[libvirt] [PATCH v2] qemuDomainSaveMemory: Don't enforce dynamicOwnership

[John Ferlan]

On 07/09/2018 08:51 AM, Michal Privoznik wrote:
> https://bugzilla.redhat.com/show_bug.cgi?id=1589115
> 
> When doing a memory snapshot qemuOpenFile() is used. This means
> that the file where memory is saved is firstly attempted to be
> created under root:root (because that's what libvirtd is running
> under) and if this fails the second attempt is done under
> domain's uid:gid. This does not make much sense - qemu is given
> opened FD so it does not need to access the file. Moreover, if
> dynamicOwnership is set in qemu.conf and the file lives on a
> squashed NFS this is deadly combination and very likely to fail.
> 
> The fix consists of using:
> 
>   qemuOpenFileAs(fallback_uid = cfg->user,
>                  fallback_gid = cfg->group,
>                  dynamicOwnership = false)
> 
> In other words, dynamicOwnership is turned off for memory
> snapshot (chown() will still be attempted if the file does not
> live on NFS) and instead of using domain DAC label, configured
> user:group is set as fallback.
> 

for memory snapshot and core files, right?

> Signed-off-by: Michal Privoznik <mprivozn at redhat.com>
> ---
> 
> Diff to v1:
> - Fix doCoreDump too (raised in review by John).
> 
>  src/qemu/qemu_driver.c | 15 +++++++++------
>  1 file changed, 9 insertions(+), 6 deletions(-)
> 

Strange - I had this marked as I replied to it, but obviously I didn't.
Wonder WTF happened ...

and the second qemuOpenFile in qemuDomainSaveMemory to touch up the
header (virQEMUSaveDataFinish) probably could use qemuOpenFileAs too
right?  although perhaps less important since the answer should be the
same, just the journey a little different.

Leaving just one consumer for qemuOpenFile and dynamic_ownership
manipulation.

Reviewed-by: John Ferlan <jferlan at redhat.com>

John