From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-io1-f52.google.com (mail-io1-f52.google.com [209.85.166.52]) (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 77F1A18A6A0 for ; Mon, 7 Oct 2024 08:17:59 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.166.52 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728289082; cv=none; b=LV12tG0vatLhYk8qGhc0WfCLA93r9VbiBAKxg7UQfXMgxEWNvIA9MNsQcNSjNkHbNoy1HsXtvPikY7seitNOSYwOd3eiv0pMVygP8HflEBziOQBlT37jJ5zw3c1MFdKC7+bMBvazszVoYsmuGMok5/DaktLDam0WD0ImEPndK2c= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728289082; c=relaxed/simple; bh=Nmph6WDs9Xq7iTOfvd0cLrjjvG2iMe2g5y57xwNvOkQ=; h=MIME-Version:References:In-Reply-To:From:Date:Message-ID:Subject: To:Cc:Content-Type; b=iovHP+lf9wxFfX23/2P7zxFhX1o7Ml7HUdK4v2stAnWeaDsRJob5I1L3ysdiaSAYOVEDsZ23ZmYLyRbAz3i9L49QpeMXqMI7GRlkeVBHWEyU186P1zHxHPg1EZJVVHTQX3GWqG3P0+RFkglR+PqNSDyH1Z8UtQYeo8IQNL07x1I= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=sifive.com; spf=pass smtp.mailfrom=sifive.com; dkim=pass (2048-bit key) header.d=sifive.com header.i=@sifive.com header.b=XSGIF6M2; arc=none smtp.client-ip=209.85.166.52 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=sifive.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=sifive.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=sifive.com header.i=@sifive.com header.b="XSGIF6M2" Received: by mail-io1-f52.google.com with SMTP id ca18e2360f4ac-82aa7c3b3dbso165465539f.2 for ; Mon, 07 Oct 2024 01:17:59 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sifive.com; s=google; t=1728289078; x=1728893878; darn=vger.kernel.org; h=content-transfer-encoding:cc:to:subject:message-id:date:from :in-reply-to:references:mime-version:from:to:cc:subject:date :message-id:reply-to; bh=vV5iKTZRSVTQUCoJBZzYZK+9ejJVraol8LawWsL5uGA=; b=XSGIF6M25Lbz0GpQpKB5rNdxaLqJ+91BffQhZawZ8hJ9WodEiehgVlQXcPY6vDjDNQ MaSj2qxb5wHrX6+Mj5hjS8e8uyp9uxDMZD8t5sUKfTc3wEHAgj7V4eqLfbYQI2HpNLTJ DgP3n27FA34JxTz0cOjNAnuUhLi4zMsBxejCPkqPxxgpVmE4FMeNb8rAGVRyHxSxkccQ N+Rafv+NKwXl0/lQPFPCz9ZhNznlCIsBqokEpvGnzlsO/WUeOTqQryd3X3r/Ad04er+4 c4R3XI15030EUJYbCHsX9sD2uQKpy5RHDfxRmo5mKyeO4UrSOHg3I+oDm+ZFFuLEp6hz Ax3A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1728289078; x=1728893878; h=content-transfer-encoding:cc:to:subject:message-id:date:from :in-reply-to:references:mime-version:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=vV5iKTZRSVTQUCoJBZzYZK+9ejJVraol8LawWsL5uGA=; b=sPkW1HNEOlU/hKEp84UdgWEIHcKdIFLsNFPShDtaMbFtZQVLVj37pd2lQOwZS/29wa 6Pfu42MVtL8JHapUqFLAW6qUNLmrFQp+vyenJetEkW3E9U1g/ES2+viZAVNHspoMOKpQ p4XtFEoQXnlpBUrIPK7l2McIqk+Ct42OjCQCrB5yQFCUUwaaV30V4L4acvR+W6AZkbXs yl6H3KI0E5oxqF6VMWc9OYekseNFRR+FZ6StUeI4Ck8kZwfrNeh8h3Wf4YKuYW9RMw78 Y7CDCXMFhNYCAjaKuhOHN8t7IUuKSGaHHpa5FCwIKC1cCA3gjE0ltgtEYqEFKuesuAZB LQyA== X-Forwarded-Encrypted: i=1; AJvYcCXPsfyys/FuS+hjOGx1XUIITbB38lf93kPdzCR63ZF3GU5r1UXcti5v8pGKVGhsBwC5xvxyS2bmQj/4@vger.kernel.org X-Gm-Message-State: AOJu0Yx51aI8tuY635Rsq9ebOmNdfgahErge30sOHb1J0epGZr5yPMZq h5FgKGaqkiZr5CjxHG3ZyN5cP+VFsp0LITCVTMC6jMNU5ToS08YuGwvgkd4PUBVja2qmevFiPkD x+3SrlgOhu2KzNkVC1v2d4REM1gUdeFOP0NVtew== X-Google-Smtp-Source: AGHT+IGbrFX2fkGwh4/hSUi/bswFsAwHoZTucK0BPSJDYS8wpDCXqS1WF3XKaDolR3S9yJug1dqVltHjNKSJeho3ET0= X-Received: