linux-kernel - Re: [PATCH] fs/sync.c : Add CAP_SYS

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAFLxGvzCzz-8ExDKOB_EncVp95gYE_bKsR8Z6S0ooApozW3dNA@mail.gmail.com>
Date:	Thu, 16 Apr 2015 21:31:21 +0200
From:	Richard Weinberger <richard.weinberger@...il.com>
To:	Azat Khuzhin <a3at.mail@...il.com>
Cc:	Wuqixuan <wuqixuan@...wei.com>, Al Viro <viro@...iv.linux.org.uk>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] fs/sync.c : Add CAP_SYS_ADMIN checking before sync

On Thu, Apr 16, 2015 at 5:08 PM, Azat Khuzhin <a3at.mail@...il.com> wrote:
> On Thu, Apr 16, 2015 at 07:43:34PM +0800, Wuqixuan wrote:
>> The process, supposed in one container, can't flush the metadata
>> and data of the all host's partitions without CAP_SYS_ADMIN
>> capability, like sys_mount is doing. The checking will prevent some
>> vicious programs impacting IO sequnces of those partitions,
>> particularly, the ones which can't be accessed in the container.
>>
>> Signed-off-by: Last Wu <wuqixuan@...wei.com>
>> ---
>> fs/sync.c | 3 +++
>> 1 file changed, 3 insertions(+)
>>
>> diff --git a/fs/sync.c b/fs/sync.c
>> index fbc98ee..9f07909 100644
>> --- a/fs/sync.c
>> +++ b/fs/sync.c
>> @@ -103,6 +103,9 @@ SYSCALL_DEFINE0(sync)
>> {
>> int nowait = 0, wait = 1;
>>
>> + if (!capable(CAP_SYS_ADMIN))
>> + return -EPERM;
>
> So after this patch I can't call sync as a regular user? (even without
> containers).
> But nothing in sync(2) says about special permissions for this.

Yeah, this solution will break userspace.
A much more generic solution would be to wait for cgroup aware writeback[1].
As temporary hack you can check whether the calling process is in the
initial pid namesapce to detect
a container calling sync(2)...

[1] https://lwn.net/Articles/628631/

-- 
Thanks,
//richard
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/