Re: [libvirt] [PATCH 3/3] security_dac: Favour ACLs over chown()

On Wed, Aug 28, 2013 at 12:27:40PM +0200, Michal Privoznik wrote: > On filesystems supporting ACLs we don't need to do a chown but we > can just set ACLs to gain access for qemu. However, since we are > setting these on too low level, where we don't know if disk is > just a read only or read write, we set read write access > unconditionally. > > >From implementation POV, a reference counter is introduced, so ACL is > restored only on the last restore attempt in order to not cut off other > domains. And since a file may had an ACL for a user already set, we need > to keep this as well. Both these, the reference counter and original ACL > are stored as extended attributes named trusted.libvirt.dac.refCount and > trusted.libvirt.dac.oldACL respectively. > > However, some filesystems doesn't support ACLs, XATTRs, or both. So the > code is made to favour ACLs among with tracking the reference count. If > this fails, we fall back to chown() with best effort to remember the > original owner of file. > > Signed-off-by: Michal Privoznik <mprivozn(a)redhat.com&gt; > --- > src/security/security_dac.c | 297 +++++++++++++++++++++++++++++++++++++++----- > 1 file changed, 268 insertions(+), 29 deletions(-) > > diff --git a/src/security/security_dac.c b/src/security/security_dac.c > index 8cbb083..913b68e 100644 > --- a/src/security/security_dac.c > +++ b/src/security/security_dac.c > @@ -37,6 +37,9 @@ > > #define VIR_FROM_THIS VIR_FROM_SECURITY > #define SECURITY_DAC_NAME "dac" > +#define SECURITY_DAC_XATTR_OLD_ACL "trusted.libvirt.dac.oldACL" > +#define SECURITY_DAC_XATTR_OLD_OWNER "trusted.libvirt.dac.oldOwner" > +#define SECURITY_DAC_XATTR_REFCOUNT "trusted.libvirt.dac.refCount" Use of "trusted." is non-portable, per the long mail thread last time this was posted[1]. The discussion there was never resolved in any way, so NACK to this patch as is. Daniel [1] https://www.redhat.com/archives/libvir-list/2013-March/msg01610.html