linux-kernel - Re: [RFC PATCH 11/11] loop: Allow priveleged operations for root in the namespace which owns a device

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Date:	Fri, 23 May 2014 08:48:25 +0300
From:	Marian Marinov <mm@...com>
To:	Seth Forshee <seth.forshee@...onical.com>,
	linux-kernel@...r.kernel.org
CC:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jens Axboe <axboe@...nel.dk>, Arnd Bergmann <arnd@...db.de>,
	Eric Biederman <ebiederm@...ssion.com>,
	Serge Hallyn <serge.hallyn@...onical.com>,
	lxc-devel@...ts.linuxcontainers.org
Subject: Re: [RFC PATCH 11/11] loop: Allow priveleged operations for root
 in the namespace which owns a device

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One question about this patch.

Why don't you use the devices cgroup check if the root user in that namespace is allowed to use this device?

This way you can be sure that the root in that namespace can not access devices to which the host system did not gave
him access to.

Marian

On 05/15/2014 12:34 AM, Seth Forshee wrote:
> Signed-off-by: Seth Forshee <seth.forshee@...onical.com> --- drivers/block/loop.c | 14 +++++++++----- 1 file
> changed, 9 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/block/loop.c b/drivers/block/loop.c index 66bd938bcc1c..2cc19868ea0d 100644 ---
> a/drivers/block/loop.c +++ b/drivers/block/loop.c @@ -1074,7 +1074,7 @@ loop_set_status(struct loop_device *lo,
> const struct loop_info64 *info)
> 
> if (lo->lo_encrypt_key_size && !uid_eq(lo->lo_key_owner, uid) && -	    !capable(CAP_SYS_ADMIN)) +
> !ns_capable(disk_to_dev(lo->lo_disk)->ns, CAP_SYS_ADMIN)) return -EPERM; if (lo->lo_state != Lo_bound) return
> -ENXIO; @@ -1164,7 +1164,8 @@ loop_get_status(struct loop_device *lo, struct loop_info64 *info) 
> memcpy(info->lo_crypt_name, lo->lo_crypt_name, LO_NAME_SIZE); info->lo_encrypt_type = lo->lo_encryption ?
> lo->lo_encryption->number : 0; -	if (lo->lo_encrypt_key_size && capable(CAP_SYS_ADMIN)) { +	if
> (lo->lo_encrypt_key_size && +	    ns_capable(disk_to_dev(lo->lo_disk)->ns, CAP_SYS_ADMIN)) { 
> info->lo_encrypt_key_size = lo->lo_encrypt_key_size; memcpy(info->lo_encrypt_key, lo->lo_encrypt_key, 
> lo->lo_encrypt_key_size); @@ -1309,7 +1310,8 @@ static int lo_ioctl(struct block_device *bdev, fmode_t mode, 
> break; case LOOP_SET_STATUS: err = -EPERM; -		if ((mode & FMODE_WRITE) || capable(CAP_SYS_ADMIN)) +		if ((mode &
> FMODE_WRITE) || +		    ns_capable(disk_to_dev(lo->lo_disk)->ns, CAP_SYS_ADMIN)) err = loop_set_status_old(lo, 
> (struct loop_info __user *)arg); break; @@ -1318,7 +1320,8 @@ static int lo_ioctl(struct block_device *bdev,
> fmode_t mode, break; case LOOP_SET_STATUS64: err = -EPERM; -		if ((mode & FMODE_WRITE) || capable(CAP_SYS_ADMIN)) +
> if ((mode & FMODE_WRITE) || +		    ns_capable(disk_to_dev(lo->lo_disk)->ns, CAP_SYS_ADMIN)) err =
> loop_set_status64(lo, (struct loop_info64 __user *) arg); break; @@ -1327,7 +1330,8 @@ static int lo_ioctl(struct
> block_device *bdev, fmode_t mode, break; case LOOP_SET_CAPACITY: err = -EPERM; -		if ((mode & FMODE_WRITE) ||
> capable(CAP_SYS_ADMIN)) +		if ((mode & FMODE_WRITE) || +		    ns_capable(disk_to_dev(lo->lo_disk)->ns,
> CAP_SYS_ADMIN)) err = loop_set_capacity(lo, bdev); break; default:
> 


- -- 
Marian Marinov
Founder & CEO of 1H Ltd.
Jabber/GTalk: hackman@...ber.org
ICQ: 7556201
Mobile: +359 886 660 270
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