Re: [PATCH v16 01/18] seccomp: Convert __secure_computing() to return boolean

[Ada Couprie Diaz <ada.coupriediaz@arm.com>]

Hi Jinjie,

On 29/06/2026 14:05, Jinjie Ruan wrote:
> 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.
Would it be relevant to mention that this fixes the unsound return value of
`syscall_trace_enter()` in generic entry, which motivated the patch 
initially[0] ?
> Suggested-by: Thomas Gleixner <tglx@kernel.org>
> Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
> ---
>   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 |  2 +-
>   arch/xtensa/kernel/ptrace.c           |  3 +--
>   include/linux/entry-common.h          |  7 +++---
>   include/linux/seccomp.h               | 10 ++++----
>   kernel/seccomp.c                      | 34 +++++++++++++--------------
>   14 files changed, 36 insertions(+), 38 deletions(-)

This is missing an update to the Kconfig documentation, a possible
suggestion :

diff --git a/arch/Kconfig b/arch/Kconfig
index fa7507ac8e13..9e3d40088afb 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -637,7 +637,7 @@ config HAVE_ARCH_SECCOMP_FILTER
           - 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
+         - secure_computing return value is checked and if false
             results in the system call being skipped immediately.
           - seccomp syscall wired up
           - if !HAVE_SPARSE_SYSCALL_NR, have SECCOMP_ARCH_NATIVE,

> [...]
> diff --git a/include/linux/entry-common.h b/include/linux/entry-common.h
> index 416a3352261f..3f66320e46d3 100644
> --- a/include/linux/entry-common.h
> +++ b/include/linux/entry-common.h
> @@ -100,9 +100,8 @@ static __always_inline long syscall_trace_enter(struct pt_regs *regs, unsigned l
>   
>   	/* Do seccomp after ptrace, to catch any tracer changes. */
>   	if (work & SYSCALL_WORK_SECCOMP) {
> -		ret = __secure_computing();
> -		if (ret == -1L)
> -			return ret;
> +		if (!__secure_computing())
> +			return -1L;
>   	}
>   
>   	/* Either of the above might have changed the syscall number */
> @@ -113,7 +112,7 @@ static __always_inline long syscall_trace_enter(struct pt_regs *regs, unsigned l
>   
>   	syscall_enter_audit(regs, syscall);
>   
> -	return ret ? : syscall;
> +	return syscall;
>   }
> [...]

Otherwise this feels like a more appropriate change with regards to
"safeguarding against new `secure_computing()` return value" !

With the updated Kconfig :
Reviewed-by: Ada Couprie Diaz <ada.coupriediaz@arm.com>

Thanks,
Ada

[0]: 
https://lore.kernel.org/r/20260511092103.1974980-2-ruanjinjie@huawei.com