linux-kernel - Re: [PATCH] fs: clear file set[ug]id when writing via mmap

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Message-ID: <20151120010311.GA31728@1wt.eu>
Date:	Fri, 20 Nov 2015 02:03:11 +0100
From:	Willy Tarreau <w@....eu>
To:	Kees Cook <keescook@...omium.org>
Cc:	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Dave Chinner <david@...morbit.com>,
	Andy Lutomirski <luto@...capital.net>, Jan Kara <jack@...e.cz>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Mel Gorman <mgorman@...e.de>,
	Johannes Weiner <hannes@...xchg.org>,
	Rik van Riel <riel@...hat.com>,
	Matthew Wilcox <willy@...ux.intel.com>,
	Shachar Raindel <raindel@...lanox.com>,
	Boaz Harrosh <boaz@...xistor.com>,
	Michal Hocko <mhocko@...e.cz>,
	Haggai Eran <haggaie@...lanox.com>,
	Theodore Tso <tytso@...gle.com>,
	Dirk Steinmetz <public@...tdrjgfuzkfg.com>,
	Michael Kerrisk-manpages <mtk.manpages@...il.com>,
	Serge Hallyn <serge.hallyn@...ntu.com>,
	Seth Forshee <seth.forshee@...onical.com>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Linux FS Devel <linux-fsdevel@...r.kernel.org>,
	"Eric W . Biederman" <ebiederm@...ssion.com>,
	Serge Hallyn <serge.hallyn@...onical.com>, linux-mm@...ck.org
Subject: Re: [PATCH] fs: clear file set[ug]id when writing via mmap

On Fri, Nov 20, 2015 at 02:00:16AM +0100, Willy Tarreau wrote:
> > diff --git a/mm/memory.c b/mm/memory.c
> > index deb679c31f2a..4c970a4e0057 100644
> > --- a/mm/memory.c
> > +++ b/mm/memory.c
> > @@ -2036,6 +2036,7 @@ static inline int wp_page_reuse(struct mm_struct *mm,
> >  
> >  		if (!page_mkwrite)
> >  			file_update_time(vma->vm_file);
> > +		file_remove_privs(vma->vm_file);
> 
> I thought you said in one of the early mails of this thread that it
> didn't work. Or maybe I misunderstood.

OK never mind for this one I just saw the other mail where you said
the test is OK now. But I'm still worried about the performance so
the other point below remains :

> Also, don't you think we should move that into the if (!page_mkwrite)
> just like for the time update ?

Thanks!
Willy

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