From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-dy1-f170.google.com (mail-dy1-f170.google.com [74.125.82.170]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id BEC9639795B for ; Fri, 16 Oct 2026 19:46:25 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=74.125.82.170 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1792179987; cv=none; b=qq+CbKYqODO+vtu51IKCuKOsaan33I84CUF5/cJVgcv4C9J1WkMWOzUClFG3OQiPCDUmPpF7dc73sdylxzQhJc6yGgnJTe0QkueIpdPASTB56AqSsEaHTieJBfx0oZ82D72Ya60RVyWBDjIlWeKxPhiaJ+L8JFwm8QBBMe5sU/8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1792179987; c=relaxed/simple; bh=UKHfm3hib73pa55eKddhtXLxTqC68GbL0KmbqqEd5N8=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=LU0QpMhtWyG/ivCeGbKXy5evpa07sQjYJbvjtDV1haY6SGORz/FMqn9fbC0BdHhHJ90hWbRdxauo43VHy3qeZ4IypVMH/utyElYVbZGX8yVaWLGxTVSLGAez2/Fh3MnsK+Em6NFCFo2YMFtaebvXB/id/QC8UnOfIQOoLJKzb0U= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=HxWzW2es; arc=none smtp.client-ip=74.125.82.170 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="HxWzW2es" Received: by mail-dy1-f170.google.com with SMTP id 5a478bee46e88-35ef6b49813so481037eec.0 for ; Fri, 16 Oct 2026 12:46:25 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1792179985; x=1792784785; darn=vger.kernel.org; h=content-transfer-encoding:content-type:mime-version:references :in-reply-to:message-id:date:subject:cc:to:from:from:to:cc:subject :date:message-id:reply-to:content-type; bh=mzEjDaJTDISex2ZPOiizRCuwngZ28JcDGHKte0m6HrM=; b=HxWzW2esgtZm1ryn5BNufXdKutdKZI3lAbTKQqmMFjJixbLB4IIr7lBpKPBgmJ/ceL SSzgzLnNdNqsYJZoy8qijie/5TC0csi0Ps2m8VtelH869ZGh0xLJ5cIHT+04Sek2TEU9 lxKa6LGhnVeADv/DNlZGEr4wBSgAPjxPbedffvhkb0spn+Ck0T0rVQV6OmvgKeA5uR/r GIQ8s97TEedxC2cE/9H12sJ1FdgWh9ckbJip4LxdVak6DL8Zo0+4ytvFjylgBYHcyLcV GKX13kq2swhqprDUmXDVS5vsy7AyXyjOkJJMOyjee5JgzEBWYogYQFHHH+r4Ds0wuu+/ NT7A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1792179985; x=1792784785; h=content-transfer-encoding:content-type:mime-version:references :in-reply-to:message-id:date:subject:cc:to:from:x-gm-gg :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to :content-type; bh=mzEjDaJTDISex2ZPOiizRCuwngZ28JcDGHKte0m6HrM=; b=IXT6hgZXmMKvPdybukVnxpS5GvrcIq99+vXvzeFXqf2Vva2BPl8upf8Eoxkhb5F0Ny XinO0ipmWw0JUXJAZ4GtYm7hc65Uq9NJK6FU+K69huVRPYHt3M5M88N5CsFgX+JFFxTD 87yIgj6fvBrzhDHbgzI90bp3Hiup+Wd3lxG2ZuIa6eMLJEcpnJH6+J9Js8Pk2vyVfA0K G/pRIIuVMP1PpsD5eJ8ClYeiCZCymabd3T+xuol0m1p6ErgxnevXHXoiPxeIlOh1e5Nq un345kUhR59JvEatYjum0rxgOS155j5ui15orWniZX3s/WL4eV5KCXurK1uS0hDzn47Z vFSQ== X-Gm-Message-State: AFq9FYI5BPRR3QaKExY7IgZCSDAW1RUyVsdonooTvn/R+6v9zBK/SAcv oUE6exIvW0dQe4HYCDtoiuNGtoVa0HGznLpJ3tegJdWDhGxNHcCOESXi X-Gm-Gg: AYBFou2uCijsQop8qfDyWBlmsmCfnNnHhVxFhIXPfWfSGQb/n+DfChuFMOF5dLL1j+c OCkv86eZSJobuEuuYhG6LLVanQwXUj7/vi+IR/0gQbjkzqI9FzMbxUId7m6JVFzX09tfNxfX8Bm DoWeOKUX9MTEaRhJXX6HVzmCxVi/d2WpkfNuYwgHX5zf/JCtgrTC/QQpHnbzvKo6Y3RR0G72yp+ TZhCXfc/aQNcU54c8JCqLWvtJAcWd73fgVl3Qw7xeI1by9A/tflrhot29zxUpMucbC5it34Sdz9 RA6k/fMM6jXnOJ0C61pmkJK3HejB2zoZOXTtXz59PE1SDs4l4aBKK7QnCXzKaTNnsjjbhYZ9dBK VS4z3RCLS7rHbwlNQcRoBB2K0MbQp38pj66FGKTmUEZrFgz5aWKbUlDro0N3IOpKo2cIVryH8Im U183QiJZKfWVH5fihSxZ/xHcKvjFdgjXSJumKI5UBSdKXsslaaZitpKo/jcpS6C9tmvJ+ckzA0w z0= X-Received: by 2002:a05:7022:f90e:b0:168:3243:c937 with SMTP id a92af1059eb24-185119e3cfamr1015727c88.16.1792179983649; Fri, 16 Oct 2026 12:46:23 -0700 (PDT) Received: from unix.. ([181.229.23.179]) by smtp.gmail.com with ESMTPSA id a92af1059eb24-1831b75be5esm11008321c88.16.2026.10.16.12.46.18 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 16 Oct 2026 12:46:22 -0700 (PDT) From: =?UTF-8?q?Iv=C3=A1n=20Ezequiel=20Rodriguez?