_enabled(t)) { + /* shadow stack was allocated and enable request again + * no need to support such usecase and return EINVAL. + */ + if (is_shstk_allocated(t)) + return -EINVAL; + + size = calc_shstk_size(0); + addr = allocate_shadow_stack(0, size, 0, false); + if (IS_ERR_VALUE(addr)) + return -ENOMEM; + set_shstk_base(t, addr, size); + set_active_shstk(t, addr + size); + } + + /* + * If a request to disable shadow stack happens, let's go ahead and release it + * Although, if CLONE_VFORKed child did this, then in that case we will end up + * not releasing the shadow stack (because it might be needed in parent). Although + * we will disable it for VFORKed child. And if VFORKed child tries to enable again + * then in that case, it'll get entirely new shadow stack because following condition + * are true + * - shadow stack was not enabled for vforked child + * - shadow stack base was anyways pointing to 0 + * This shouldn't be a big issue because we want parent to have availability of shadow + * stack whenever VFORKed child releases resources via exit or exec but at the same + * time we want VFORKed child to break away and establish new shadow stack if it desires + * + */ + if (!enable_shstk) + shstk_release(t); + + set_shstk_status(t, enable_shstk); + return 0; +} + +int arch_lock_shadow_stack_status(struct task_struct *task, + unsigned long arg) +{ + /* If shtstk not supported or not enabled on task, nothing to lock here */ + if (!cpu_supports_shadow_stack() || + !is_shstk_enabled(task) || arg != 0) + return -EINVAL; + + set_shstk_lock(task); + + return 0; +} -- 2.43.0