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riscv: cfi: clear CFI lock status in start_thread()

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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 <zong.li@sifive.com>
Link: https://patch.msgid.link/20260323065640.4045713-1-zong.li@sifive.com
[pjw@kernel.org: ensure we unlock before changing state; cleaned up subject line]
Signed-off-by: Paul Walmsley <pjw@kernel.org>
This commit is contained in:
Zong Li
2026-04-04 18:40:58 -06:00
committed by Paul Walmsley
parent a621d9cdc8
commit a6ede084c4
3 changed files with 12 additions and 10 deletions
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12
arch/riscv/kernel/usercfi.c
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@@ -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;
}