= To: Catalin Marinas , Will Deacon , Paul Walmsley , Palmer Dabbelt , linux-arm-kernel@lists.infradead.org, linux-riscv@lists.infradead.org Cc: linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, Mark Rutland , Mark Brown , Deepak Gupta , Alexandre Ghiti , Albert Ou , Shuah Khan , Christian Brauner , James Morse , Yury Khrustalev , Thiago Jung Bauermann , Samuel Holland , Zong Li , Charlie Jenkins , Shaopeng Tan , Zishun Yi , "Peter Zijlstra (Intel)" , stable@vger.kernel.org Subject: [PATCH 2/4] riscv/shstk: release shadow stack on failed fork Date: Fri, 16 Oct 2026 16:46:01 -0300 Message-ID: <75e29a5db0166247c407bd51f184864b398a2ee6.1792179433.git.ivanrwcm25@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: References: 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: 8bit copy_thread() maps a shadow stack for a CLONE_VM child and can still return 0. A later copy_process() failure, including clone3() CLONE_PIDFD when put_user() fails, goes through bad_fork_cleanup_thread and exit_thread(). riscv did not select HAVE_EXIT_THREAD, so that free was a no-op. shstk_release() already documents this call; deactivate_mm() is the only path that actually reached it. Select HAVE_EXIT_THREAD and call shstk_release() from exit_thread(). The helper already refuses a different mm and a cleared base, so CLONE_VFORK, !CLONE_VM, and a second call after deactivate_mm() stay no-ops. Do not free when shstk_alloc_thread_stack() fails. That error returns from copy_thread() with the inherited parent base still in place, and copy_process() skips exit_thread() on that path. A kthread copies the caller's tracking via arch_dup_task_struct(). kernel_thread() uses CLONE_VM, so during a failed copy_process() the child still shares the caller's mm and shstk_release()'s mm check does not save us. Clear the inherited tracking as part of kthread setup. Fixes: fd44a4a85516 ("riscv/shstk: If needed allocate a new shadow stack on clone") Cc: stable@vger.kernel.org Cc: Deepak Gupta Assisted-by: LLM Signed-off-by: Iván Ezequiel Rodriguez --- arch/riscv/Kconfig | 1 + arch/riscv/kernel/process.c | 18 ++++++++++++++++++ 2 files changed, 19 insertions(+) diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig index 5874ca30f4f6..7635f8cb0397 100644 --- a/arch/riscv/Kconfig +++ b/arch/riscv/Kconfig @@ -169,6 +169,7 @@ config RISCV select HAVE_FUNCTION_GRAPH_FREGS select HAVE_FUNCTION_TRACER if HAVE_DYNAMIC_FTRACE select HAVE_EBPF_JIT if MMU + select HAVE_EXIT_THREAD select HAVE_GENERIC_TIF_BITS select HAVE_GUP_FAST if MMU select HAVE_FUNCTION_ARG_ACCESS_API diff --git a/arch/riscv/kernel/process.c b/arch/riscv/kernel/process.c index 7cc5a6a5c020..def1f520d9ef 100644 --- a/arch/riscv/kernel/process.c +++ b/arch/riscv/kernel/process.c @@ -12,6 +12,7 @@ #include #include #include +#include #include #include #include @@ -213,6 +214,16 @@ void arch_release_task_struct(struct task_struct *tsk) riscv_v_thread_free(tsk); } +void exit_thread(struct task_struct *tsk) +{ + /* + * shstk_release() documents this call for a failed CLONE_VM + * clone. copy_process() reaches it only after copy_thread() + * returns 0; deactivate_mm() does not run on that path. + */ + shstk_release(tsk); +} + int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src) { fstate_save(src, task_pt_regs(src)); @@ -261,6 +272,13 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args) p->thread.s[0] = (unsigned long)args->fn; p->thread.s[1] = (unsigned long)args->fn_arg; p->thread.ra = (unsigned long)ret_from_fork_kernel_asm; + /* + * kernel_thread() uses CLONE_VM, so a failed + * copy_process() still shares the caller's mm. + * Inherited tracking would then look like a child + * mapping to shstk_release(). + */ + set_shstk_base(p, 0, 0); } else { /* allocate new shadow stack if needed. In case of CLONE_VM we have to */ ssp = shstk_alloc_thread_stack(p, args); -- 2.43.0