Bug 664406
| Summary: | qemu process is spawned with no supplementary groups | ||
|---|---|---|---|
| Product: | Red Hat Enterprise Linux 6 | Reporter: | Dan Kenigsberg <danken> |
| Component: | libvirt | Assignee: | Laine Stump <laine> |
| Status: | CLOSED ERRATA | QA Contact: | Virtualization Bugs <virt-bugs> |
| Severity: | medium | Docs Contact: | |
| Priority: | urgent | ||
| Version: | 6.0 | CC: | bazulay, berrange, cpelland, dallan, dyuan, eblake, gren, hateya, jialiu, jyang, mgoldboi, plyons, vbian, xen-maint, ykaul, yoyzhang |
| Target Milestone: | rc | Keywords: | TestBlocker, ZStream |
| Target Release: | --- | ||
| Hardware: | Unspecified | ||
| OS: | Unspecified | ||
| Whiteboard: | |||
| Fixed In Version: | libvirt-0.8.7-1.el6 | Doc Type: | Bug Fix |
| Doc Text: | Story Points: | --- | |
| Clone Of: | Environment: | ||
| Last Closed: | 2011-05-19 13:25:06 UTC | Type: | --- |
| Regression: | --- | Mount Type: | --- |
| Documentation: | --- | CRM: | |
| Verified Versions: | Category: | --- | |
| oVirt Team: | --- | RHEL 7.3 requirements from Atomic Host: | |
| Cloudforms Team: | --- | Target Upstream Version: | |
| Embargoed: | |||
| Bug Depends On: | |||
| Bug Blocks: | 602640, 668692 | ||
Fix posted upstream. Once it's ACKed, this will be in the next libvirt release / rebase. https://www.redhat.com/archives/libvir-list/2010-December/msg00846.html BTW, the patches mentioned in Comment 2 were pushed upstream prior to the recent libvirt-0.8.7 release, so the fix will be in the upcoming rebase: commit f42cf7cb7902196382a65e5316c974a5c2106401 Author: Laine Stump <laine> Date: Tue Dec 21 15:34:41 2010 -0500 Replace setuid/setgid/initgroups with virSetUIDGID() This patch fixes https://bugzilla.redhat.com/show_bug.cgi?id=664406 If qemu is run as a different uid, it has been unable to access mode 0660 files that are owned by a different user, but with a group that the qemu is a member of (aside from the one group listed in the passwd file), because initgroups() is not being called prior to the exec. initgroups will change the group membership of the process (and its children) to match the new uid. To make this happen, the setregid()/setreuid() code in qemuSecurityDACSetProcessLabel has been replaced with a call to virSetUIDGID(), which does both of those, plus calls initgroups. Similar, but not identical, code in qemudOpenAsUID() has been replaced with virSetUIDGID(). This not only consolidates the functionality to a single location, but also potentially fixes some as-yet unreported bugs. commit d596c6dc9b64ca0c910a87127de72ed2ef47b692 Author: Laine Stump <laine> Date: Thu Dec 23 01:44:02 2010 -0500 new virSetUIDGID() utility function virSetUIDGID() sets both the real and effective group and user of the process, and additionally calls initgroups() to assure that the process joins all the auxiliary groups that the given uid is a member of. And one other related patch also made it into 0.8.7:
commit c685993d71c1cf561af2cf34a5077781566aa0e0
Author: Eric Blake <eblake>
Date: Mon Jan 3 15:26:33 2011 -0700
build: avoid compilation warnings
Detected on cygwin:
util/util.c: In function 'virSetUIDGID':
util/util.c:2824: warning: format '%d' expects type 'int', but argument 7 has type 'gid_t' [-Wformat]s)
* src/util/util.c (virSetUIDGID): Cast, as is done elsewhere in
this file, to avoid printf type mismatch warnings.
Built into libvirt-0.8.7-1.el6 The bug has been tested in libvirt-0.8.7-1.el6. 1, setup a NFS server with exports configuration as follows /tmp/nfstest *(rw,root_squash) 2, copy a guest image file into the shared fold. Using chmod to set the ownership and groupship of the image file to (otheruser):kvm, the other user shouldn't be qemu. # chown 500:36 rhel6.img 3, In the client server, mount the NFS shared folder, then, try to boot up a guest which use the image file as its OS disk. For the libvirt-0.8.7-1.el6, the guest started successfully, but libvirt-0.8.6-1.el6 failed. retested this bug with libvirt-0.8.7-6.el6.x86_64 --- verification pkg libvirt-0.8.1-27.el6.x86_64 --- reproducer pkg steps: 1, setup a NFS server with exports configuration as follows /tmp/nfstest *(rw,root_squash) 2, copy a guest image file into the shared fold. Using chmod+chown to set the access right ,ownership and groupship of the image file to (otheruser):kvm, the other user shouldn't be qemu. # chown 500:36 rhel6.img # chmod 755 rhel6.img 3, In the client machine, mount the NFS shared folder, then, try to boot up a guest which use the image file as its OS disk. [reproducer] error: Failed to start domain test1 error: internal error Process exited while reading console log output: char device redirected to /dev/pts/3 qemu: could not open disk image /var/lib/libvirt/migration/rhel6.img: Permission denied [verification] # virsh start test1 Domain test1 started # ll /var/lib/libvirt/migration/rhel6.img -rwxrwxrwx. 1 xguest kvm 8589934592 Feb 16 07:09 /var/lib/libvirt/migration/rhel6.img the ownership wasn't changed by qemu , and it kept kvm group . So set bug status to VERIFIED An advisory has been issued which should help the problem described in this bug report. This report is therefore being closed with a resolution of ERRATA. For more information on therefore solution and/or where to find the updated files, please follow the link below. You may reopen this bug report if the solution does not work for you. http://rhn.redhat.com/errata/RHBA-2011-0596.html |
Description of problem: By default, libvirt spawns qemu with qemu:qemu uid:gid. However, on RHEL6, qemu user has a default supplementary group ('kvm'). Without libvirt calling initgroups(), qemu process cannot enjoy the credentials of 'kvm' group. We need this in order for qemu to access group-readable ISO images with gid=kvm. Version-Release number of selected component (if applicable): libvirt-0.8.1-27.el6_0.2.x86_64 Upstream discussion under https://www.redhat.com/archives/libvir-list/2010-December/msg00756.html