From: Aili Yao <yaoaili@kingsoft.com>
To: Andy Lutomirski <luto@amacapital.net>
Cc: "Luck, Tony" <tony.luck@intel.com>,
Oleg Nesterov <oleg@redhat.com>,
Linux API <linux-api@vger.kernel.org>,
Andy Lutomirski <luto@kernel.org>,
HORIGUCHI NAOYA <naoya.horiguchi@nec.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
Peter Zijlstra <peterz@infradead.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
"H. Peter Anvin" <hpa@zytor.com>, X86 ML <x86@kernel.org>,
<yangfeng1@kingsoft.com>, Linux-MM <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>, <sunhao2@kingsoft.com>,
<yaoaili@kingsoft.com>, <suhua1@kingsoft.com>
Subject: Re: [PATCH v3] x86/fault: Send a SIGBUS to user process always for hwpoison page access.
Date: Thu, 11 Mar 2021 10:01:54 +0800 [thread overview]
Message-ID: <20210311100154.5a75c62e@alex-virtual-machine> (raw)
In-Reply-To: <CALCETrVqkK29n=6wtVhd7qgTWf83x3SUk6+bkD30asHyWSqppw@mail.gmail.com>
On Wed, 10 Mar 2021 17:28:12 -0800
Andy Lutomirski <luto@amacapital.net> wrote:
> On Wed, Mar 10, 2021 at 5:19 PM Aili Yao <yaoaili@kingsoft.com> wrote:
> >
> > On Mon, 8 Mar 2021 11:00:28 -0800
> > Andy Lutomirski <luto@amacapital.net> wrote:
> >
> > > > On Mar 8, 2021, at 10:31 AM, Luck, Tony <tony.luck@intel.com> wrote:
> > > >
> > > >
> > > >>
> > > >> Can you point me at that SIGBUS code in a current kernel?
> > > >
> > > > It is in kill_me_maybe(). mce_vaddr is setup when we disassemble whatever get_user()
> > > > or copy from user variant was in use in the kernel when the poison memory was consumed.
> > > >
> > > > if (p->mce_vaddr != (void __user *)-1l) {
> > > > force_sig_mceerr(BUS_MCEERR_AR, p->mce_vaddr, PAGE_SHIFT);
> > >
> > > Hmm. On the one hand, no one has complained yet. On the other hand, hardware that supports this isn’t exactly common.
> > >
> > > We may need some actual ABI design here. We also need to make sure that things like io_uring accesses or, more generally, anything using the use_mm / use_temporary_mm ends up either sending no signal or sending a signal to the right target.
> > >
> > > >
> > > > Would it be any better if we used the BUS_MCEERR_AO code that goes into siginfo?
> > >
> > > Dunno.
> >
> > I have one thought here but don't know if it's proper:
> >
> > Previous patch use force_sig_mceerr to the user process for such a scenario; with this method
> > The SIGBUS can't be ignored as force_sig_mceerr() was designed to.
> >
> > If the user process don't want this signal, will it set signal config to ignore?
> > Maybe we can use a send_sig_mceerr() instead of force_sig_mceerr(), if process want to
> > ignore the SIGBUS, then it will ignore that, or it can also process the SIGBUS?
>
> I don't think the signal blocking mechanism makes sense for this.
> Blocking a signal is for saying that, if another process sends the
> signal (or an async event like ctrl-C), then the process doesn't want
> it. Blocking doesn't block synchronous things like faults.
>
> I think we need to at least fix the existing bug before we add more
> signals. AFAICS the MCE_IN_KERNEL_COPYIN code is busted for kernel
> threads.
Got this, Thanks!
I read https://man7.org/linux/man-pages/man2/write.2.html, and it seems the write syscall is not expecting
an signal, maybe a specific error code for this scenario is enough.
--
Thanks!
Aili Yao
next prev parent reply other threads:[~2021-03-11 2:02 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-01 8:17 [PATCH v2] x86/fault: Send a SIGBUS to user process always for hwpoison page access Aili Yao
2021-02-01 16:58 ` Andy Lutomirski
2021-02-01 21:10 ` Luck, Tony
2021-02-01 22:09 ` Andy Lutomirski
2021-02-02 6:42 ` Aili Yao
2021-02-04 7:25 ` HORIGUCHI NAOYA(堀口 直也)
2021-02-05 5:06 ` Aili Yao
2021-02-05 9:01 ` [PATCH v3] " Aili Yao
2021-02-23 12:44 ` Aili Yao
2021-02-23 15:33 ` Andy Lutomirski
2021-02-23 16:42 ` Luck, Tony
2021-02-25 4:47 ` Aili Yao
2021-02-27 3:40 ` Andy Lutomirski
2021-03-01 7:57 ` Aili Yao
2021-03-01 18:12 ` Luck, Tony
2021-03-01 19:02 ` Luck, Tony
2021-03-01 19:09 ` Andy Lutomirski
2021-03-03 12:24 ` Aili Yao
2021-03-03 12:51 ` Aili Yao
2021-03-07 19:16 ` Andy Lutomirski
2021-03-08 9:49 ` Aili Yao
2021-03-08 18:14 ` Andy Lutomirski
2021-03-08 18:31 ` Luck, Tony
2021-03-08 19:00 ` Andy Lutomirski
2021-03-11 1:19 ` Aili Yao
2021-03-11 1:28 ` Andy Lutomirski
2021-03-11 2:01 ` Aili Yao [this message]
2021-03-11 16:52 ` Luck, Tony
2021-03-11 16:56 ` Peter Zijlstra
2021-03-09 2:14 ` Aili Yao
2021-03-09 2:25 ` Aili Yao
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