linux-kernel - RE: [PATCH 2/3] x86/mce: Avoid infinite loop for copy from user recovery

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Message-ID: <fc4d994b02f643d480647edc4f2a7a29@intel.com>
Date:   Sat, 31 Jul 2021 20:43:13 +0000
From:   "Luck, Tony" <tony.luck@...el.com>
To:     Jue Wang <juew@...gle.com>
CC:     Borislav Petkov <bp@...en8.de>,
        "dinghui@...gfor.com.cn" <dinghui@...gfor.com.cn>,
        "huangcun@...gfor.com.cn" <huangcun@...gfor.com.cn>,
        "linux-edac@...r.kernel.org" <linux-edac@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        HORIGUCHI NAOYA(堀口 直也) 
        <naoya.horiguchi@....com>, Oscar Salvador <osalvador@...e.de>,
        x86 <x86@...nel.org>, "Song, Youquan" <youquan.song@...el.com>
Subject: RE: [PATCH 2/3] x86/mce: Avoid infinite loop for copy from user
 recovery

> After cherry picking patch 1 & 2, I saw the following with 2 UC errors injected
> into the user space buffer passed into write(2), as expected:
>
> [  287.994754] Kernel panic - not syncing: Machine checks to different
> user pages

Interesting.  What are the offsets of the two injected errors in your test (both
w.r.t. the start of the buffer, and within a page).

> The kernel tested with has its x86/mce and mm/memory-failure aligned with
> upstream till around 2020/11.
>
> Is there any other patch that I have missed to the write syscall etc?

There is a long series of patches from Al Viro to lib/iov_iter.c that are maybe
also relevent in making the kernel copy from user stop at the first poison
address in the buffer.

-Tony