[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <20200122174129.GH23230@ZenIV.linux.org.uk>
Date: Wed, 22 Jan 2020 17:41:29 +0000
From: Al Viro <viro@...iv.linux.org.uk>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Christophe Leroy <christophe.leroy@....fr>,
Benjamin Herrenschmidt <benh@...nel.crashing.org>,
Paul Mackerras <paulus@...ba.org>,
Michael Ellerman <mpe@...erman.id.au>,
Andrew Morton <akpm@...ux-foundation.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
linux-fsdevel <linux-fsdevel@...r.kernel.org>,
Linux-MM <linux-mm@...ck.org>
Subject: Re: [PATCH v1 1/6] fs/readdir: Fix filldir() and filldir64() use of
user_access_begin()
On Wed, Jan 22, 2020 at 08:13:12AM -0800, Linus Torvalds wrote:
> On Wed, Jan 22, 2020 at 5:00 AM Christophe Leroy
> <christophe.leroy@....fr> wrote:
> >
> > Modify filldir() and filldir64() to request the real area they need
> > to get access to.
>
> Not like this.
>
> This makes the situation for architectures like x86 much worse, since
> you now use "put_user()" for the previous dirent filling. Which does
> that expensive user access setup/teardown twice again.
>
> So either you need to cover both the dirent's with one call, or you
> just need to cover the whole (original) user buffer passed in. But not
> this unholy mixing of both unsafe_put_user() and regular put_user().
I would suggest simply covering the range from dirent->d_off to
buf->current_dir->d_name[namelen]; they are going to be close to
each other and we need those addresses anyway...
Powered by blists - more mailing lists