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Fri, 10 May 2024 14:03:00 -0700 (PDT) Received: from ghost ([2601:647:5700:6860:629e:3f2:f321:6c]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-1ef0c13873esm36725165ad.266.2024.05.10.14.02.55 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 10 May 2024 14:03:00 -0700 (PDT) Date: Fri, 10 May 2024 14:02:54 -0700 From: Charlie Jenkins To: Deepak Gupta Cc: paul.walmsley@sifive.com, rick.p.edgecombe@intel.com, broonie@kernel.org, Szabolcs.Nagy@arm.com, kito.cheng@sifive.com, keescook@chromium.org, ajones@ventanamicro.com, conor.dooley@microchip.com, cleger@rivosinc.com, atishp@atishpatra.org, alex@ghiti.fr, bjorn@rivosinc.com, alexghiti@rivosinc.com, samuel.holland@sifive.com, conor@kernel.org, linux-doc@vger.kernel.org, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, devicetree@vger.kernel.org, linux-mm@kvack.org, linux-arch@vger.kernel.org, linux-kselftest@vger.kernel.org, corbet@lwn.net, palmer@dabbelt.com, aou@eecs.berkeley.edu, robh+dt@kernel.org, krzysztof.kozlowski+dt@linaro.org, oleg@redhat.com, akpm@linux-foundation.org, arnd@arndb.de, ebiederm@xmission.com, Liam.Howlett@oracle.com, vbabka@suse.cz, lstoakes@gmail.com, shuah@kernel.org, brauner@kernel.org, andy.chiu@sifive.com, jerry.shih@sifive.com, hankuan.chen@sifive.com, greentime.hu@sifive.com, evan@rivosinc.com, xiao.w.wang@intel.com, apatel@ventanamicro.com, mchitale@ventanamicro.com, dbarboza@ventanamicro.com, sameo@rivosinc.com, shikemeng@huaweicloud.com, willy@infradead.org, vincent.chen@sifive.com, guoren@kernel.org, samitolvanen@google.com, songshuaishuai@tinylab.org, gerg@kernel.org, heiko@sntech.de, bhe@redhat.com, jeeheng.sia@starfivetech.com, cyy@cyyself.name, maskray@google.com, ancientmodern4@gmail.com, mathis.salmen@matsal.de, cuiyunhui@bytedance.com, bgray@linux.ibm.com, mpe@ellerman.id.au, baruch@tkos.co.il, alx@kernel.org, david@redhat.com, catalin.marinas@arm.com, revest@chromium.org, josh@joshtriplett.org, shr@devkernel.io, deller@gmx.de, omosnace@redhat.com, ojeda@kernel.org, jhubbard@nvidia.com Subject: Re: [PATCH v3 10/29] riscv/mm : ensure PROT_WRITE leads to VM_READ | VM_WRITE Message-ID: References: <20240403234054.2020347-1-debug@rivosinc.com> <20240403234054.2020347-11-debug@rivosinc.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20240403234054.2020347-11-debug@rivosinc.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240510_140301_872495_AA772047 X-CRM114-Status: GOOD ( 30.33 ) X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-riscv" Errors-To: linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org On Wed, Apr 03, 2024 at 04:34:58PM -0700, Deepak Gupta wrote: > `arch_calc_vm_prot_bits` is implemented on risc-v to return VM_READ | > VM_WRITE if PROT_WRITE is specified. Similarly `riscv_sys_mmap` is > updated to convert all incoming PROT_WRITE to (PROT_WRITE | PROT_READ). > This is to make sure that any existing apps using PROT_WRITE still work. > > Earlier `protection_map[VM_WRITE]` used to pick read-write PTE encodings. > Now `protection_map[VM_WRITE]` will always pick PAGE_SHADOWSTACK PTE > encodings for shadow stack. Above changes ensure that existing apps > continue to work because underneath kernel will be picking > `protection_map[VM_WRITE|VM_READ]` PTE encodings. > > Signed-off-by: Deepak Gupta > --- > arch/riscv/include/asm/mman.h | 24 ++++++++++++++++++++++++ > arch/riscv/include/asm/pgtable.h | 1 + > arch/riscv/kernel/sys_riscv.c | 11 +++++++++++ > arch/riscv/mm/init.c | 2 +- > mm/mmap.c | 1 + > 5 files changed, 38 insertions(+), 1 deletion(-) > create mode 100644 arch/riscv/include/asm/mman.h > > diff --git a/arch/riscv/include/asm/mman.h b/arch/riscv/include/asm/mman.h > new file mode 100644 > index 000000000000..ef9fedf32546 > --- /dev/null > +++ b/arch/riscv/include/asm/mman.h > @@ -0,0 +1,24 @@ > +/* SPDX-License-Identifier: GPL-2.0 */ > +#ifndef __ASM_MMAN_H__ > +#define __ASM_MMAN_H__ > + > +#include > +#include > +#include > + > +static inline unsigned long arch_calc_vm_prot_bits(unsigned long prot, > + unsigned long pkey __always_unused) > +{ > + unsigned long ret = 0; > + > + /* > + * If PROT_WRITE was specified, force it to VM_READ | VM_WRITE. > + * Only VM_WRITE means shadow stack. > + */ > + if (prot & PROT_WRITE) > + ret = (VM_READ | VM_WRITE); > + return ret; > +} > +#define arch_calc_vm_prot_bits(prot, pkey) arch_calc_vm_prot_bits(prot, pkey) > + > +#endif /* ! __ASM_MMAN_H__ */ > diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h > index 6066822e7396..4d5983bc6766 100644 > --- a/arch/riscv/include/asm/pgtable.h > +++ b/arch/riscv/include/asm/pgtable.h > @@ -184,6 +184,7 @@ extern struct pt_alloc_ops pt_ops __initdata; > #define PAGE_READ_EXEC __pgprot(_PAGE_BASE | _PAGE_READ | _PAGE_EXEC) > #define PAGE_WRITE_EXEC __pgprot(_PAGE_BASE | _PAGE_READ | \ > _PAGE_EXEC | _PAGE_WRITE) > +#define PAGE_SHADOWSTACK __pgprot(_PAGE_BASE | _PAGE_WRITE) > > #define PAGE_COPY PAGE_READ > #define PAGE_COPY_EXEC PAGE_READ_EXEC > diff --git a/arch/riscv/kernel/sys_riscv.c b/arch/riscv/kernel/sys_riscv.c > index f1c1416a9f1e..846c36b1b3d5 100644 > --- a/arch/riscv/kernel/sys_riscv.c > +++ b/arch/riscv/kernel/sys_riscv.c > @@ -8,6 +8,8 @@ > #include > #include > #include > +#include > +#include > > static long riscv_sys_mmap(unsigned long addr, unsigned long len, > unsigned long prot, unsigned long flags, > @@ -17,6 +19,15 @@ static long riscv_sys_mmap(unsigned long addr, unsigned long len, > if (unlikely(offset & (~PAGE_MASK >> page_shift_offset))) > return -EINVAL; > > + /* > + * If only PROT_WRITE is specified then extend that to PROT_READ > + * protection_map[VM_WRITE] is now going to select shadow stack encodings. > + * So specifying PROT_WRITE actually should select protection_map [VM_WRITE | VM_READ] > + * If user wants to create shadow stack then they should use `map_shadow_stack` syscall. > + */ > + if (unlikely((prot & PROT_WRITE) && !(prot & PROT_READ))) The comments says that this should extend to PROT_READ if only PROT_WRITE is specified. This condition instead is checking if PROT_WRITE is selected but PROT_READ is not. If prot is (VM_EXEC | VM_WRITE) then it would be extended to (VM_EXEC | VM_WRITE | VM_READ). This will not currently cause any issues because these both map to the same value in the protection_map PAGE_COPY_EXEC, however this seems to be not the intention of this change. prot == PROT_WRITE better suits the condition explained in the comment. > + prot |= PROT_READ; > + > return ksys_mmap_pgoff(addr, len, prot, flags, fd, > offset >> (PAGE_SHIFT - page_shift_offset)); > } > diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c > index fa34cf55037b..98e5ece4052a 100644 > --- a/arch/riscv/mm/init.c > +++ b/arch/riscv/mm/init.c > @@ -299,7 +299,7 @@ pgd_t early_pg_dir[PTRS_PER_PGD] __initdata __aligned(PAGE_SIZE); > static const pgprot_t protection_map[16] = { > [VM_NONE] = PAGE_NONE, > [VM_READ] = PAGE_READ, > - [VM_WRITE] = PAGE_COPY, > + [VM_WRITE] = PAGE_SHADOWSTACK, > [VM_WRITE | VM_READ] = PAGE_COPY, > [VM_EXEC] = PAGE_EXEC, > [VM_EXEC | VM_READ] = PAGE_READ_EXEC, > diff --git a/mm/mmap.c b/mm/mmap.c > index d89770eaab6b..57a974f49b00 100644 > --- a/mm/mmap.c > +++ b/mm/mmap.c > @@ -47,6 +47,7 @@ > #include > #include > #include > +#include It doesn't seem like this is necessary for this patch. - Charlie > > #include > #include > -- > 2.43.2 > _______________________________________________ linux-riscv mailing list linux-riscv@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-riscv