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Date:   Fri, 24 Jul 2020 12:01:32 +0100
From:   Catalin Marinas <catalin.marinas@arm.com>
To:     Thomas Gleixner <tglx@linutronix.de>
Cc:     Andrei Vagin <avagin@gmail.com>, Will Deacon <will@kernel.org>,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        Vincenzo Frascino <vincenzo.frascino@arm.com>,
        Mark Rutland <mark.rutland@arm.com>,
        Dmitry Safonov <dima@arista.com>,
        Christian Brauner <christian.brauner@ubuntu.com>
Subject: Re: [PATCH v5 0/6] arm64: add the time namespace support
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On Thu, Jul 23, 2020 at 10:25:35PM +0200, Thomas Gleixner wrote:
> Andrei Vagin <avagin@gmail.com> writes:
> > On Wed, Jul 22, 2020 at 07:15:06PM +0100, Catalin Marinas wrote:
> >
> > I don't think that we need to handle this case in the kernel. Users
> > must understand what they are doing and have to write code so that avoid
> > these sort of situations. In general, I would say that in most cases it
> > is a bad idea to call setns from a signal handler.
> 
> This should not be supported in the first place and just let the
> offender die right there.

It would have been nice if we caught the offender easily but since
signal handling doesn't have to be paired with sigreturn(), the kernel
can't tell whether setns() is called in the wrong context. I guess we
just have to live with this (maybe document the restriction in
time_namespaces(7) or setns(2)).

-- 
Catalin