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From: "Luck, Tony" <tony.luck@intel.com>
To: Borislav Petkov <bp@alien8.de>
Cc: "x86@kernel.org" <x86@kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"linux-mm@kvack.org" <linux-mm@kvack.org>,
	"Andy Lutomirski" <luto@kernel.org>,
	"Aili Yao" <yaoaili@kingsoft.com>,
	"HORIGUCHI NAOYA( 堀口 直也)" <naoya.horiguchi@nec.com>
Subject: RE: [PATCH 4/4] x86/mce: Avoid infinite loop for copy from user recovery
Date: Thu, 8 Apr 2021 16:06:10 +0000	[thread overview]
Message-ID: <89a1b424a211459ab522c0d2c3e8fc98@intel.com> (raw)
In-Reply-To: <20210408133631.GJ10192@zn.tnic>

> What I'm still unclear on, does this new version address that
> "mysterious" hang or panic which the validation team triggered or you
> haven't checked yet?

No :-(

They are triggering some case where multiple threads in a process hit the same
poison, and somehow memory_failure() fails to complete offlining the page. At this
point any other threads that hit that page get the early return from memory_failure
(because the page flags say it is poisoned) ... and so we loop.

But the "recover from cases where multiple machine checks happen
simultaneously" case is orthogonal to the "do the right thing to recover
when the kernel touches poison at a user address". So I think we can
tackle them separately

-Tony

  reply	other threads:[~2021-04-08 16:07 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-26  0:02 [RFC 0/4] Fix machine check recovery for copy_from_user Tony Luck
2021-03-26  0:02 ` [PATCH 1/4] x86/mce: Fix copyin code to return -EFAULT on machine check Tony Luck
2021-04-06 19:24   ` Borislav Petkov
2021-03-26  0:02 ` [PATCH 2/4] mce/iter: Check for copyin failure & return error up stack Tony Luck
2021-03-26  0:02 ` [PATCH 3/4] mce/copyin: fix to not SIGBUS when copying from user hits poison Tony Luck
2021-04-07 21:18   ` Borislav Petkov
2021-04-07 21:43     ` Luck, Tony
2021-04-08  8:49       ` Borislav Petkov
2021-04-08 17:08         ` Luck, Tony
2021-04-13 10:07           ` Borislav Petkov
2021-04-13 16:13             ` Luck, Tony
2021-04-14 13:05               ` Borislav Petkov
2021-03-26  0:02 ` [PATCH 4/4] x86/mce: Avoid infinite loop for copy from user recovery Tony Luck
2021-04-08 13:36   ` Borislav Petkov
2021-04-08 16:06     ` Luck, Tony [this message]
2021-04-08  2:13 ` [RFC 0/4] Fix machine check recovery for copy_from_user Aili Yao
2021-04-08 14:39   ` Luck, Tony
2021-04-09  6:49     ` Aili Yao
2021-04-19 21:28 [PATCH 4/4] x86/mce: Avoid infinite loop for copy from user recovery Jue Wang
2021-04-19 21:41 ` Luck, Tony

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