From: Topi Miettinen <toiwoton@gmail.com>
To: Jann Horn <jannh@google.com>
Cc: Luis Chamberlain <mcgrof@kernel.org>,
Kees Cook <keescook@chromium.org>,
Alexey Dobriyan <adobriyan@gmail.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"open list:FILESYSTEMS (VFS and infrastructure)"
<linux-fsdevel@vger.kernel.org>,
Linux API <linux-api@vger.kernel.org>,
Christian Brauner <christian.brauner@ubuntu.com>
Subject: Re: [PATCH] Allow restricting permissions in /proc/sys
Date: Wed, 13 Nov 2019 18:19:17 +0200 [thread overview]
Message-ID: <13bc7935-8341-bb49-74ea-2eb58f72fd1f@gmail.com> (raw)
In-Reply-To: <CAG48ez0j_7NyCyvGn8U8NS2p=CQQb=me-5KTa7k5E6xpHJphaA@mail.gmail.com>
On 13.11.2019 18.00, Jann Horn wrote:
> On Wed, Nov 13, 2019 at 12:22 AM Christian Brauner
> <christian.brauner@ubuntu.com> wrote:
>> On Sun, Nov 03, 2019 at 04:55:48PM +0200, Topi Miettinen wrote:
>>> Several items in /proc/sys need not be accessible to unprivileged
>>> tasks. Let the system administrator change the permissions, but only
>>> to more restrictive modes than what the sysctl tables allow.
>>>
>>> Signed-off-by: Topi Miettinen <toiwoton@gmail.com>
>>> ---
>>> fs/proc/proc_sysctl.c | 41 +++++++++++++++++++++++++++++++----------
>>> 1 file changed, 31 insertions(+), 10 deletions(-)
>>>
>>> diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c
>>> index d80989b6c344..88c4ca7d2782 100644
>>> --- a/fs/proc/proc_sysctl.c
>>> +++ b/fs/proc/proc_sysctl.c
>>> @@ -818,6 +818,10 @@ static int proc_sys_permission(struct inode *inode, int
>>> mask)
>>> if ((mask & MAY_EXEC) && S_ISREG(inode->i_mode))
>>> return -EACCES;
>>>
>>> + error = generic_permission(inode, mask);
>>> + if (error)
>>> + return error;
>
> In kernel/ucount.c, the ->permissions handler set_permissions() grants
> access based on whether the caller has CAP_SYS_RESOURCE. And in
> net/sysctl_net.c, the handler net_ctl_permissions() grants access
> based on whether the caller has CAP_NET_ADMIN. This added check is
> going to break those, right?
>
Right. The comment above seems then a bit misleading:
/*
* sysctl entries that are not writeable,
* are _NOT_ writeable, capabilities or not.
*/
-Topi
next prev parent reply other threads:[~2019-11-13 16:19 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-03 14:55 [PATCH] Allow restricting permissions in /proc/sys Topi Miettinen
2019-11-03 17:56 ` Theodore Y. Ts'o
2019-11-03 19:24 ` Topi Miettinen
2019-11-12 23:15 ` Kees Cook
2019-11-03 18:50 ` Eric W. Biederman
2019-11-03 19:38 ` Topi Miettinen
2019-11-04 15:44 ` Eric W. Biederman
2019-11-04 17:58 ` Topi Miettinen
2019-11-04 23:41 ` Eric W. Biederman
2019-11-05 7:35 ` Topi Miettinen
2019-11-12 23:19 ` Kees Cook
2019-11-13 1:04 ` Luis Chamberlain
2019-11-12 23:22 ` Christian Brauner
2019-11-13 4:50 ` Andy Lutomirski
2019-11-13 10:52 ` Topi Miettinen
2019-11-13 16:00 ` Jann Horn
2019-11-13 16:19 ` Topi Miettinen [this message]
2019-11-13 16:40 ` Jann Horn
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