From c0160dffe9a788ae0342e04af710628a68278043 Mon Sep 17 00:00:00 2001 From: Zong Li Date: Sun, 22 Mar 2026 23:56:40 -0700 Subject: [PATCH] riscv: cif: clear CFI lock status in start_thread When libc locks the CFI status through the following prctl: - PR_LOCK_SHADOW_STACK_STATUS - PR_LOCK_INDIR_BR_LP_STATUS A newly execd address space will inherit the lock status if it does not clear the lock bits. Since the lock bits remain set, libc will later fail to enable the landing pad and shadow stack. Signed-off-by: Zong Li Signed-off-by: Linux RISC-V bot --- arch/riscv/include/asm/usercfi.h | 8 ++++---- arch/riscv/kernel/process.c | 2 ++ arch/riscv/kernel/usercfi.c | 12 ++++++------ 3 files changed, 12 insertions(+), 10 deletions(-) diff --git a/arch/riscv/include/asm/usercfi.h b/arch/riscv/include/asm/usercfi.h index 7495baae1e3c2a..f56966edbf5c62 100644 --- a/arch/riscv/include/asm/usercfi.h +++ b/arch/riscv/include/asm/usercfi.h @@ -39,7 +39,7 @@ void set_active_shstk(struct task_struct *task, unsigned long shstk_addr); bool is_shstk_enabled(struct task_struct *task); bool is_shstk_locked(struct task_struct *task); bool is_shstk_allocated(struct task_struct *task); -void set_shstk_lock(struct task_struct *task); +void set_shstk_lock(struct task_struct *task, bool lock); void set_shstk_status(struct task_struct *task, bool enable); unsigned long get_active_shstk(struct task_struct *task); int restore_user_shstk(struct task_struct *tsk, unsigned long shstk_ptr); @@ -47,7 +47,7 @@ int save_user_shstk(struct task_struct *tsk, unsigned long *saved_shstk_ptr); bool is_indir_lp_enabled(struct task_struct *task); bool is_indir_lp_locked(struct task_struct *task); void set_indir_lp_status(struct task_struct *task, bool enable); -void set_indir_lp_lock(struct task_struct *task); +void set_indir_lp_lock(struct task_struct *task, bool lock); #define PR_SHADOW_STACK_SUPPORTED_STATUS_MASK (PR_SHADOW_STACK_ENABLE) @@ -69,7 +69,7 @@ void set_indir_lp_lock(struct task_struct *task); #define is_shstk_allocated(task) false -#define set_shstk_lock(task) do {} while (0) +#define set_shstk_lock(task, lock) do {} while (0) #define set_shstk_status(task, enable) do {} while (0) @@ -79,7 +79,7 @@ void set_indir_lp_lock(struct task_struct *task); #define set_indir_lp_status(task, enable) do {} while (0) -#define set_indir_lp_lock(task) do {} while (0) +#define set_indir_lp_lock(task, lock) do {} while (0) #define restore_user_shstk(tsk, shstk_ptr) -EINVAL diff --git a/arch/riscv/kernel/process.c b/arch/riscv/kernel/process.c index aacb23978f9313..596662de82e0e7 100644 --- a/arch/riscv/kernel/process.c +++ b/arch/riscv/kernel/process.c @@ -163,11 +163,13 @@ void start_thread(struct pt_regs *regs, unsigned long pc, set_shstk_status(current, false); set_shstk_base(current, 0, 0); set_active_shstk(current, 0); + set_shstk_lock(current, false); /* * disable indirect branch tracking on exec. * libc will enable it later via prctl. */ set_indir_lp_status(current, false); + set_indir_lp_lock(current, false); #ifdef CONFIG_64BIT regs->status &= ~SR_UXL; diff --git a/arch/riscv/kernel/usercfi.c b/arch/riscv/kernel/usercfi.c index 1adba746f164e5..9052171c1a8cc4 100644 --- a/arch/riscv/kernel/usercfi.c +++ b/arch/riscv/kernel/usercfi.c @@ -74,9 +74,9 @@ void set_shstk_status(struct task_struct *task, bool enable) csr_write(CSR_ENVCFG, task->thread.envcfg); } -void set_shstk_lock(struct task_struct *task) +void set_shstk_lock(struct task_struct *task, bool lock) { - task->thread_info.user_cfi_state.ubcfi_locked = 1; + task->thread_info.user_cfi_state.ubcfi_locked = lock; } bool is_indir_lp_enabled(struct task_struct *task) @@ -104,9 +104,9 @@ void set_indir_lp_status(struct task_struct *task, bool enable) csr_write(CSR_ENVCFG, task->thread.envcfg); } -void set_indir_lp_lock(struct task_struct *task) +void set_indir_lp_lock(struct task_struct *task, bool lock) { - task->thread_info.user_cfi_state.ufcfi_locked = 1; + task->thread_info.user_cfi_state.ufcfi_locked = lock; } /* * If size is 0, then to be compatible with regular stack we want it to be as big as @@ -452,7 +452,7 @@ int arch_lock_shadow_stack_status(struct task_struct *task, !is_shstk_enabled(task) || arg != 0) return -EINVAL; - set_shstk_lock(task); + set_shstk_lock(task, true); return 0; } @@ -502,7 +502,7 @@ int arch_lock_indir_br_lp_status(struct task_struct *task, !is_indir_lp_enabled(task) || arg != 0) return -EINVAL; - set_indir_lp_lock(task); + set_indir_lp_lock(task, true); return 0; }