From: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
To: "Philippe Mathieu-Daudé" <philmd@oss.qualcomm.com>
Cc: Oleg Nesterov <oleg@redhat.com>, James Hogan <jhogan@kernel.org>,
Kees Cook <kees@kernel.org>,
linux-mips@vger.kernel.org, linux-kernel@vger.kernel.org,
Jiaxun Yang <jiaxun.yang@flygoat.com>
Subject: Re: [PATCH] MIPS: ptrace: Fix syscall skipping via PTRACE_SYSCALL
Date: Tue, 21 Jul 2026 17:04:34 +0200 [thread overview]
Message-ID: <al-KglT33I2jzUC7@alpha.franken.de> (raw)
In-Reply-To: <27072da0-124d-4a87-b037-f56320c8e97b@oss.qualcomm.com>
On Tue, Jul 21, 2026 at 04:43:40PM +0200, Philippe Mathieu-Daudé wrote:
> Hi Thomas,
>
> +Jiaxun
>
> On 17/7/26 13:27, Thomas Bogendoerfer wrote:
> > If tracer wanted to skip a syscall return value was always
> > overwritten with -ENOSYS. Fix this by checking against original
> > syscall number and only return -ENOSYS, if it is negative.
> >
> > Fixes: b6318a903d06 ("MIPS/ptrace: Pick up ptrace/seccomp changed syscalls")
>
> I think you meant:
>
> Fixes: 4370b673ccf2 ("MIPS: scall: Save thread_info.syscall unconditionally
> on entry")
no it was already broken before that commit.
b6318a903d06 reloads syscall number after tracehook_report_syscall_entry() so
the check for negative syscall is done with the "manipulated" syscall number.
And it the syscall should be skipped that number is -1.
Thomas.
--
Crap can work. Given enough thrust pigs will fly, but it's not necessarily a
good idea. [ RFC1925, 2.3 ]
prev parent reply other threads:[~2026-07-21 15:05 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-07-17 11:27 [PATCH] MIPS: ptrace: Fix syscall skipping via PTRACE_SYSCALL Thomas Bogendoerfer
2026-07-18 15:23 ` Oleg Nesterov
2026-07-21 14:43 ` Philippe Mathieu-Daudé
2026-07-21 15:04 ` Thomas Bogendoerfer [this message]
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