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Date: Thu, 2 Jul 2026 14:07:55 +0300
From: "Dmitry V. Levin" <ldv@strace.io>
To: Oleg Nesterov <oleg@redhat.com>
Cc: Renzo Davoli <renzo@cs.unibo.it>, linux-kernel@vger.kernel.org,
	Andrew Morton <akpm@linux-foundation.org>,
	Shuah Khan <shuah@kernel.org>, Alexey Gladkov <legion@kernel.org>,
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	strace-devel@lists.strace.io
Subject: Re: [PATCH 1/5] ptrace: add PTRACE_SYSCALL_INFO_SECCOMP_SKIP
Message-ID: <20260702110755.GA16303@strace.io>
References: <20260701150558.330348-1-renzo@cs.unibo.it>
 <20260701150558.330348-2-renzo@cs.unibo.it>
 <akYksXzCP4ioczEU@redhat.com>
 <akYoiowicHKWB3_J@cs.unibo.it>
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In-Reply-To: <akY2NlR4NXi-5O6v@redhat.com>

On Thu, Jul 02, 2026 at 11:58:14AM +0200, Oleg Nesterov wrote:
[...]
> @@ -1047,6 +1069,11 @@ ptrace_set_syscall_info_entry(struct task_struct *child, struct pt_regs *regs,
>  	if (nr != info->entry.nr)
>  		return -ERANGE;
>  
> +	syscall_set_nr(child, regs, nr);
> +	if (nr == -1)
> +		return __set_syscall_info_exit(child, regs,
> +						info->entry.rval, info->entry.is_error);

The kernel shouldn't suddenly start interpreting info->entry.rval and
info->entry.is_error because the current users of this interface are not
aware that the kernel might be doing it.  If we want to extend
PTRACE_SYSCALL_INFO_ENTRY/PTRACE_SYSCALL_INFO_SECCOMP this way, we would
have to require setting a flag in info->flags signalling the kernel that
the user requests this new behaviour.


-- 
ldv