by 2002:a05:6602:14c1:b0:806:31ee:132 with SMTP id ca18e2360f4ac-834f7ca6040mr1014345639f.4.1728289078482; Mon, 07 Oct 2024 01:17:58 -0700 (PDT) Precedence: bulk X-Mailing-List: devicetree@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 References: <20241001-v5_user_cfi_series-v1-0-3ba65b6e550f@rivosinc.com> <20241001-v5_user_cfi_series-v1-16-3ba65b6e550f@rivosinc.com> In-Reply-To: <20241001-v5_user_cfi_series-v1-16-3ba65b6e550f@rivosinc.com> From: Zong Li Date: Mon, 7 Oct 2024 16:17:47 +0800 Message-ID: Subject: Re: [PATCH 16/33] riscv/shstk: If needed allocate a new shadow stack on clone To: Deepak Gupta Cc: 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 , 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 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Wed, Oct 2, 2024 at 12:20=E2=80=AFAM Deepak Gupta w= rote: > > Userspace specifies CLONE_VM to share address space and spawn new thread. > `clone` allow userspace to specify a new stack for new thread. However > there is no way to specify new shadow stack base address without changing > API. This patch allocates a new shadow stack whenever CLONE_VM is given. > > In case of CLONE_VFORK, parent is suspended until child finishes and thus > can child use parent shadow stack. In case of !CLONE_VM, COW kicks in > because entire address space is copied from parent to child. > > `clone3` is extensible and can provide mechanisms using which shadow stac= k > as an input parameter can be provided. This is not settled yet and being > extensively discussed on mailing list. Once that's settled, this commit > will adapt to that. > > Signed-off-by: Deepak Gupta > --- > arch/riscv/include/asm/usercfi.h | 25 ++++++++ > arch/riscv/kernel/process.c | 11 +++- > arch/riscv/kernel/usercfi.c | 121 +++++++++++++++++++++++++++++++++= ++++++ > 3 files changed, 156 insertions(+), 1 deletion(-) > > diff --git a/arch/riscv/include/asm/usercfi.h b/arch/riscv/include/asm/us= ercfi.h > index 4fa201b4fc4e..719e28e043c8 100644 > --- a/arch/riscv/include/asm/usercfi.h > +++ b/arch/riscv/include/asm/usercfi.h > @@ -8,6 +8,9 @@ > #ifndef __ASSEMBLY__ > #include > > +struct task_struct; > +struct kernel_clone_args; > + > #ifdef CONFIG_RISCV_USER_CFI > struct cfi_status { > unsigned long ubcfi_en : 1; /* Enable for backward cfi. */ > @@ -17,6 +20,28 @@ struct cfi_status { > unsigned long shdw_stk_size; /* size of shadow stack */ > }; > > +unsigned long shstk_alloc_thread_stack(struct task_struct *tsk, > + const struct kern= el_clone_args *args); > +void shstk_release(struct task_struct *tsk); > +void set_shstk_base(struct task_struct *task, unsigned long shstk_addr, = unsigned long size); > +unsigned long get_shstk_base(struct task_struct *task, unsigned long *si= ze); > +void set_active_shstk(struct task_struct *task, unsigned long shstk_addr= ); > +bool is_shstk_enabled(struct task_struct *task); > + > +#else > + > +#define shstk_alloc_thread_stack(tsk, args) 0 > + > +#define shstk_release(tsk) > + > +#define get_shstk_base(task, size) 0 > + > +#define set_shstk_base(task, shstk_addr, size) > + > +#define set_active_shstk(task, shstk_addr) > + > +#define is_shstk_enabled(task) false > + > #endif /* CONFIG_RISCV_USER_CFI */ > > #endif /* __ASSEMBLY__ */ > diff --git a/arch/riscv/kernel/process.c b/arch/riscv/kernel/process.c > index 1f2574fb2edb..f6f58b1ed905 100644 > --- a/arch/riscv/kernel/process.c > +++ b/arch/riscv/kernel/process.c > @@ -28,6 +28,7 @@ > #include > #include > #include > +#include > > #if defined(CONFIG_STACKPROTECTOR) && !defined(CONFIG_STACKPROTECTOR_PER= _TASK) > #include > @@ -203,7 +204,7 @@ int arch_dup_task_struct(struct task_struct *dst, str= uct task_struct *src) > > void exit_thread(struct task_struct *tsk) > { > - > + shstk_release(tsk); > } > > int copy_thread(struct task_struct *p, const struct kernel_clone_args *a= rgs) > @@ -211,6 +212,7 @@ int copy_thread(struct task_struct *p, const struct k= ernel_clone_args *args) > unsigned long clone_flags =3D args->flags; > unsigned long usp =3D args->stack; > unsigned long tls =3D args->tls; > + unsigned long ssp =3D 0; > struct pt_regs *childregs =3D task_pt_regs(p); > > memset(&p->thread.s, 0, sizeof(p->thread.s)); > @@ -225,11 +227,18 @@ int copy_thread(struct task_struct *p, const struct= kernel_clone_args *args) > p->thread.s[0] =3D (unsigned long)args->fn; > p->thread.s[1] =3D (unsigned long)args->fn_arg; > } else { > + /* allocate new shadow stack if needed. In case of CLONE_= VM we have to */ > + ssp =3D shstk_alloc_thread_stack(p, args); > + if (IS_ERR_VALUE(ssp)) > + return PTR_ERR((void *)ssp); > + > *childregs =3D *(current_pt_regs()); > /* Turn off status.VS */ > riscv_v_vstate_off(childregs); > if (usp) /* User fork */ > childregs->sp =3D usp; > + /* if needed, set new ssp */ > + ssp ? set_active_shstk(p, ssp) : 0; > if (clone_flags & CLONE_SETTLS) > childregs->tp =3D tls; > childregs->a0 =3D 0; /* Return value of fork() */ > diff --git a/arch/riscv/kernel/usercfi.c b/arch/riscv/kernel/usercfi.c > index ce002eabbdc1..7a7f0b57b2d4 100644 > --- a/arch/riscv/kernel/usercfi.c > +++ b/arch/riscv/kernel/usercfi.c > @@ -19,6 +19,41 @@ > > #define SHSTK_ENTRY_SIZE sizeof(void *) > > +bool is_shstk_enabled(struct task_struct *task) > +{ > + return task->thread_info.user_cfi_state.ubcfi_en ? true : false; > +} > + > +void set_shstk_base(struct task_struct *task, unsigned long shstk_addr, = unsigned long size) > +{ > + task->thread_info.user_cfi_state.shdw_stk_base =3D shstk_addr; > + task->thread_info.user_cfi_state.shdw_stk_size =3D size; > +} > + > +unsigned long get_shstk_base(struct task_struct *task, unsigned long *si= ze) > +{ > + if (size) > + *size =3D task->thread_info.user_cfi_state.shdw_stk_size; > + return task->thread_info.user_cfi_state.shdw_stk_base; > +} > + > +void set_active_shstk(struct task_struct *task, unsigned long shstk_addr= ) > +{ > + task->thread_info.user_cfi_state.user_shdw_stk =3D shstk_addr; > +} > + > +/* > + * 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 > + */ > +static unsigned long calc_shstk_size(unsigned long size) > +{ > + if (size) > + return PAGE_ALIGN(size); > + > + return PAGE_ALIGN(min_t(unsigned long long, rlimit(RLIMIT_STACK),= SZ_4G)); > +} > + > /* > * Writes on shadow stack can either be `sspush` or `ssamoswap`. `sspush= ` can happen > * implicitly on current shadow stack pointed to by CSR_SSP. `ssamoswap`= takes