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

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Message-ID: <20150416150847.GA16917@azat>
Date:	Thu, 16 Apr 2015 18:08:47 +0300
From:	Azat Khuzhin <a3at.mail@...il.com>
To:	Wuqixuan <wuqixuan@...wei.com>
Cc:	viro@...iv.linux.org.uk, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] fs/sync.c : Add CAP_SYS_ADMIN checking before sync

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.
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