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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, Valentin Haudiquet , Deepak Gupta X-Mailer: b4 0.13.0 X-Developer-Signature: v=1; a=ed25519-sha256; t=1765473664; l=8736; i=debug@rivosinc.com; s=20251023; h=from:subject:message-id; bh=6nSDtLgjK0qpcJ8EF9aEV4Ih9Ks269sJQEfcddW1GFQ=; b=M81mvgYQzDXK53n+q1IjaOGOjSZXM2sWZi/EWsvFySes0hGCYzkWeI/ReAEmVvOJbRWXIjeWb TfkezakObS1At3A0OnW+8NKjWQo8UqcqrZQrxQnSWIixL5jm7+BRTvD 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: 199bz45g1syj9s1zj88qa5k5p5j6xqmf X-Rspamd-Queue-Id: 9DD1D4000A X-Rspamd-Server: rspam06 X-Rspam-User: X-HE-Tag: 1765473678-569672 X-HE-Meta: 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 aCDGnXWA 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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 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