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From: Kees Cook <keescook@chromium.org>
To: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Vlastimil Babka <vbabka@suse.cz>,
	Luis Chamberlain <mcgrof@kernel.org>,
	Iurii Zaikin <yzaikin@google.com>,
	linux-kernel@vger.kernel.org, linux-api@vger.kernel.org,
	linux-mm@kvack.org, Ivan Teterevkov <ivan.teterevkov@nutanix.com>,
	Michal Hocko <mhocko@kernel.org>,
	David Rientjes <rientjes@google.com>,
	Matthew Wilcox <willy@infradead.org>,
	"Guilherme G . Piccoli" <gpiccoli@canonical.com>
Subject: Re: [RFC v2 1/2] kernel/sysctl: support setting sysctl parameters from kernel command line
Date: Wed, 25 Mar 2020 15:54:09 -0700
Message-ID: <202003251544.7ECB392A7@keescook> (raw)
In-Reply-To: <874kuc5b5z.fsf@x220.int.ebiederm.org>

On Wed, Mar 25, 2020 at 05:20:40PM -0500, Eric W. Biederman wrote:
> Hmm.  There is a big gotcha in here and I think it should be mentioned.
> This code only works because no one has done set_fs(KERNEL_DS).  Which
> means this only works with strings that are kernel addresses essentially
> by mistake.  A big fat comment documenting why it is safe to pass in
> kernel addresses to a function that takes a "char __user*" pointer
> would be very good.

Yeah, I was going to mention this too just now as I went looking through
one of the handlers and was reminded that the args are marked __user. :P

I suspect we might need to add some __force __user markings or something
(with a comment as you say above), to keep sparse from going crazy. :)

-- 
Kees Cook

  reply index

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-25 12:03 Vlastimil Babka
2020-03-25 12:03 ` [RFC v2 2/2] kernel/sysctl: support handling command line aliases Vlastimil Babka
2020-03-25 14:29   ` Michal Hocko
2020-03-25 14:36     ` Vlastimil Babka
2020-03-25 14:44       ` Michal Hocko
2020-03-25 22:42   ` Kees Cook
2020-03-29 15:00   ` Arvind Sankar
2020-03-25 21:21 ` [RFC v2 1/2] kernel/sysctl: support setting sysctl parameters from kernel command line Kees Cook
2020-03-26  9:30   ` Vlastimil Babka
2020-03-25 22:20 ` Eric W. Biederman
2020-03-25 22:54   ` Kees Cook [this message]
2020-03-26  6:58   ` Michal Hocko
2020-03-26  7:21     ` Kees Cook
2020-03-26 12:45     ` Eric W. Biederman
2020-03-30 22:09       ` Luis Chamberlain
2020-03-26 13:30     ` Christian Brauner
2020-03-26 13:39       ` Michal Hocko
2020-03-26 13:29   ` Vlastimil Babka

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