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Tue, 04 Feb 2025 17:22:05 -0800 (PST) From: Deepak Gupta Date: Tue, 04 Feb 2025 17:21:53 -0800 Subject: [PATCH v9 06/26] riscv/mm : ensure PROT_WRITE leads to VM_READ | VM_WRITE MIME-Version: 1.0 Message-Id: <20250204-v5_user_cfi_series-v9-6-b37a49c5205c@rivosinc.com> References: <20250204-v5_user_cfi_series-v9-0-b37a49c5205c@rivosinc.com> In-Reply-To: <20250204-v5_user_cfi_series-v9-0-b37a49c5205c@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 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, Deepak Gupta X-Mailer: b4 0.14.0 X-Rspam-User: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: B68CE140004 X-Stat-Signature: 4hyzcg88hwpuy4kh1s4g77e54cftd1i6 X-HE-Tag: 1738718526-315043 X-HE-Meta: U2FsdGVkX1+NlVO3pKO9Y6Rn/3pqhsTR05eQmjoUyR7t4COepCaK7vHajz96oVC3UTPTZkdb/RJVNHNUXF52gpcNxz2hQ/B7O3fPGMRuwFYzHdGi5zw4dxSJ938kB7HDQXbNXkpjlpIDv+Ve1KPChyI1WILMS+ceUo5zFDlBUDH2WlE9466k1WyJII5oQFM0TPF16Ktkn2zw6vWox4HmqK/ulzf8ZxrEVY0ZaLr/d6UVivm4N8/6sbnCbYHtvZp/ekZXS06vv+6RADSK5uoaQtDiY7RBMzKytszIPRSOywRCwnScngPj4gYq5wNtD0Ly5APvKeXWy5wQ3+iPTgrJGJGBBfCBWaRCxodpuGNT2oX+QVXNVlJ1Aj+2jZRkB4ySktberyekB4WYhdtDhjBgz2KGxps9Omm9BZupAk1p4LtgQ7FuvryVQoi/BFCSfDPlDlBrie/NgolU5RqvP+9HuCSINHUcQS8CyFXOlomlKBZNtL80CZc25KqvR4jPb+2MPFdshP8SbbgbpClYaOTSj3tYCRZYJgrBrc1ihLYc8kSuElGrc1hIcea3+fNX4TplRQ3yQQ5gu3G3SCESwbANJPCQb4Lbr07j5/4A8rUWZTnuA1d/W0ytNFu4UUOf1LPApps7ObjXAHdDiJbJIJI1CiIVc8hE1uMfgcmBQHN7UsXMKPhPl7kS1IkdlUGoYpz3zTp9M1byNLYobja163YmpxAyb08CCceuFaaMqRE77CN1fuRxh2GOTD3rq+uBWK5hpntxthgkYGTd4a/K/VLcYsQuX8WoSbdfuOkYQ7AtYZflzwuIXir2QVmX/WI5EZTSKGhcLFm/yjZP625oggEp9RSov31Rc0K2DFImQeTaV5+k/EiKgad6kcnLGoNLbEaXq+b/p0XPlMajKkT5+IZaVze1LgCuSJ29Ga+Pkr96KOb8+2cf3OksYcPnB7oLmhmGhyICdjdjMQAFGqEHwfD d5c3/hrY 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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. 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 050fdc49b5ad..8c528cd7347a 100644 --- a/arch/riscv/include/asm/pgtable.h +++ b/arch/riscv/include/asm/pgtable.h @@ -178,6 +178,7 @@ 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 15b2eda4c364..9d6661638d0b 100644 --- a/arch/riscv/mm/init.c +++ b/arch/riscv/mm/init.c @@ -342,7 +342,7 @@ 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,