From: Al Viro <viro@zeniv.linux.org.uk>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Linux-MM <linux-mm@kvack.org>, Paul Mackerras <paulus@samba.org>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
linuxppc-dev <linuxppc-dev@lists.ozlabs.org>
Subject: Re: [PATCH v1 1/6] fs/readdir: Fix filldir() and filldir64() use of user_access_begin()
Date: Wed, 22 Jan 2020 17:41:29 +0000 [thread overview]
Message-ID: <20200122174129.GH23230@ZenIV.linux.org.uk> (raw)
In-Reply-To: <CAHk-=whTzEu5=sMEVLzuf7uOnoCyUs8wbfw87njes9FyE=mj1w@mail.gmail.com>
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@c-s.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...
WARNING: multiple messages have this Message-ID (diff)
From: Al Viro <viro@zeniv.linux.org.uk>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Christophe Leroy <christophe.leroy@c-s.fr>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Paul Mackerras <paulus@samba.org>,
Michael Ellerman <mpe@ellerman.id.au>,
Andrew Morton <akpm@linux-foundation.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
Linux-MM <linux-mm@kvack.org>
Subject: Re: [PATCH v1 1/6] fs/readdir: Fix filldir() and filldir64() use of user_access_begin()
Date: Wed, 22 Jan 2020 17:41:29 +0000 [thread overview]
Message-ID: <20200122174129.GH23230@ZenIV.linux.org.uk> (raw)
In-Reply-To: <CAHk-=whTzEu5=sMEVLzuf7uOnoCyUs8wbfw87njes9FyE=mj1w@mail.gmail.com>
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@c-s.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...
next prev parent reply other threads:[~2020-01-22 17:43 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-22 13:00 [PATCH v1 1/6] fs/readdir: Fix filldir() and filldir64() use of user_access_begin() Christophe Leroy
2020-01-22 13:00 ` Christophe Leroy
2020-01-22 13:00 ` [PATCH v1 2/6] powerpc/32s: Fix bad_kuap_fault() Christophe Leroy
2020-01-22 13:00 ` Christophe Leroy
2020-01-22 13:00 ` [PATCH v1 3/6] powerpc/kuap: Fix set direction in allow/prevent_user_access() Christophe Leroy
2020-01-22 13:00 ` Christophe Leroy
2020-01-22 13:00 ` [PATCH v1 4/6] powerpc/32s: Drop NULL addr verification Christophe Leroy
2020-01-22 13:00 ` Christophe Leroy
2020-01-22 13:00 ` [PATCH v1 5/6] powerpc/32s: prepare prevent_user_access() for user_access_end() Christophe Leroy
2020-01-22 13:00 ` Christophe Leroy
2020-01-22 13:00 ` [PATCH v1 6/6] powerpc: Implement user_access_begin and friends Christophe Leroy
2020-01-22 13:00 ` Christophe Leroy
2020-01-22 16:13 ` [PATCH v1 1/6] fs/readdir: Fix filldir() and filldir64() use of user_access_begin() Linus Torvalds
2020-01-22 16:13 ` Linus Torvalds
2020-01-22 17:41 ` Al Viro [this message]
2020-01-22 17:41 ` Al Viro
2020-01-22 17:54 ` Christophe Leroy
2020-01-22 17:54 ` Christophe Leroy
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