[libvirt] [PATCH] Call initgroups for qemu's uid prior to exec

[Laine Stump]

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). initgroups will change the group membership of the process (and
its children) to match the new uid.
---
 src/qemu/qemu_security_dac.c |   27 +++++++++++++++++++++++++++
 1 files changed, 27 insertions(+), 0 deletions(-)

diff --git a/src/qemu/qemu_security_dac.c b/src/qemu/qemu_security_dac.c
index 55dc0c6..2e60aec 100644
--- a/src/qemu/qemu_security_dac.c
+++ b/src/qemu/qemu_security_dac.c
@@ -12,6 +12,8 @@
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <fcntl.h>
+#include <pwd.h>
+#include <grp.h>
 
 #include "qemu_security_dac.h"
 #include "qemu_conf.h"
@@ -558,6 +560,30 @@ qemuSecurityDACSetProcessLabel(virSecurityDriverPtr drv ATTRIBUTE_UNUSED,
         }
     }
     if (driver->user) {
+        struct passwd pwd, *pwd_result;
+        char *buf = NULL;
+        size_t bufsize = 16384;
+
+        if (VIR_ALLOC_N(buf, bufsize) < 0) {
+            virReportOOMError();
+            return -1;
+        }
+        getpwuid_r(driver->user, &pwd, buf, bufsize, &pwd_result);
+        if (pwd_result == NULL) {
+            virReportSystemError(errno,
+                                 _("cannot getpwuid_r(%d)"), driver->user);
+            VIR_FREE(buf);
+            return -1;
+        }
+        if (initgroups(pwd.pw_name, pwd.pw_gid) != 0) {
+            virReportSystemError(errno,
+                                 _("cannot initgroups(\"%s\", %d)"),
+                                 pwd.pw_name, pwd.pw_gid);
+            VIR_FREE(buf);
+            return -1;
+        }
+        VIR_FREE(buf);
+
         if (setreuid(driver->user, driver->user) < 0) {
             virReportSystemError(errno,
                                  _("cannot change to '%d' user"),
@@ -566,6 +592,7 @@ qemuSecurityDACSetProcessLabel(virSecurityDriverPtr drv ATTRIBUTE_UNUSED,
         }
     }
 
+
     return 0;
 }
 
-- 
1.7.3.4