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Thu, 22 May 2025 22:31:32 -0700 (PDT) From: Deepak Gupta Date: Thu, 22 May 2025 22:31:09 -0700 Subject: [PATCH v16 06/27] riscv/mm : ensure PROT_WRITE leads to VM_READ | VM_WRITE MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20250522-v5_user_cfi_series-v16-6-64f61a35eee7@rivosinc.com> References: <20250522-v5_user_cfi_series-v16-0-64f61a35eee7@rivosinc.com> In-Reply-To: <20250522-v5_user_cfi_series-v16-0-64f61a35eee7@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?= , Benno Lossin , Andreas Hindborg , Alice Ryhl , Trevor Gross 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 , Deepak Gupta X-Mailer: b4 0.13.0 X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 8CDBB120008 X-Stat-Signature: prfhoxpx9axreq3ohdnfwhd6u1it4wf3 X-Rspam-User: X-HE-Tag: 1747978304-48953 X-HE-Meta: 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 vwNvSjwf 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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: `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. Reviewed-by: Zong Li Reviewed-by: Alexandre Ghiti Signed-off-by: Arnd Bergmann Signed-off-by: Deepak Gupta --- arch/riscv/include/asm/mman.h | 25 +++++++++++++++++++++++++ arch/riscv/include/asm/pgtable.h | 1 + arch/riscv/kernel/sys_riscv.c | 10 ++++++++++ arch/riscv/mm/init.c | 2 +- 4 files changed, 37 insertions(+), 1 deletion(-) diff --git a/arch/riscv/include/asm/mman.h b/arch/riscv/include/asm/mman.h new file mode 100644 index 000000000000..392c9c2d2e78 --- /dev/null +++ b/arch/riscv/include/asm/mman.h @@ -0,0 +1,25 @@ +/* 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 428e48e5f57d..dba257cc4e2d 100644 --- a/arch/riscv/include/asm/pgtable.h +++ b/arch/riscv/include/asm/pgtable.h @@ -182,6 +182,7 @@ extern struct pt_alloc_ops pt_ops __meminitdata; #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 d77afe05578f..43a448bf254b 100644 --- a/arch/riscv/kernel/sys_riscv.c +++ b/arch/riscv/kernel/sys_riscv.c @@ -7,6 +7,7 @@ #include #include +#include static long riscv_sys_mmap(unsigned long addr, unsigned long len, unsigned long prot, unsigned long flags, @@ -16,6 +17,15 @@ static long riscv_sys_mmap(unsigned long addr, unsigned long len, if (unlikely(offset & (~PAGE_MASK >> page_shift_offset))) return -EINVAL; + /* + * If 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))) + 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 ab475ec6ca42..78b27164bf83 100644 --- a/arch/riscv/mm/init.c +++ b/arch/riscv/mm/init.c @@ -375,7 +375,7 @@ 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, -- 2.43.0