From: Christophe Leroy <christophe.leroy@c-s.fr>
To: Al Viro <viro@zeniv.linux.org.uk>,
Linus Torvalds <torvalds@linux-foundation.org>
Cc: 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 18:54:45 +0100 [thread overview]
Message-ID: <e6423f62-c29a-1a67-fb75-1330f5ef1348@c-s.fr> (raw)
In-Reply-To: <20200122174129.GH23230@ZenIV.linux.org.uk>
Le 22/01/2020 à 18:41, Al Viro a écrit :
> 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...
>
In v2, I'm covering from the beginning of parent dirent to the end of
current dirent.
Christophe
prev parent reply other threads:[~2020-01-22 17:54 UTC|newest]
Thread overview: 9+ 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 ` [PATCH v1 2/6] powerpc/32s: Fix bad_kuap_fault() 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 ` [PATCH v1 4/6] powerpc/32s: Drop NULL addr verification 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 ` [PATCH v1 6/6] powerpc: Implement user_access_begin and friends 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 17:41 ` Al Viro
2020-01-22 17:54 ` Christophe Leroy [this message]
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