From: Christophe Leroy <christophe.leroy@c-s.fr>
To: Linus Torvalds <torvalds@linux-foundation.org>,
linux-arch <linux-arch@vger.kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
Linux-MM <linux-mm@kvack.org>
Subject: Re: [PATCH] lib: Reduce user_access_begin() boundaries in strncpy_from_user() and strnlen_user()
Date: Fri, 24 Jan 2020 07:25:51 +0100 [thread overview]
Message-ID: <8de7ba48-7bf4-8d43-5dfc-dacf34f80537@c-s.fr> (raw)
In-Reply-To: <CAHk-=wgcm5JzyacekDGQ4Ocoe-F5it-7-sbgU8oPnhwnSH3KAA@mail.gmail.com>
Le 23/01/2020 à 19:47, Linus Torvalds a écrit :
> On Thu, Jan 23, 2020 at 12:34 AM Christophe Leroy
> <christophe.leroy@c-s.fr> wrote:
>>
>> The range passed to user_access_begin() by strncpy_from_user() and
>> strnlen_user() starts at 'src' and goes up to the limit of userspace
>> allthough reads will be limited by the 'count' param.
>>
>> On 32 bits powerpc (book3s/32) access has to be granted for each 256Mbytes
>> segment and the cost increases with the number of segments to unlock.
>>
>> Limit the range with 'count' param.
>
> Ack. I'm tempted to take this for 5.5 too, just so that the
> unquestionably trivial fixes are in that baseline, and the
> infrastructure is ready for any architecture that has issues like
> this.
It would be nice, then the user_access_begin stuff for powerpc could go
for 5.6 without worring about.
Thanks
Christophe
prev parent reply other threads:[~2020-01-24 6:25 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-23 8:34 Christophe Leroy
2020-01-23 18:47 ` Linus Torvalds
2020-01-24 6:25 ` Christophe Leroy [this message]
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