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From: Eric Biggers <ebiggers3@gmail.com>
To: Kees Cook <keescook@chromium.org>
Cc: "linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	Joe Lawrence <joe.lawrence@redhat.com>,
	Michael Kerrisk <mtk.manpages@gmail.com>,
	Willy Tarreau <w@1wt.eu>, Mikulas Patocka <mpatocka@redhat.com>,
	"Luis R . Rodriguez" <mcgrof@kernel.org>,
	LKML <linux-kernel@vger.kernel.org>,
	Eric Biggers <ebiggers@google.com>,
	"# 3.4.x" <stable@vger.kernel.org>
Subject: Re: [PATCH 3/7] pipe: actually allow root to exceed the pipe buffer limits
Date: Tue, 9 Jan 2018 18:34:45 -0800	[thread overview]
Message-ID: <20180110023445.GB931@zzz.localdomain> (raw)
In-Reply-To: <CAGXu5jK7XxcRD2kuEMvT4sHpZhyE=aVuQeARYH4upJXWJ4pb+w@mail.gmail.com>

On Tue, Jan 09, 2018 at 02:23:32PM -0800, Kees Cook wrote:
> On Sun, Jan 7, 2018 at 9:35 PM, Eric Biggers <ebiggers3@gmail.com> wrote:
> > From: Eric Biggers <ebiggers@google.com>
> >
> > pipe-user-pages-hard and pipe-user-pages-soft are only supposed to apply
> > to unprivileged users, as documented in both Documentation/sysctl/fs.txt
> > and the pipe(7) man page.
> >
> > However, the capabilities are actually only checked when increasing a
> > pipe's size using F_SETPIPE_SZ, not when creating a new pipe.
> > Therefore, if pipe-user-pages-hard has been set, the root user can run
> > into it and be unable to create pipes.  Similarly, if
> > pipe-user-pages-soft has been set, the root user can run into it and
> > have their pipes limited to 1 page each.
> >
> > Fix this by allowing the privileged override in both cases.
> 
> Should this be controlled per-namespace instead of via init-ns caps?
> 

I don't think so.  Users shouldn't be able to bypass the limits by creating a
user namespace.

Eric

  reply	other threads:[~2018-01-10  2:34 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-01-08  5:35 [PATCH 0/7] pipe: buffer limits fixes and cleanups Eric Biggers
2018-01-08  5:35 ` [PATCH 1/7] pipe, sysctl: drop 'min' parameter from pipe-max-size converter Eric Biggers
2018-01-09 22:20   ` Kees Cook
2018-01-10  2:29     ` Eric Biggers
2018-01-10 17:30       ` Kees Cook
2018-01-08  5:35 ` [PATCH 2/7] pipe, sysctl: remove pipe_proc_fn() Eric Biggers
2018-01-08  5:35 ` [PATCH 3/7] pipe: actually allow root to exceed the pipe buffer limits Eric Biggers
2018-01-09 22:23   ` Kees Cook
2018-01-10  2:34     ` Eric Biggers [this message]
2018-01-08  5:35 ` [PATCH 4/7] pipe: fix off-by-one error when checking " Eric Biggers
2018-01-08  6:42   ` Willy Tarreau
2018-01-08  5:35 ` [PATCH 5/7] pipe: reject F_SETPIPE_SZ with size over UINT_MAX Eric Biggers
2018-01-09 22:24   ` Kees Cook
2018-01-08  5:35 ` [PATCH 6/7] pipe: simplify round_pipe_size() Eric Biggers
2018-01-09 22:27   ` Kees Cook
2018-01-10  2:52     ` Eric Biggers
2018-01-10  3:13       ` Kees Cook
2018-01-08  5:35 ` [PATCH 7/7] pipe: read buffer limits atomically Eric Biggers
2018-01-09 22:27   ` Kees Cook

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