[libvirt] [PATCH] initgroups() in qemudOpenAsUID()

[Dan Kenigsberg]

qemudOpenAsUID is intended to open a file with the credentials of a
specified uid. Current implementation fails if the file is accessible to
one of uid's groups but not owned by uid.

This patch replaces the supplementary group list that the child process
inherited from libvirtd with the default group list of uid.
---
 src/qemu/qemu_driver.c |   16 ++++++++++++++++
 1 files changed, 16 insertions(+), 0 deletions(-)

diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index 0ce2d40..a1027d4 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -6353,6 +6353,7 @@ parent_cleanup:
     char *buf = NULL;
     size_t bufsize = 1024 * 1024;
     int bytesread;
+    struct passwd *pwd;
 
     /* child doesn't need the read side of the pipe */
     close(pipefd[0]);
@@ -6365,6 +6366,21 @@ parent_cleanup:
         goto child_cleanup;
     }
 
+    /* we can avoid getpwuid_r() in threadless child */
+    if ((pwd = getpwuid(uid)) == NULL) {
+        exit_code = errno;
+        virReportSystemError(errno,
+                             _("cannot setuid(%d) to read '%s'"),
+                             uid, path);
+        goto child_cleanup;
+    }
+    if (initgroups(pwd->pw_name, pwd->pw_gid) != 0) {
+        exit_code = errno;
+        virReportSystemError(errno,
+                             _("cannot setuid(%d) to read '%s'"),
+                             uid, path);
+        goto child_cleanup;
+    }
     if (setuid(uid) != 0) {
         exit_code = errno;
         virReportSystemError(errno,
-- 
1.7.2.3