On Tue, Jul 07, 2026 at 09:06:40PM +0200, Thomas Gleixner wrote:
> From: Jinjie Ruan <[email protected]>
>
> The return value of __secure_computing() currently uses 0 to indicate
> that a system call should be allowed, and -1 to indicate that it should
> be blocked/killed. This 0/-1 pattern is non-intuitive for a security
> check function and makes the control flow at the call sites less readable.
>
> Furthermore, any potential future changes to these return values would
> require a high-risk, error-prone audit of all its users across different
> architectures.
>
> Sanitize this logic by converting the return type of __secure_computing()
> to a proper boolean, where 'true' explicitly means 'allow' and 'false'
> means 'fail/deny'.
>
> Update all the two dozen or so call sites across the tree to align with
> this new boolean semantic. No functional changes are intended, as the
> callers still return -1 to the lower-level assembly entry code upon
> seccomp denial.
>
> Rename the function to __seccomp_permit_syscall() so that the purpose is
> entirely clear.
>
> [ tglx: Rename the function ]
>
> Suggested-by: Thomas Gleixner <[email protected]>
> Suggested-by: Mark Rutland <[email protected]>
> Signed-off-by: Jinjie Ruan <[email protected]>
> Signed-off-by: Thomas Gleixner <[email protected]>
> Cc: Kees Cook <[email protected]>
> Cc: Andy Lutomirski <[email protected]>
> Cc: Oleg Nesterov <[email protected]>
> Cc: Richard Henderson <[email protected]>
> Cc: Russell King <[email protected]>
> Cc: Catalin Marinas <[email protected]>
> Cc: Guo Ren <[email protected]>
> Cc: Geert Uytterhoeven <[email protected]>
> Cc: Thomas Bogendoerfer <[email protected]>
> Cc: Helge Deller <[email protected]>
> Cc: Yoshinori Sato <[email protected]>
> Cc: Richard Weinberger <[email protected]>
> Cc: Chris Zankel <[email protected]>
> Cc: [email protected]
> Cc: [email protected]
> Cc: [email protected]
> Cc: [email protected]
> Cc: [email protected]
> Cc: [email protected]
> Cc: [email protected]
> Cc: [email protected]
> ---
> arch/alpha/kernel/ptrace.c | 2 -
> arch/arm/kernel/ptrace.c | 2 -
> arch/arm64/kernel/ptrace.c | 2 -
> arch/csky/kernel/ptrace.c | 2 -
> arch/m68k/kernel/ptrace.c | 2 -
> arch/mips/kernel/ptrace.c | 2 -
> arch/parisc/kernel/ptrace.c | 2 -
> arch/sh/kernel/ptrace_32.c | 2 -
> arch/um/kernel/skas/syscall.c | 2 -
> arch/x86/entry/vsyscall/vsyscall_64.c | 14 ++++++-------
> arch/xtensa/kernel/ptrace.c | 3 --
> include/linux/entry-common.h | 9 +++-----
> include/linux/seccomp.h | 12 +++++------
> kernel/seccomp.c | 35
> +++++++++++++++++-----------------
> 14 files changed, 45 insertions(+), 46 deletions(-)
> --- a/arch/alpha/kernel/ptrace.c
> +++ b/arch/alpha/kernel/ptrace.c
> @@ -387,7 +387,7 @@ asmlinkage unsigned long syscall_trace_e
> * If this fails, seccomp may already have set up the return value
> * (e.g. SECCOMP_RET_ERRNO / TRACE).
