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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?= , Andreas Hindborg , Alice Ryhl , Trevor Gross , Benno Lossin 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, Paul Walmsley , Valentin Haudiquet , Deepak Gupta X-Mailer: b4 0.13.0 X-Developer-Signature: v=1; a=ed25519-sha256; t=1764960107; l=8783; i=debug@rivosinc.com; s=20251023; h=from:subject:message-id; bh=P5a3jHmT9CXsbMJac5CZkfX7UpuDBHAi+lZBTbV3fm8=; b=TQ4Z8rKEF/f4oE79cacHWnnXQoemEW1KOPVE1Jpq/ehYwBch3q9pNb1olDW7NhmJV+6vhbson VyLQjY0ur3mAF54VI1e6jUs0z7k6i80c7G3LdwcWydCLV31e/j1daV0 X-Developer-Key: i=debug@rivosinc.com; a=ed25519; pk=O37GQv1thBhZToXyQKdecPDhtWVbEDRQ0RIndijvpjk= X-Endpoint-Received: by B4 Relay for debug@rivosinc.com/20251023 with auth_id=553 X-Original-From: Deepak Gupta Reply-To: debug@rivosinc.com X-Stat-Signature: kymwhi73716nc8h535ekfp5c4pwrhmeo X-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 7C85414001A X-HE-Tag: 1764960122-554431 X-HE-Meta: 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 HDNsNIK4 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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: From: Deepak Gupta This commit adds a kernel command line option to disable part or all of user cfi. User backward cfi and forward cfi can be controlled independently. Kernel command line parameter "riscv_nousercfi" can take the following values: - "all" : Disable forward and backward cfi both. - "bcfi" : Disable backward cfi. - "fcfi" : Disable forward cfi Signed-off-by: Paul Walmsley Tested-by: Valentin Haudiquet Signed-off-by: Deepak Gupta --- Documentation/admin-guide/kernel-parameters.txt | 8 ++++ arch/riscv/include/asm/usercfi.h | 9 ++++ arch/riscv/kernel/cpufeature.c | 7 ++- arch/riscv/kernel/usercfi.c | 59 ++++++++++++++++++++----- 4 files changed, 70 insertions(+), 13 deletions(-) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 6c42061ca20e..a72bf9fc6f06 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -6453,6 +6453,14 @@ replacement properties are not found. See the Kconfig entry for RISCV_ISA_FALLBACK. + riscv_nousercfi= + all Disable user cfi ABI to userspace even if cpu extensions + are available. + bcfi Disable user backward cfi ABI to userspace even if + shadow stack extension is available. + fcfi Disable user forward cfi ABI to userspace even if landing + pad extension is available. + ro [KNL] Mount root device read-only on boot rodata= [KNL,EARLY] diff --git a/arch/riscv/include/asm/usercfi.h b/arch/riscv/include/asm/usercfi.h index ec4b8a53eb74..f7fa9d602aae 100644 --- a/arch/riscv/include/asm/usercfi.h +++ b/arch/riscv/include/asm/usercfi.h @@ -5,6 +5,10 @@ #ifndef _ASM_RISCV_USERCFI_H #define _ASM_RISCV_USERCFI_H +#define CMDLINE_DISABLE_RISCV_USERCFI_FCFI 1 +#define CMDLINE_DISABLE_RISCV_USERCFI_BCFI 2 +#define CMDLINE_DISABLE_RISCV_USERCFI 3 + #ifndef __ASSEMBLER__ #include #include @@ -12,8 +16,10 @@ struct task_struct; struct kernel_clone_args; +extern unsigned long riscv_nousercfi; #ifdef CONFIG_RISCV_USER_CFI + struct cfi_state { unsigned long ubcfi_en : 1; /* Enable for backward cfi. */ unsigned long ubcfi_locked : 1; @@ -83,6 +89,9 @@ void set_indir_lp_lock(struct task_struct *task); #endif /* CONFIG_RISCV_USER_CFI */ +bool is_user_shstk_enabled(void); +bool is_user_lpad_enabled(void); + #endif /* __ASSEMBLER__ */ #endif /* _ASM_RISCV_USERCFI_H */ diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c index 17b9e77bafc3..32ad463545fa 100644 --- a/arch/riscv/kernel/cpufeature.c +++ b/arch/riscv/kernel/cpufeature.c @@ -28,6 +28,7 @@ #include #include #include +#include #define NUM_ALPHA_EXTS ('z' - 'a' + 1) @@ -277,7 +278,8 @@ static int riscv_ext_svadu_validate(const struct riscv_isa_ext_data *data, static int riscv_cfilp_validate(const struct riscv_isa_ext_data *data, const unsigned long *isa_bitmap) { - if (!IS_ENABLED(CONFIG_RISCV_USER_CFI)) + if (!IS_ENABLED(CONFIG_RISCV_USER_CFI) || + (riscv_nousercfi & CMDLINE_DISABLE_RISCV_USERCFI_FCFI)) return -EINVAL; return 0; @@ -286,7 +288,8 @@ static int riscv_cfilp_validate(const struct riscv_isa_ext_data *data, static int riscv_cfiss_validate(const struct riscv_isa_ext_data *data, const unsigned long *isa_bitmap) { - if (!IS_ENABLED(CONFIG_RISCV_USER_CFI)) + if (!IS_ENABLED(CONFIG_RISCV_USER_CFI) || + (riscv_nousercfi & CMDLINE_DISABLE_RISCV_USERCFI_BCFI)) return -EINVAL; return 0; diff --git a/arch/riscv/kernel/usercfi.c b/arch/riscv/kernel/usercfi.c index 7f01befabd11..27b36034ea85 100644 --- a/arch/riscv/kernel/usercfi.c +++ b/arch/riscv/kernel/usercfi.c @@ -17,6 +17,8 @@ #include #include +unsigned long riscv_nousercfi; + #define SHSTK_ENTRY_SIZE sizeof(void *) bool is_shstk_enabled(struct task_struct *task) @@ -59,7 +61,7 @@ unsigned long get_active_shstk(struct task_struct *task) void set_shstk_status(struct task_struct *task, bool enable) { - if (!cpu_supports_shadow_stack()) + if (!is_user_shstk_enabled()) return; task->thread_info.user_cfi_state.ubcfi_en = enable ? 