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Bug 1147923 - Resuming a block device (dm) changes its selinux context
Summary: Resuming a block device (dm) changes its selinux context
Keywords:
Status: CLOSED NOTABUG
Alias: None
Product: Red Hat Enterprise Linux 7
Classification: Red Hat
Component: systemd
Version: 7.1
Hardware: Unspecified
OS: Unspecified
unspecified
unspecified
Target Milestone: rc
: ---
Assignee: systemd-maint
QA Contact: qe-baseos-daemons
URL:
Whiteboard:
Depends On: 1147910 1189275 1265024
Blocks: 1122979
TreeView+ depends on / blocked
 
Reported: 2014-09-30 10:21 UTC by Federico Simoncelli
Modified: 2015-11-19 02:05 UTC (History)
14 users (show)

Fixed In Version:
Doc Type: Bug Fix
Doc Text:
Clone Of: 1147910
Environment:
Last Closed: 2014-10-17 14:46:45 UTC
Target Upstream Version:
Embargoed:

Attachments (Terms of Use)

Description Federico Simoncelli 2014-09-30 10:21:13 UTC 
+++ This bug was initially created as a clone of Bug #1147910 +++

Description of problem:
When a dm is resumed systemd-udevd changes its selinux context:

# dmsetup suspend 539cfcda--bc30--4e35--845e--888a58229e52-1d84a603--1a4a--461a--af1e--c1541f5f12b6

# ls -Z /dev/dm-4
brw-rw----. vdsm qemu system_u:object_r:svirt_image_t:s0 /dev/dm-4

# dmsetup resume 539cfcda--bc30--4e35--845e--888a58229e52-1d84a603--1a4a--461a--af1e--c1541f5f12b6

# ls -Z /dev/dm-4
brw-rw----. vdsm qemu system_u:object_r:fixed_disk_device_t:s0 /dev/dm-4

Version-Release number of selected component (if applicable):
systemd-208-22.fc20.x86_64

How reproducible:
100%

Steps to Reproduce:
1. start a VM on a dm device using libvirt
2. refresh the dm (needed for example after a resize, anyway dmsetup suspend/resume are enough to trigger the issue)

Actual results:
The VM is paused (or its IO fails, depending on the VM config) since it can't write to the dm anymore.

Expected results:
The VM should keep running (no IO failures) even after a refresh of the dm.

Additional info:

Debug + strace of /usr/lib/systemd/systemd-udevd:

