From aebbcdd33c8c18891f0bdbbf8924599a28152c9c Mon Sep 17 00:00:00 2001 From: Eric Blake Date: Mon, 23 Dec 2013 22:55:51 -0700 Subject: [PATCH] CVE-2013-6456: Avoid unsafe use of /proc/$PID/root in LXC shutdown/reboot code Use helper virProcessRunInMountNamespace in lxcDomainShutdownFlags and lxcDomainReboot. Otherwise, a malicious guest could use symlinks to force the host to manipulate the wrong file in the host's namespace. Idea by Dan Berrange, based on an initial report by Reco at http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=732394 Signed-off-by: Eric Blake --- src/lxc/lxc_driver.c | 38 ++++++++++++++++++++------------------ src/util/virinitctl.c | 26 ++++++++++---------------- src/util/virinitctl.h | 5 ++--- 3 files changed, 32 insertions(+), 37 deletions(-) diff --git a/src/lxc/lxc_driver.c b/src/lxc/lxc_driver.c index f1f7032794..4c3de06eab 100644 --- a/src/lxc/lxc_driver.c +++ b/src/lxc/lxc_driver.c @@ -3336,13 +3336,21 @@ lxcConnectListAllDomains(virConnectPtr conn, } +static int +lxcDomainInitctlCallback(pid_t pid ATTRIBUTE_UNUSED, + void *opaque) +{ + int *command = opaque; + return virInitctlSetRunLevel(*command); +} + + static int lxcDomainShutdownFlags(virDomainPtr dom, unsigned int flags) { virLXCDomainObjPrivatePtr priv; virDomainObjPtr vm; - char *vroot = NULL; int ret = -1; int rc; @@ -3369,16 +3377,14 @@ lxcDomainShutdownFlags(virDomainPtr dom, goto cleanup; } - if (virAsprintf(&vroot, "/proc/%llu/root", - (unsigned long long)priv->initpid) < 0) - goto cleanup; - if (flags == 0 || (flags & VIR_DOMAIN_SHUTDOWN_INITCTL)) { - if ((rc = virInitctlSetRunLevel(VIR_INITCTL_RUNLEVEL_POWEROFF, - vroot)) < 0) { + int command = VIR_INITCTL_RUNLEVEL_POWEROFF; + + if ((rc = virProcessRunInMountNamespace(priv->initpid, + lxcDomainInitctlCallback, + &command)) < 0) goto cleanup; - } if (rc == 0 && flags != 0 && ((flags & ~VIR_DOMAIN_SHUTDOWN_INITCTL) == 0)) { virReportError(VIR_ERR_OPERATION_UNSUPPORTED, "%s", @@ -3404,7 +3410,6 @@ lxcDomainShutdownFlags(virDomainPtr dom, ret = 0; cleanup: - VIR_FREE(vroot); if (vm) virObjectUnlock(vm); return ret; @@ -3416,13 +3421,13 @@ lxcDomainShutdown(virDomainPtr dom) return lxcDomainShutdownFlags(dom, 0); } + static int lxcDomainReboot(virDomainPtr dom, unsigned int flags) { virLXCDomainObjPrivatePtr priv; virDomainObjPtr vm; - char *vroot = NULL; int ret = -1; int rc; @@ -3449,16 +3454,14 @@ lxcDomainReboot(virDomainPtr dom, goto cleanup; } - if (virAsprintf(&vroot, "/proc/%llu/root", - (unsigned long long)priv->initpid) < 0) - goto cleanup; - if (flags == 0 || (flags & VIR_DOMAIN_REBOOT_INITCTL)) { - if ((rc = virInitctlSetRunLevel(VIR_INITCTL_RUNLEVEL_REBOOT, - vroot)) < 0) { + int command = VIR_INITCTL_RUNLEVEL_REBOOT; + + if ((rc = virProcessRunInMountNamespace(priv->initpid, + lxcDomainInitctlCallback, + &command)) < 0) goto cleanup; - } if (rc == 0 && flags != 0 && ((flags & ~VIR_DOMAIN_SHUTDOWN_INITCTL) == 0)) { virReportError(VIR_ERR_OPERATION_UNSUPPORTED, "%s", @@ -3484,7 +3487,6 @@ lxcDomainReboot(virDomainPtr dom, ret = 0; cleanup: - VIR_FREE(vroot); if (vm) virObjectUnlock(vm); return ret; diff --git a/src/util/virinitctl.c b/src/util/virinitctl.c index a85cc9cbc4..579268fb47 100644 --- a/src/util/virinitctl.c +++ b/src/util/virinitctl.c @@ -111,16 +111,18 @@ struct virInitctlRequest { # endif /* - * Send a message to init to change the runlevel + * Send a message to init to change the runlevel. This function is + * asynchronous-signal-safe (thus safe to use after fork of a + * multithreaded parent) - which is good, because it should only be + * used after forking and entering correct namespace. * * Returns 1 on success, 0 if initctl does not exist, -1 on error */ -int virInitctlSetRunLevel(virInitctlRunLevel level, - const char *vroot) +int +virInitctlSetRunLevel(virInitctlRunLevel level) { struct virInitctlRequest req; int fd = -1; - char *path = NULL; int ret = -1; memset(&req, 0, sizeof(req)); @@ -131,36 +133,28 @@ int virInitctlSetRunLevel(virInitctlRunLevel level, /* Yes it is an 'int' field, but wants a numeric character. Go figure */ req.runlevel = '0' + level; - if (vroot) { - if (virAsprintf(&path, "%s/%s", vroot, VIR_INITCTL_FIFO) < 0) - return -1; - } else { - if (VIR_STRDUP(path, VIR_INITCTL_FIFO) < 0) - return -1; - } - - if ((fd = open(path, O_WRONLY|O_NONBLOCK|O_CLOEXEC|O_NOCTTY)) < 0) { + if ((fd = open(VIR_INITCTL_FIFO, + O_WRONLY|O_NONBLOCK|O_CLOEXEC|O_NOCTTY)) < 0) { if (errno == ENOENT) { ret = 0; goto cleanup; } virReportSystemError(errno, _("Cannot open init control %s"), - path); + VIR_INITCTL_FIFO); goto cleanup; } if (safewrite(fd, &req, sizeof(req)) != sizeof(req)) { virReportSystemError(errno, _("Failed to send request to init control %s"), - path); + VIR_INITCTL_FIFO); goto cleanup; } ret = 1; cleanup: - VIR_FREE(path); VIR_FORCE_CLOSE(fd); return ret; } diff --git a/src/util/virinitctl.h b/src/util/virinitctl.h index 862539fcd6..6aeb1a66f7 100644 --- a/src/util/virinitctl.h +++ b/src/util/virinitctl.h @@ -1,7 +1,7 @@ /* * virinitctl.h: API for talking to init systems via initctl * - * Copyright (C) 2012 Red Hat, Inc. + * Copyright (C) 2012-2014 Red Hat, Inc. * * This library is free software; you can redistribute it and/or * modify it under the terms of the GNU Lesser General Public @@ -37,7 +37,6 @@ enum virInitctlRunLevel { VIR_INITCTL_RUNLEVEL_LAST }; -int virInitctlSetRunLevel(virInitctlRunLevel level, - const char *vroot); +int virInitctlSetRunLevel(virInitctlRunLevel level); #endif -- GitLab