> */
> - if (secure_computing() == -1) {
> + if (!seccomp_permit_syscall()) {
> if (regs->r19 == 0 && regs->r0 == (unsigned long)-1)
> syscall_set_return_value(current, regs, -ENOSYS, 0);
> syscall_set_nr(current, regs, -1);
> --- a/arch/arm/kernel/ptrace.c
> +++ b/arch/arm/kernel/ptrace.c
> @@ -855,7 +855,7 @@ asmlinkage int syscall_trace_enter(struc
>
> /* Do seccomp after ptrace; syscall may have changed. */
> #ifdef CONFIG_HAVE_ARCH_SECCOMP_FILTER
> - if (secure_computing() == -1)
> + if (!seccomp_permit_syscall())
> return -1;
> #else
> /* XXX: remove this once OABI gets fixed */
> --- a/arch/arm64/kernel/ptrace.c
> +++ b/arch/arm64/kernel/ptrace.c
> @@ -2420,7 +2420,7 @@ int syscall_trace_enter(struct pt_regs *
> }
>
> /* Do the secure computing after ptrace; failures should be fast. */
> - if (secure_computing() == -1)
> + if (!seccomp_permit_syscall())
> return NO_SYSCALL;
>
> if (test_thread_flag(TIF_SYSCALL_TRACEPOINT))
> --- a/arch/csky/kernel/ptrace.c
> +++ b/arch/csky/kernel/ptrace.c
> @@ -323,7 +323,7 @@ asmlinkage int syscall_trace_enter(struc
> if (ptrace_report_syscall_entry(regs))
> return -1;
>
> - if (secure_computing() == -1)
> + if (!seccomp_permit_syscall())
> return -1;
>
> if (test_thread_flag(TIF_SYSCALL_TRACEPOINT))
> --- a/arch/m68k/kernel/ptrace.c
> +++ b/arch/m68k/kernel/ptrace.c
> @@ -281,7 +281,7 @@ asmlinkage int syscall_trace_enter(void)
> if (test_thread_flag(TIF_SYSCALL_TRACE))
> ret = ptrace_report_syscall_entry(task_pt_regs(current));
>
> - if (secure_computing() == -1)
> + if (!seccomp_permit_syscall())
> return -1;
>
> return ret;
> --- a/arch/mips/kernel/ptrace.c
> +++ b/arch/mips/kernel/ptrace.c
> @@ -1328,7 +1328,7 @@ asmlinkage long syscall_trace_enter(stru
> return -1;
> }
>
> - if (secure_computing())
> + if (!seccomp_permit_syscall())
> return -1;
>
> if (unlikely(test_thread_flag(TIF_SYSCALL_TRACEPOINT)))
> --- a/arch/parisc/kernel/ptrace.c
> +++ b/arch/parisc/kernel/ptrace.c
> @@ -351,7 +351,7 @@ long do_syscall_trace_enter(struct pt_re
> }
>
> /* Do the secure computing check after ptrace. */
> - if (secure_computing() == -1)
> + if (!seccomp_permit_syscall())
> return -1;
>
> #ifdef CONFIG_HAVE_SYSCALL_TRACEPOINTS
> --- a/arch/sh/kernel/ptrace_32.c
> +++ b/arch/sh/kernel/ptrace_32.c
> @@ -460,7 +460,7 @@ asmlinkage long do_syscall_trace_enter(s
> return -1;
> }
>
> - if (secure_computing() == -1)
> + if (!seccomp_permit_syscall())
> return -1;
>
> if (unlikely(test_thread_flag(TIF_SYSCALL_TRACEPOINT)))
> --- a/arch/um/kernel/skas/syscall.c
> +++ b/arch/um/kernel/skas/syscall.c
> @@ -27,7 +27,7 @@ void handle_syscall(struct uml_pt_regs *
> goto out;
>
> /* Do the seccomp check after ptrace; failures should be fast. */
> - if (secure_computing() == -1)
> + if (!seccomp_permit_syscall())
> goto out;
>
> syscall = UPT_SYSCALL_NR(r);
> --- a/arch/x86/entry/vsyscall/vsyscall_64.c
> +++ b/arch/x86/entry/vsyscall/vsyscall_64.c
> @@ -118,10 +118,10 @@ static bool write_ok_or_segv(unsigned lo
>
> static bool __emulate_vsyscall(struct pt_regs *regs, unsigned long address)
> {
> - unsigned long caller;
> - int vsyscall_nr, syscall_nr, tmp;
> + unsigned long caller, orig_dx;
> + int vsyscall_nr, syscall_nr;
> + bool skip;
> long ret;
> - unsigned long orig_dx;
>
> /* Confirm that the fault happened in 64-bit user mode */
> if (!user_64bit_mode(regs))
> @@ -197,16 +197,16 @@ static bool __emulate_vsyscall(struct pt
> */
> regs->orig_ax = syscall_nr;
> regs->ax = -ENOSYS;
> - tmp = secure_computing();
> - if ((!tmp && regs->orig_ax != syscall_nr) || regs->ip != address) {
> + skip = !seccomp_permit_syscall();
> + if ((!skip && regs->orig_ax != syscall_nr) || regs->ip != address) {
> warn_bad_vsyscall(KERN_DEBUG, regs,
> "seccomp tried to change syscall nr or ip");
> force_exit_sig(SIGSYS);
> return true;
> }
> regs->orig_ax = -1;
> - if (tmp)
> - goto do_ret; /* skip requested */
> + if (skip)
> + goto do_ret;
>
> /*
> * With a real vsyscall, page faults cause SIGSEGV.
