Some secdrivers (typically SELinux driver) generate unique
dynamic seclabel for each domain (unless a static one is
requested in domain XML). This is achieved by calling
qemuSecurityGenLabel() from qemuProcessPrepareDomain() which
allocates unique seclabel and stores it in domain def->seclabels.
The counterpart is qemuSecurityReleaseLabel() which releases the
label and removes it from def->seclabels. Problem is, that with
current code the qemuProcessStop() may still want to use the
seclabel after it was released, e.g. when it wants to restore the
label of a disk mirror.

What is happening now, is that in qemuProcessStop() the
qemuSecurityReleaseLabel() is called, which removes the SELinux
seclabel from def->seclabels, yada yada yada and eventually
qemuSecurityRestoreImageLabel() is called. This bubbles down to
virSecuritySELinuxRestoreImageLabelSingle() which find no SELinux
seclabel (using virDomainDefGetSecurityLabelDef()) and this
returns early doing nothing.

Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1751664
Fixes: 8fa0374c5b8e834fcbdeae674cc6cc9e6bf9019f
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
---
 src/qemu/qemu_process.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/qemu/qemu_process.c b/src/qemu/qemu_process.c
index 3b64caa619..15cf8cb666 100644
--- a/src/qemu/qemu_process.c
+++ b/src/qemu/qemu_process.c
@@ -7702,8 +7702,6 @@ void qemuProcessStop(virQEMUDriverPtr driver,
         qemuSecurityRestoreAllLabel(driver, vm,
                                     !!(flags & VIR_QEMU_PROCESS_STOP_MIGRATED));
 
-    qemuSecurityReleaseLabel(driver->securityManager, vm->def);
-
     for (i = 0; i < vm->def->ndisks; i++) {
         virDomainDeviceDef dev;
         virDomainDiskDefPtr disk = vm->def->disks[i];
@@ -7891,6 +7889,8 @@ void qemuProcessStop(virQEMUDriverPtr driver,
         }
     }
 
+    qemuSecurityReleaseLabel(driver->securityManager, vm->def);
+
     /* clear all private data entries which are no longer needed */
     qemuDomainObjPrivateDataClear(priv);
 
-- 
2.26.2

On 12/9/20 11:26 AM, Michal Privoznik wrote:
 >

Polite ping.

Michal

On Wed, Dec 09, 2020 at 11:26:52AM +0100, Michal Privoznik wrote:
> Some secdrivers (typically SELinux driver) generate unique
> dynamic seclabel for each domain (unless a static one is
> requested in domain XML). This is achieved by calling
> qemuSecurityGenLabel() from qemuProcessPrepareDomain() which
> allocates unique seclabel and stores it in domain def->seclabels.
> The counterpart is qemuSecurityReleaseLabel() which releases the
> label and removes it from def->seclabels. Problem is, that with
> current code the qemuProcessStop() may still want to use the
> seclabel after it was released, e.g. when it wants to restore the
> label of a disk mirror.
> 
> What is happening now, is that in qemuProcessStop() the
> qemuSecurityReleaseLabel() is called, which removes the SELinux
> seclabel from def->seclabels, yada yada yada and eventually
> qemuSecurityRestoreImageLabel() is called. This bubbles down to
> virSecuritySELinuxRestoreImageLabelSingle() which find no SELinux
> seclabel (using virDomainDefGetSecurityLabelDef()) and this
> returns early doing nothing.
> 
> Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1751664
> Fixes: 8fa0374c5b8e834fcbdeae674cc6cc9e6bf9019f
> Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
> ---
>  src/qemu/qemu_process.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)

Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>


Regards,
Daniel
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