Re: [PATCH] seccomp: passthrough uretprobe systemcall without filtering

[Oleg Nesterov <oleg@redhat.com>]

On 01/17, Masami Hiramatsu wrote:
>
> On Fri, 17 Jan 2025 02:39:28 +0100
> Oleg Nesterov <oleg@redhat.com> wrote:
>
> > A note for the seccomp maintainers...
> >
> > I don't know what do you think, but I agree in advance that the very fact this
> > patch adds "#ifdef CONFIG_X86_64" into __secure_computing() doesn't look nice.
> >
>
> Indeed. in_ia32_syscall() depends arch/x86 too.
> We can add an inline function like;
>
> ``` uprobes.h
> static inline bool is_uprobe_syscall(int syscall)
> {

We can, and this is what I tried to suggest from the very beginning.
But I agree with Eyal who decided to send the most trivial fix for
-stable, we can add the helper later.

I don't think it should live in uprobes.h and I'd prefer something
like arch_seccomp_ignored(int) but I won't insist.

> 	// arch_is_uprobe_syscall check can be replaced by Kconfig,
> 	// something like CONFIG_ARCH_URETPROBE_SYSCALL.

Or sysctl or both. This is another issue.

> ``` arch/x86/include/asm/uprobes.h
> #define arch_is_uprobe_syscall(syscall) \
> 	(IS_ENABLED(CONFIG_X86_64) && syscall == __NR_uretprobe && !in_ia32_syscall())
> ```

This won't compile if IS_ENABLED(CONFIG_X86_64) == false, __NR_uretprobe
will be undefined.

> > The problem is that we need a simple patch for -stable which fixes the real
> > problem. We can cleanup this logic later, I think.
>
> Hmm, at least we should make it is_uprobe_syscall() in uprobes.h so that
> do not pollute the seccomp subsystem with #ifdef.

See above. But I won't insist.

Oleg.