> --- a/arch/xtensa/kernel/ptrace.c
> +++ b/arch/xtensa/kernel/ptrace.c
> @@ -553,8 +553,7 @@ int do_syscall_trace_enter(struct pt_reg
> return 0;
> }
>
> - if (regs->syscall == NO_SYSCALL ||
> - secure_computing() == -1) {
> + if (regs->syscall == NO_SYSCALL || !seccomp_permit_syscall()) {
> do_syscall_trace_leave(regs);
> return 0;
> }
> --- a/include/linux/entry-common.h
> +++ b/include/linux/entry-common.h
> @@ -102,9 +102,8 @@ static __always_inline long syscall_trac
>
> /* Do seccomp after ptrace, to catch any tracer changes. */
> if (work & SYSCALL_WORK_SECCOMP) {
> - ret = __secure_computing();
> - if (ret == -1L)
> - return ret;
> + if (!__seccomp_permit_syscall())
> + return -1L;
> }
>
> /* Either of the above might have changed the syscall number */
> @@ -115,7 +114,7 @@ static __always_inline long syscall_trac
>
> syscall_enter_audit(regs, syscall);
>
> - return ret ? : syscall;
> + return syscall;
> }
>
> /**
> @@ -138,7 +137,7 @@ static __always_inline long syscall_trac
> * It handles the following work items:
> *
> * 1) syscall_work flag dependent invocations of
> - * ptrace_report_syscall_entry(), __secure_computing(), trace_sys_enter()
> + * ptrace_report_syscall_entry(), __seccomp_permit_syscall(),
> trace_sys_enter()
> * 2) Invocation of audit_syscall_entry()
> */
> static __always_inline long syscall_enter_from_user_mode_work(struct pt_regs
> *regs, long syscall)
> --- a/include/linux/seccomp.h
> +++ b/include/linux/seccomp.h
> @@ -22,14 +22,14 @@
> #include <linux/atomic.h>
> #include <asm/seccomp.h>
>
> -extern int __secure_computing(void);
> +extern bool __seccomp_permit_syscall(void);
>
> #ifdef CONFIG_HAVE_ARCH_SECCOMP_FILTER
> -static inline int secure_computing(void)
> +static __always_inline bool seccomp_permit_syscall(void)
> {
> if (unlikely(test_syscall_work(SECCOMP)))
> - return __secure_computing();
> - return 0;
> + return __seccomp_permit_syscall();
> + return true;
> }
> #else
> extern void secure_computing_strict(int this_syscall);
> @@ -50,11 +50,11 @@ static inline int seccomp_mode(struct se
> struct seccomp_data;
>
> #ifdef CONFIG_HAVE_ARCH_SECCOMP_FILTER
> -static inline int secure_computing(void) { return 0; }
> +static inline bool seccomp_permit_syscall(void) { return true; }
> #else
> static inline void secure_computing_strict(int this_syscall) { return; }
> #endif
> -static inline int __secure_computing(void) { return 0; }
> +static inline bool __seccomp_permit_syscall(void) { return true; }
>
> static inline long prctl_get_seccomp(void)
> {
> --- a/kernel/seccomp.c
> +++ b/kernel/seccomp.c
> @@ -1100,12 +1100,13 @@ void secure_computing_strict(int this_sy
> else
> BUG();
> }
> -int __secure_computing(void)
> +
> +bool __seccomp_permit_syscall(void)
> {
> int this_syscall = syscall_get_nr(current, current_pt_regs());
>
> secure_computing_strict(this_syscall);
