[libvirt] [PATCH] daemon: Fix core dumps if unix_sock_group is set
Setting unix_sock_group to something else than default "root" in
/etc/libvirt/libvirtd.conf prevents system libvirtd from dumping core on
crash. This is because we used setgid(unix_sock_group) before binding to
/var/run/libvirt/libvirt-sock* and setgid() back to original group.
However, if a process changes its effective or filesystem group ID, it
will be forbidden from leaving core dumps unless fs.suid_dumpable sysctl
is set to something else then 0 (and it is 0 by default).
Changing socket's group ownership after bind works better. And we can do
so without introducing a race condition since we loosen access rights by
changing the group from root to something else.
---
daemon/libvirtd.c | 17 ++++++++---------
1 files changed, 8 insertions(+), 9 deletions(-)
diff --git a/daemon/libvirtd.c b/daemon/libvirtd.c
index 2df9337..b1539b1 100644
--- a/daemon/libvirtd.c
+++ b/daemon/libvirtd.c
@@ -542,7 +542,6 @@ static int qemudListenUnix(struct qemud_server *server,
char *path, int readonly, int auth) {
struct qemud_socket *sock;
mode_t oldmask;
- gid_t oldgrp;
char ebuf[1024];
if (VIR_ALLOC(sock) < 0) {
@@ -579,21 +578,21 @@ static int qemudListenUnix(struct qemud_server *server,
if (sock->addr.data.un.sun_path[0] == '@')
sock->addr.data.un.sun_path[0] = '\0';
- oldgrp = getgid();
oldmask = umask(readonly ? ~unix_sock_ro_mask : ~unix_sock_rw_mask);
- if (server->privileged && setgid(unix_sock_gid)) {
- VIR_ERROR(_("Failed to set group ID to %d"), unix_sock_gid);
- goto cleanup;
- }
-
if (bind(sock->fd, &sock->addr.data.sa, sock->addr.len) < 0) {
VIR_ERROR(_("Failed to bind socket to '%s': %s"),
path, virStrerror(errno, ebuf, sizeof ebuf));
goto cleanup;
}
umask(oldmask);
- if (server->privileged && setgid(oldgrp)) {
- VIR_ERROR(_("Failed to restore group ID to %d"), oldgrp);
+
+ /* chown() doesn't work for abstract sockets but we use them only
+ * if libvirtd runs unprivileged
+ */
+ if (server->privileged && chown(path, -1, unix_sock_gid)) {
+ VIR_ERROR(_("Failed to change group ID of '%s' to %d: %s"),
+ path, unix_sock_gid,
+ virStrerror(errno, ebuf, sizeof ebuf));
goto cleanup;
}
--
1.7.4.rc1