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Bug 1376810

Summary: selinux tries to mmap zero length file
Product: Red Hat Enterprise Linux 7 Reporter: Roman Bednář <rbednar>
Component: selinux-policyAssignee: Miroslav Grepl <mgrepl>
Status: CLOSED DUPLICATE QA Contact: BaseOS QE Security Team <qe-baseos-security>
Severity: unspecified Docs Contact:
Priority: unspecified    
Version: 7.2CC: lvrabec, mgrepl, mmalik, plautrba, pvrabec, ssekidde
Target Milestone: rc   
Target Release: ---   
Hardware: x86_64   
OS: Linux   
Whiteboard:
Fixed In Version: Doc Type: If docs needed, set a value
Doc Text:
Story Points: ---
Clone Of: Environment:
Last Closed: 2016-09-16 13:21:38 UTC Type: Bug
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:
Attachments:
Description Flags
debug log none

Description Roman Bednář 2016-09-16 12:52:59 UTC 
Created attachment 1201638 [details]
debug log

Selinux does not prevent mapping zero length files, causing errors in lvm commands output. This might not affect just lvm and it does not seems to affect functionality at all. The reproducer here might be a bit odd but I was not able to find another reliable one so far.

Reproducer:
1) install latest RHEL7
2) do not make any local fcontext changes
3) discover and login to ISCSI target
4) create partition on it as shown below
5) use the disk to create vg
6) observe  'mmap: Invalid argument' errors in lvm commands output


# fdisk -l /dev/sda
Disk /dev/sda: 1024 MB, 1024000000 bytes, 2000000 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 4194304 bytes
Disk label type: dos
Disk identifier: 0x78053651

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1            8192     1999999      995904   83  Linux

# lsblk -S
NAME HCTL       TYPE VENDOR   MODEL             REV TRAN
sda  2:0:0:0    disk LIO-ORG  FILEIO           4.0  iscsi

# getenforce
Permissive

# vgcreate vg /dev/sda1
mmap: Invalid argument
  Volume group "vg" successfully created

# lvs
mmap: Invalid argument
  LV   VG            Attr       LSize   Pool Origin Data%  Meta%  Move Log Cpy%Sync Convert
  root rhel_virt-148 -wi-ao----   6.74g                                                    
  swap rhel_virt-148 -wi-ao---- 828.00m 


This is most likely caused by selinux trying to mmap files that are of zero length at this point.
Those files should be:

/etc/selinux/targeted/contexts/files/file_contexts.local
/etc/selinux/targeted/contexts/files/file_contexts.local.bin

See attachment for debug log.

Additional info:
When any file context is changed on the system, those files get populated and errors are gone (same as with selinux disabled).


Packages:
3.10.0-501.el7.x86_64

libselinux-python-2.5-6.el7.x86_64
selinux-policy-3.13.1-96.el7.noarch
libselinux-2.5-6.el7.x86_64
libselinux-utils-2.5-6.el7.x86_64
selinux-policy-devel-3.13.1-96.el7.noarch
selinux-policy-targeted-3.13.1-96.el7.noarch
lvm2-2.02.165-1.el7    
lvm2-libs-2.02.165-1.el7    
lvm2-cluster-2.02.165-1.el7    
device-mapper-1.02.134-1.el7    
device-mapper-libs-1.02.134-1.el7 
device-mapper-event-1.02.134-1.el7 
device-mapper-event-libs-1.02.134-1.el7  
device-mapper-persistent-data-0.6.3-1.el7
cmirror-2.02.165-1.el7
Comment 1 Milos Malik 2016-09-16 13:05:27 UTC 
Already known as BZ#1372200.
Comment 2 Petr Lautrbach 2016-09-16 13:21:38 UTC 
While it's already fixed in selinux-policy-3.13.1-97.el7.noarch, you need to remove /etc/selinux/targeted/contexts/files/file_contexts.local.bin file if updated from an older version. And since we generally doesn't support upgrade from beta to final release, we won't provide any automatic fix for this issue, see https://bugzilla.redhat.com/show_bug.cgi?id=1374451#c5

*** This bug has been marked as a duplicate of bug 1372200 ***