linux-kernel - Re: [RFC PATCH] vfs: Fix might sleep in load_unaligned

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Message-ID: <20251127112035.129014-1-xieyuanbin1@huawei.com>
Date: Thu, 27 Nov 2025 19:20:35 +0800
From: Xie Yuanbin <xieyuanbin1@...wei.com>
To: <bigeasy@...utronix.de>, <viro@...iv.linux.org.uk>,
	<linux@...linux.org.uk>, <will@...nel.org>, <david.laight@...box.com>,
	<rmk+kernel@...linux.org.uk>
CC: <brauner@...nel.org>, <jack@...e.cz>, <nico@...xnic.net>,
	<akpm@...ux-foundation.org>, <hch@....de>, <jack@...e.com>,
	<wozizhi@...weicloud.com>, <linux-fsdevel@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <linux-arm-kernel@...ts.infradead.org>,
	<linux-mm@...ck.org>, <catalin.marinas@....com>, <rppt@...nel.org>,
	<vbabka@...e.cz>, <pfalcato@...e.de>, <lorenzo.stoakes@...cle.com>,
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	<lilinjie8@...wei.com>, <liaohua4@...wei.com>, <wangkefeng.wang@...wei.com>,
	<pangliyuan1@...wei.com>, Xie Yuanbin <xieyuanbin1@...wei.com>
Subject: Re: [RFC PATCH] vfs: Fix might sleep in load_unaligned_zeropad() with rcu read lock held

On, Thu, 27 Nov 2025 08:20:57 +0100, Sebastian Andrzej Siewior wrote:
> This all should be covered by the series here
> 	https://lore.kernel.org/all/20251110145555.2555055-1-bigeasy@linutronix.de/

Yes, I know it.

> or do I miss something.

We had some discussions about this bug:
Link: https://lore.kernel.org/lkml/20251126090505.3057219-1-wozizhi@huaweicloud.com/

The discussions:
Link: https://lore.kernel.org/CAHk-=wh1Wfwt9OFB4AfBbjyeu4JVZuSWQ4A8OoT3W6x9btddfw@mail.gmail.com
Link: https://lore.kernel.org/20251126192640.GD3538@ZenIV
Link: https://lore.kernel.org/aSeNtFxD1WRjFaiR@shell.armlinux.org.uk

According to the discussion, in do_page_fault(), when addr >= TASK_SIZE,
we should not try to acquire the mm read lock or find vma. Instead, we
should directly call __do_kernel_fault() or __do_user_fault(). Your
submission just moved harden_branch_predictor() forward. I think we can
have more discussions about the patches to fix the missing spectre.

I am trying to write a new patch, I hope it will better handle these two
bugs and be compatible with PREEMPT_RT scenarios.

> Sebastian

Thanks!

Xie Yuanbin