On 7/8/2026 3:06 AM, 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(-)
As Ada pointed out, the description of secure_computing in arch/Kconfig
need to be updated, a possible suggestion:
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -636,8 +636,8 @@ config HAVE_ARCH_SECCOMP_FILTER
- syscall_rollback()
- syscall_set_return_value()
- SIGSYS siginfo_t support
- - secure_computing is called from a ptrace_event()-safe context
- - secure_computing return value is checked and a return value
of -1
+ - seccomp_permits_syscall is called from a ptrace_event()-safe
context
+ - seccomp_permits_syscall return value is checked and if false
Link:
https://lore.kernel.org/all/[email protected]/
> --- 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);
[...]
> -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;
The return value of __seccomp_filter is checked in the wrong way, check
-1 should be replaced with check false, maybe:
- if (__seccomp_filter(this_syscall, true))
- return -1;
+ if (!__seccomp_filter(this_syscall, true))
+ return false;
otherwise,
LGTM
Reviewed-by: Jinjie Ruan <[email protected]>
>
> - 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();
> }
>
