From 427a75470c813205af2ea6bd81daacb0281ef58a Mon Sep 17 00:00:00 2001
Message-Id: <427a75470c813205af2ea6bd81daacb0281ef58a@dist-git>
From: Michal Privoznik <mprivozn@redhat.com>
Date: Wed, 25 Jul 2018 08:27:10 +0200
Subject: [PATCH] qemuDomainSaveMemory: Don't enforce dynamicOwnership
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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.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>
(cherry picked from commit 8c8c32339ae965fa6991462e98be1f5890ac7499)
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>
---
 src/qemu/qemu_driver.c | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index efd0a05c90..c7689cc239 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -3185,6 +3185,7 @@ qemuDomainSaveMemory(virQEMUDriverPtr driver,
                      unsigned int flags,
                      qemuDomainAsyncJob asyncJob)
 {
+    virQEMUDriverConfigPtr cfg = virQEMUDriverGetConfig(driver);
     bool needUnlink = false;
     int ret = -1;
     int fd = -1;
@@ -3202,9 +3203,10 @@ qemuDomainSaveMemory(virQEMUDriverPtr driver,
             goto cleanup;
         }
     }
-    fd = qemuOpenFile(driver, vm, path,
-                      O_WRONLY | O_TRUNC | O_CREAT | directFlag,
-                      &needUnlink);
+
+    fd = qemuOpenFileAs(cfg->user, cfg->group, false, path,
+                        O_WRONLY | O_TRUNC | O_CREAT | directFlag,
+                        &needUnlink);
     if (fd < 0)
         goto cleanup;
 
@@ -3244,6 +3246,7 @@ qemuDomainSaveMemory(virQEMUDriverPtr driver,
  cleanup:
     VIR_FORCE_CLOSE(fd);
     virFileWrapperFdFree(wrapperFd);
+    virObjectUnref(cfg);
 
     if (ret < 0 && needUnlink)
         unlink(path);
@@ -3793,9 +3796,9 @@ doCoreDump(virQEMUDriverPtr driver,
     /* Core dumps usually imply last-ditch analysis efforts are
      * desired, so we intentionally do not unlink even if a file was
      * created.  */
-    if ((fd = qemuOpenFile(driver, vm, path,
-                           O_CREAT | O_TRUNC | O_WRONLY | directFlag,
-                           NULL)) < 0)
+    if ((fd = qemuOpenFileAs(cfg->user, cfg->group, false, path,
+                             O_CREAT | O_TRUNC | O_WRONLY | directFlag,
+                             NULL)) < 0)
         goto cleanup;
 
     if (!(wrapperFd = virFileWrapperFdNew(&fd, path, flags)))
-- 
2.18.0