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Date: Fri, 20 Nov 2015 02:03:11 +0100
From: Willy Tarreau <w@1wt.eu>
To: Kees Cook <keescook@chromium.org>
Cc: linux-kernel@vger.kernel.org, Andrew Morton <akpm@linux-foundation.org>,
        Dave Chinner <david@fromorbit.com>,
        Andy Lutomirski <luto@amacapital.net>, Jan Kara <jack@suse.cz>,
        "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        Mel Gorman <mgorman@suse.de>, Johannes Weiner <hannes@cmpxchg.org>,
        Rik van Riel <riel@redhat.com>, Matthew Wilcox <willy@linux.intel.com>,
        Shachar Raindel <raindel@mellanox.com>,
        Boaz Harrosh <boaz@plexistor.com>, Michal Hocko <mhocko@suse.cz>,
        Haggai Eran <haggaie@mellanox.com>, Theodore Tso <tytso@google.com>,
        Dirk Steinmetz <public@rsjtdrjgfuzkfg.com>,
        Michael Kerrisk-manpages <mtk.manpages@gmail.com>,
        Serge Hallyn <serge.hallyn@ubuntu.com>,
        Seth Forshee <seth.forshee@canonical.com>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Linux FS Devel <linux-fsdevel@vger.kernel.org>,
        "Eric W . Biederman" <ebiederm@xmission.com>,
        Serge Hallyn <serge.hallyn@canonical.com>, linux-mm@kvack.org
Subject: Re: [PATCH] fs: clear file set[ug]id when writing via mmap
Message-ID: <20151120010311.GA31728@1wt.eu>
References: <20151120001043.GA28204@www.outflux.net> <20151120010016.GB31694@1wt.eu>
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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