1 : 0; @@ -89,7 +91,7 @@ bool is_indir_lp_locked(struct task_struct *task) void set_indir_lp_status(struct task_struct *task, bool enable) { - if (!cpu_supports_indirect_br_lp_instr()) + if (!is_user_lpad_enabled()) return; task->thread_info.user_cfi_state.ufcfi_en = enable ? 1 : 0; @@ -259,7 +261,7 @@ SYSCALL_DEFINE3(map_shadow_stack, unsigned long, addr, unsigned long, size, unsi bool set_tok = flags & SHADOW_STACK_SET_TOKEN; unsigned long aligned_size = 0; - if (!cpu_supports_shadow_stack()) + if (!is_user_shstk_enabled()) return -EOPNOTSUPP; /* Anything other than set token should result in invalid param */ @@ -306,7 +308,7 @@ unsigned long shstk_alloc_thread_stack(struct task_struct *tsk, unsigned long addr, size; /* If shadow stack is not supported, return 0 */ - if (!cpu_supports_shadow_stack()) + if (!is_user_shstk_enabled()) return 0; /* @@ -352,7 +354,7 @@ void shstk_release(struct task_struct *tsk) { unsigned long base = 0, size = 0; /* If shadow stack is not supported or not enabled, nothing to release */ - if (!cpu_supports_shadow_stack() || !is_shstk_enabled(tsk)) + if (!is_user_shstk_enabled() || !is_shstk_enabled(tsk)) return; /* @@ -381,7 +383,7 @@ int arch_get_shadow_stack_status(struct task_struct *t, unsigned long __user *st { unsigned long bcfi_status = 0; - if (!cpu_supports_shadow_stack()) + if (!is_user_shstk_enabled()) return -EINVAL; /* this means shadow stack is enabled on the task */ @@ -395,7 +397,7 @@ int arch_set_shadow_stack_status(struct task_struct *t, unsigned long status) unsigned long size = 0, addr = 0; bool enable_shstk = false; - if (!cpu_supports_shadow_stack()) + if (!is_user_shstk_enabled()) return -EINVAL; /* Reject unknown flags */ @@ -448,7 +450,7 @@ int arch_lock_shadow_stack_status(struct task_struct *task, unsigned long arg) { /* If shtstk not supported or not enabled on task, nothing to lock here */ - if (!cpu_supports_shadow_stack() || + if (!is_user_shstk_enabled() || !is_shstk_enabled(task) || arg != 0) return -EINVAL; @@ -461,7 +463,7 @@ int arch_get_indir_br_lp_status(struct task_struct *t, unsigned long __user *sta { unsigned long fcfi_status = 0; - if (!cpu_supports_indirect_br_lp_instr()) + if (!is_user_lpad_enabled()) return -EINVAL; /* indirect branch tracking is enabled on the task or not */ @@ -474,7 +476,7 @@ int arch_set_indir_br_lp_status(struct task_struct *t, unsigned long status) { bool enable_indir_lp = false; - if (!cpu_supports_indirect_br_lp_instr()) + if (!is_user_lpad_enabled()) return -EINVAL; /* indirect branch tracking is locked and further can't be modified by user */ @@ -498,7 +500,7 @@ int arch_lock_indir_br_lp_status(struct task_struct *task, * If indirect branch tracking is not supported or not enabled on task, * nothing to lock here */ - if (!cpu_supports_indirect_br_lp_instr() || + if (!is_user_lpad_enabled() || !is_indir_lp_enabled(task) || arg != 0) return -EINVAL; @@ -506,3 +508,38 @@ int arch_lock_indir_br_lp_status(struct task_struct *task, return 0; } + +bool is_user_shstk_enabled(void) +{ + return (cpu_supports_shadow_stack() && + !(riscv_nousercfi & CMDLINE_DISABLE_RISCV_USERCFI_BCFI)); +} + +bool is_user_lpad_enabled(void) +{ + return (cpu_supports_indirect_br_lp_instr() && + !(riscv_nousercfi & CMDLINE_DISABLE_RISCV_USERCFI_FCFI)); +} + +static int __init setup_global_riscv_enable(char *str) +{ + if (strcmp(str, "all") == 0) + riscv_nousercfi = CMDLINE_DISABLE_RISCV_USERCFI; + + if (strcmp(str, "fcfi") == 0) + riscv_nousercfi |= CMDLINE_DISABLE_RISCV_USERCFI_FCFI; + + if (strcmp(str, "bcfi") == 0) + riscv_nousercfi |= CMDLINE_DISABLE_RISCV_USERCFI_BCFI; + + if (riscv_nousercfi) + pr_info("riscv user cfi disabled via cmdline " + "shadow stack status : %s, landing pad status : %s\n", + (riscv_nousercfi & CMDLINE_DISABLE_RISCV_USERCFI_BCFI) ? "disabled" : + "enabled", (riscv_nousercfi & CMDLINE_DISABLE_RISCV_USERCFI_FCFI) ? + "disabled" : "enabled"); + + return 1; +} + +__setup("riscv_nousercfi=", setup_global_riscv_enable); -- 2.43.0