linux-kernel - Re: [PATCH v2 6/7] ptrace: introduce PTRACE_SET_SYSCALL

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Message-ID: <20250117144556.GB21203@redhat.com>
Date: Fri, 17 Jan 2025 15:45:57 +0100
From: Oleg Nesterov <oleg@...hat.com>
To: "Dmitry V. Levin" <ldv@...ace.io>
Cc: Eugene Syromyatnikov <evgsyr@...il.com>,
	Mike Frysinger <vapier@...too.org>,
	Renzo Davoli <renzo@...unibo.it>,
	Davide Berardi <berardi.dav@...il.com>,
	strace-devel@...ts.strace.io, linux-kernel@...r.kernel.org,
	linux-api@...r.kernel.org
Subject: Re: [PATCH v2 6/7] ptrace: introduce PTRACE_SET_SYSCALL_INFO request

On 01/16, Dmitry V. Levin wrote:
>
> The idea is to use "op" to specify the operation, and "flags" to specify
> future extensions to the operation.

OK,

> That is, the zero check implied by copy_struct_from_user() is not really
> needed here since the compatibility is tracked by "op" and "flags":

OK, but then why this patch uses copy_struct_from_user() ?

Why can't we simply do

	if (user_size != PTRACE_SYSCALL_INFO_SIZE_VER0)
		return -EINVAL;

	if (copy_from_user(..., user_size))
		return EFAULT;

now, until we add the extensions ?

Oleg.