> - return 0;
> + return true;
> }
> #else
>
> @@ -1256,7 +1257,7 @@ static int seccomp_do_user_notification(
> return -1;
> }
>
> -static int __seccomp_filter(int this_syscall, const bool recheck_after_trace)
> +static bool __seccomp_filter(int this_syscall, const bool
> recheck_after_trace)
> {
> u32 filter_ret, action;
> struct seccomp_data sd;
> @@ -1294,7 +1295,7 @@ static int __seccomp_filter(int this_sys
> case SECCOMP_RET_TRACE:
> /* We've been put in this state by the ptracer already. */
> if (recheck_after_trace)
> - return 0;
> + return true;
>
> /* ENOSYS these calls if there is no tracer attached. */
> if (!ptrace_event_enabled(current, PTRACE_EVENT_SECCOMP)) {
> @@ -1330,19 +1331,19 @@ static int __seccomp_filter(int this_sys
> * a skip would have already been reported.
> */
> if (__seccomp_filter(this_syscall, true))
> - return -1;
> + return false;
>
> - return 0;
> + return true;
>
> case SECCOMP_RET_USER_NOTIF:
> if (seccomp_do_user_notification(this_syscall, match, &sd))
> goto skip;
>
> - return 0;
> + return true;
>
> case SECCOMP_RET_LOG:
> seccomp_log(this_syscall, 0, action, true);
> - return 0;
> + return true;
>
> case SECCOMP_RET_ALLOW:
> /*
> @@ -1350,7 +1351,7 @@ static int __seccomp_filter(int this_sys
> * this action since SECCOMP_RET_ALLOW is the starting
> * state in seccomp_run_filters().
> */
> - return 0;
> + return true;
>
> case SECCOMP_RET_KILL_THREAD:
> case SECCOMP_RET_KILL_PROCESS:
> @@ -1367,46 +1368,46 @@ static int __seccomp_filter(int this_sys
> } else {
> do_exit(SIGSYS);
> }
> - return -1; /* skip the syscall go directly to signal handling */
> + return false; /* skip the syscall go directly to signal
> handling */
> }
>
> unreachable();
>
> skip:
> seccomp_log(this_syscall, 0, action, match ? match->log : false);
> - return -1;
> + return false;
> }
> #else
> -static int __seccomp_filter(int this_syscall, const bool recheck_after_trace)
> +static bool __seccomp_filter(int this_syscall, const bool
> recheck_after_trace)
> {
> BUG();
>
> - return -1;
> + return false;
> }
> #endif
>
> -int __secure_computing(void)
> +bool __seccomp_permit_syscall(void)
> {
> int mode = current->seccomp.mode;
> int this_syscall;
>
> if (IS_ENABLED(CONFIG_CHECKPOINT_RESTORE) &&
> unlikely(current->ptrace & PT_SUSPEND_SECCOMP))
> - return 0;
> + return true;
>
> this_syscall = syscall_get_nr(current, current_pt_regs());
>
> switch (mode) {
> case SECCOMP_MODE_STRICT:
> __secure_computing_strict(this_syscall); /* may call do_exit */
> - return 0;
> + return true;
> case SECCOMP_MODE_FILTER:
> return __seccomp_filter(this_syscall, false);
> /* Surviving SECCOMP_RET_KILL_* must be proactively impossible. */
> case SECCOMP_MODE_DEAD:
> WARN_ON_ONCE(1);
> do_exit(SIGKILL);
> - return -1;
> + return false;
> default:
> BUG();
> }
>
Reviewed-by: Mukesh Kumar Chaurasiya (IBM) <[email protected]>
