linux-kernel - Re: [PATCH v4 1/4] mm/gup: fix wrongly calculated returned value in fault_in_safe

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Message-ID: <Z/ipfCofBe99Ie+7@MiWiFi-R3L-srv>
Date: Fri, 11 Apr 2025 13:32:44 +0800
From: Baoquan He <bhe@...hat.com>
To: Andrew Morton <akpm@...ux-foundation.org>, agruenba@...hat.com,
	gfs2@...ts.linux.dev
Cc: linux-mm@...ck.org, david@...hat.com, osalvador@...e.de,
	yanjun.zhu@...ux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 1/4] mm/gup: fix wrongly calculated returned value in
 fault_in_safe_writeable()

On 04/10/25 at 08:43pm, Andrew Morton wrote:
> On Thu, 10 Apr 2025 11:57:14 +0800 Baoquan He <bhe@...hat.com> wrote:
> 
> > Not like fault_in_readable() or fault_in_writeable(), in
> > fault_in_safe_writeable() local variable 'start' is increased page
> > by page to loop till the whole address range is handled. However,
> > it mistakenly calcalates the size of handled range with 'uaddr - start'.
> 
> What are the userspace-visible runtime effects of this change?

I see it mainly affect gfs2_file_direct_read(). Not sure if GFS2 people
can sense any exceptional behaviour caused by this code bug.

>