RUN '/usr/sbin/dmsetup udevcomplete $env{DM_COOKIE}' /usr/lib/udev/rules.d/95-dm-notify.rules:12
handling device node '/dev/dm-4', devnum=b253:4, mode=0660, uid=36, gid=107
preserve permissions /dev/dm-4, 060660, uid=36, gid=107
[pid 23728] lsetxattr("/dev/dm-4", "security.selinux", "system_u:object_r:fixed_disk_device_t:s0", 41, 0) = 0
preserve already existing symlink '/dev/block/253:4' to '../dm-4'
[pid 23728] lsetxattr("/dev/block/253:4", "security.selinux", "system_u:object_r:device_t:s0", 30, 0) = 0
found 'b253:4' claiming '/run/udev/links/\x2f539cfcda-bc30-4e35-845e-888a58229e52\x2f1d84a603-1a4a-461a-af1e-c1541f5f12b6'
creating link '/dev/539cfcda-bc30-4e35-845e-888a58229e52/1d84a603-1a4a-461a-af1e-c1541f5f12b6' to '/dev/dm-4'
preserve already existing symlink '/dev/539cfcda-bc30-4e35-845e-888a58229e52/1d84a603-1a4a-461a-af1e-c1541f5f12b6' to '../dm-4'
[pid 23728] lsetxattr("/dev/539cfcda-bc30-4e35-845e-888a58229e52/1d84a603-1a4a-461a-af1e-c1541f5f12b6", "security.selinux", "system_u:object_r:device_t:s0", 30, 0) = 0
found 'b253:4' claiming '/run/udev/links/\x2fdisk\x2fby-id\x2fdm-name-539cfcda--bc30--4e35--845e--888a58229e52-1d84a603--1a4a--461a--af1e--c1541f5f12b6'
creating link '/dev/disk/by-id/dm-name-539cfcda--bc30--4e35--845e--888a58229e52-1d84a603--1a4a--461a--af1e--c1541f5f12b6' to '/dev/dm-4'
preserve already existing symlink '/dev/disk/by-id/dm-name-539cfcda--bc30--4e35--845e--888a58229e52-1d84a603--1a4a--461a--af1e--c1541f5f12b6' to '../../dm-4'
[pid 23728] lsetxattr("/dev/disk/by-id/dm-name-539cfcda--bc30--4e35--845e--888a58229e52-1d84a603--1a4a--461a--af1e--c1541f5f12b6", "security.selinux", "system_u:object_r:device_t:s0", 30, 0) = 0
found 'b253:4' claiming '/run/udev/links/\x2fdisk\x2fby-id\x2fdm-uuid-LVM-RBGwiMghcHZfY95VC5SeHFT20xaKJp1EIOBOK3Ejxq1FTfDKI4HngfgKoihn8G3p'
creating link '/dev/disk/by-id/dm-uuid-LVM-RBGwiMghcHZfY95VC5SeHFT20xaKJp1EIOBOK3Ejxq1FTfDKI4HngfgKoihn8G3p' to '/dev/dm-4'
preserve already existing symlink '/dev/disk/by-id/dm-uuid-LVM-RBGwiMghcHZfY95VC5SeHFT20xaKJp1EIOBOK3Ejxq1FTfDKI4HngfgKoihn8G3p' to '../../dm-4'
[pid 23728] lsetxattr("/dev/disk/by-id/dm-uuid-LVM-RBGwiMghcHZfY95VC5SeHFT20xaKJp1EIOBOK3Ejxq1FTfDKI4HngfgKoihn8G3p", "security.selinux", "system_u:object_r:device_t:s0", 30, 0) = 0
found 'b253:4' claiming '/run/udev/links/\x2fmapper\x2f539cfcda--bc30--4e35--845e--888a58229e52-1d84a603--1a4a--461a--af1e--c1541f5f12b6'
creating link '/dev/mapper/539cfcda--bc30--4e35--845e--888a58229e52-1d84a603--1a4a--461a--af1e--c1541f5f12b6' to '/dev/dm-4'
preserve already existing symlink '/dev/mapper/539cfcda--bc30--4e35--845e--888a58229e52-1d84a603--1a4a--461a--af1e--c1541f5f12b6' to '../dm-4'
[pid 23728] lsetxattr("/dev/mapper/539cfcda--bc30--4e35--845e--888a58229e52-1d84a603--1a4a--461a--af1e--c1541f5f12b6", "security.selinux", "system_u:object_r:device_t:s0", 30, 0) = 0
created db file '/run/udev/data/b253:4' for '/devices/virtual/block/dm-4'

--- Additional comment from Federico Simoncelli on 2014-09-30 05:54:14 EDT ---

It seems that as systemd-udevd is preserving the permissions:

 ...
 preserve permissions /dev/dm-4, 060660, uid=36, gid=107
 ...

it should also preserve the selinux context instead of resetting it with:

 ...
 lsetxattr("/dev/dm-4", "security.selinux", "system_u:object_r:fixed_disk_device_t:s0", 41, 0) = 0
 ...
Comment 2 Michal Skrivanek 2014-09-30 16:01:25 UTC 
Requesting 7.1 and 7.0.z due to RHEV dependency
Comment 3 Lukáš Nykrýn 2014-10-17 14:46:45 UTC 
This needs to be fixed in udev rule, not in udev.
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