pointer to > @@ -143,3 +178,89 @@ SYSCALL_DEFINE3(map_shadow_stack, unsigned long, add= r, unsigned long, size, unsi > > return allocate_shadow_stack(addr, aligned_size, size, set_tok); > } > + > +/* > + * This gets called during clone/clone3/fork. And is needed to allocate = a shadow stack for > + * cases where CLONE_VM is specified and thus a different stack is speci= fied by user. We > + * thus need a separate shadow stack too. How does separate shadow stack= is specified by > + * user is still being debated. Once that's settled, remove this part of= the comment. > + * This function simply returns 0 if shadow stack are not supported or i= f separate shadow > + * stack allocation is not needed (like in case of !CLONE_VM) > + */ > +unsigned long shstk_alloc_thread_stack(struct task_struct *tsk, > + const struct kernel_clone_args= *args) > +{ > + unsigned long addr, size; > + > + /* If shadow stack is not supported, return 0 */ > + if (!cpu_supports_shadow_stack()) > + return 0; > + > + /* > + * If shadow stack is not enabled on the new thread, skip any > + * switch to a new shadow stack. > + */ > + if (is_shstk_enabled(tsk)) Hi Deepak, Should it be '!' is_shstk_enabled(tsk)? > + return 0; > + > + /* > + * For CLONE_VFORK the child will share the parents shadow stack. > + * Set base =3D 0 and size =3D 0, this is special means to track = this state > + * so the freeing logic run for child knows to leave it alone. > + */ > + if (args->flags & CLONE_VFORK) { > + set_shstk_base(tsk, 0, 0); > + return 0; > + } > + > + /* > + * For !CLONE_VM the child will use a copy of the parents shadow > + * stack. > + */ > + if (!(args->flags & CLONE_VM)) > + return 0; > + > + /* > + * reaching here means, CLONE_VM was specified and thus a separat= e shadow > + * stack is needed for new cloned thread. Note: below allocation = is happening > + * using current mm. > + */ > + size =3D calc_shstk_size(args->stack_size); > + addr =3D allocate_shadow_stack(0, size, 0, false); > + if (IS_ERR_VALUE(addr)) > + return addr; > + > + set_shstk_base(tsk, addr, size); > + > + return addr + size; > +} > + > +void shstk_release(struct task_struct *tsk) > +{ > + unsigned long base =3D 0, size =3D 0; > + /* If shadow stack is not supported or not enabled, nothing to re= lease */ > + if (!cpu_supports_shadow_stack() || > + !is_shstk_enabled(tsk)) > + return; > + > + /* > + * When fork() with CLONE_VM fails, the child (tsk) already has a > + * shadow stack allocated, and exit_thread() calls this function = to > + * free it. In this case the parent (current) and the child shar= e > + * the same mm struct. Move forward only when they're same. > + */ > + if (!tsk->mm || tsk->mm !=3D current->mm) > + return; > + > + /* > + * We know shadow stack is enabled but if base is NULL, then > + * this task is not managing its own shadow stack (CLONE_VFORK). = So > + * skip freeing it. > + */ > + base =3D get_shstk_base(tsk, &size); > + if (!base) > + return; > + > + vm_munmap(base, size); > + set_shstk_base(tsk, 0, 0); > +} > > -- > 2.45.0 > > > _______________________________________________ > linux-riscv mailing list > linux-riscv@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-riscv