From e0622ca28163f2b4a5fbf40266bbc30986acee14 Mon Sep 17 00:00:00 2001 From: Jim Fehlig Date: Mon, 21 Jan 2013 10:09:05 -0700 Subject: [PATCH] libxl: Fix races in libxl event code The libxl driver is racy in it's interactions with libxl and libvirt's event loop. The event loop can invoke callbacks after libxl has deregistered the event, and possibly access freed data associated with the event. This patch fixes the race by converting libxlDomainObjPrivate to a virObjectLockable, and locking it while executing libxl upcalls and libvirt event loop callbacks. Note that using the virDomainObj lock is not satisfactory since it may be desirable to hold the virDomainObj lock even when libxl events such as reading and writing to xenstore need processed. --- src/libxl/libxl_conf.h | 5 +- src/libxl/libxl_driver.c | 140 +++++++++++++++++++++++---------------- 2 files changed, 88 insertions(+), 57 deletions(-) diff --git a/src/libxl/libxl_conf.h b/src/libxl/libxl_conf.h index a3cce080a1..8617d312c7 100644 --- a/src/libxl/libxl_conf.h +++ b/src/libxl/libxl_conf.h @@ -1,5 +1,5 @@ /*---------------------------------------------------------------------------*/ -/* Copyright (c) 2011 SUSE LINUX Products GmbH, Nuernberg, Germany. +/* Copyright (C) 2011-2013 SUSE LINUX Products GmbH, Nuernberg, Germany. * Copyright (C) 2011 Univention GmbH. * * This library is free software; you can redistribute it and/or @@ -35,6 +35,7 @@ # include "capabilities.h" # include "configmake.h" # include "virportallocator.h" +# include "virobject.h" # define LIBXL_VNC_PORT_MIN 5900 @@ -81,6 +82,8 @@ struct _libxlDriverPrivate { typedef struct _libxlDomainObjPrivate libxlDomainObjPrivate; typedef libxlDomainObjPrivate *libxlDomainObjPrivatePtr; struct _libxlDomainObjPrivate { + virObjectLockable parent; + /* per domain libxl ctx */ libxl_ctx *ctx; libxl_evgen_domain_death *deathW; diff --git a/src/libxl/libxl_driver.c b/src/libxl/libxl_driver.c index 0e2c9cd879..a34be51efe 100644 --- a/src/libxl/libxl_driver.c +++ b/src/libxl/libxl_driver.c @@ -59,18 +59,16 @@ /* Number of Xen scheduler parameters */ #define XEN_SCHED_CREDIT_NPARAM 2 -struct libxlOSEventHookFDInfo { - libxlDomainObjPrivatePtr priv; - void *xl_priv; - int watch; -}; - -struct libxlOSEventHookTimerInfo { +/* Object used to store info related to libxl event registrations */ +typedef struct _libxlEventHookInfo libxlEventHookInfo; +typedef libxlEventHookInfo *libxlEventHookInfoPtr; +struct _libxlEventHookInfo { libxlDomainObjPrivatePtr priv; void *xl_priv; int id; }; +static virClassPtr libxlDomainObjPrivateClass; static libxlDriverPrivatePtr libxl_driver = NULL; /* Function declarations */ @@ -84,6 +82,20 @@ libxlVmStart(libxlDriverPrivatePtr driver, virDomainObjPtr vm, bool start_paused, int restore_fd); /* Function definitions */ +static int +libxlDomainObjPrivateOnceInit(void) +{ + if (!(libxlDomainObjPrivateClass = virClassNew(virClassForObjectLockable(), + "libxlDomainObjPrivate", + sizeof(libxlDomainObjPrivate), + NULL))) + return -1; + + return 0; +} + +VIR_ONCE_GLOBAL_INIT(libxlDomainObjPrivate) + static void libxlDriverLock(libxlDriverPrivatePtr driver) { @@ -96,15 +108,22 @@ libxlDriverUnlock(libxlDriverPrivatePtr driver) virMutexUnlock(&driver->lock); } +static void +libxlEventHookInfoFree(void *obj) +{ + VIR_FREE(obj); +} + static void libxlFDEventCallback(int watch ATTRIBUTE_UNUSED, int fd, int vir_events, void *fd_info) { - struct libxlOSEventHookFDInfo *info = fd_info; + libxlEventHookInfoPtr info = fd_info; int events = 0; + virObjectLock(info->priv); if (vir_events & VIR_EVENT_HANDLE_READABLE) events |= POLLIN; if (vir_events & VIR_EVENT_HANDLE_WRITABLE) @@ -114,42 +133,37 @@ libxlFDEventCallback(int watch ATTRIBUTE_UNUSED, if (vir_events & VIR_EVENT_HANDLE_HANGUP) events |= POLLHUP; + virObjectUnlock(info->priv); libxl_osevent_occurred_fd(info->priv->ctx, info->xl_priv, fd, 0, events); } -static void -libxlFreeFDInfo(void *obj) -{ - VIR_FREE(obj); -} - static int libxlFDRegisterEventHook(void *priv, int fd, void **hndp, short events, void *xl_priv) { int vir_events = VIR_EVENT_HANDLE_ERROR; - struct libxlOSEventHookFDInfo *fdinfo; + libxlEventHookInfoPtr info; - if (VIR_ALLOC(fdinfo) < 0) { + if (VIR_ALLOC(info) < 0) { virReportOOMError(); return -1; } - fdinfo->priv = priv; - fdinfo->xl_priv = xl_priv; - *hndp = fdinfo; - if (events & POLLIN) vir_events |= VIR_EVENT_HANDLE_READABLE; if (events & POLLOUT) vir_events |= VIR_EVENT_HANDLE_WRITABLE; - fdinfo->watch = virEventAddHandle(fd, vir_events, libxlFDEventCallback, - fdinfo, libxlFreeFDInfo); - if (fdinfo->watch < 0) { - VIR_FREE(fdinfo); - return fdinfo->watch; + info->id = virEventAddHandle(fd, vir_events, libxlFDEventCallback, + info, libxlEventHookInfoFree); + if (info->id < 0) { + VIR_FREE(info); + return -1; } + info->priv = priv; + info->xl_priv = xl_priv; + *hndp = info; + return 0; } @@ -159,15 +173,18 @@ libxlFDModifyEventHook(void *priv ATTRIBUTE_UNUSED, void **hndp, short events) { - struct libxlOSEventHookFDInfo *fdinfo = *hndp; + libxlEventHookInfoPtr info = *hndp; int vir_events = VIR_EVENT_HANDLE_ERROR; + virObjectLock(info->priv); if (events & POLLIN) vir_events |= VIR_EVENT_HANDLE_READABLE; if (events & POLLOUT) vir_events |= VIR_EVENT_HANDLE_WRITABLE; - virEventUpdateHandle(fdinfo->watch, vir_events); + virEventUpdateHandle(info->id, vir_events); + virObjectUnlock(info->priv); + return 0; } @@ -176,16 +193,21 @@ libxlFDDeregisterEventHook(void *priv ATTRIBUTE_UNUSED, int fd ATTRIBUTE_UNUSED, void *hnd) { - struct libxlOSEventHookFDInfo *fdinfo = hnd; + libxlEventHookInfoPtr info = hnd; + libxlDomainObjPrivatePtr p = info->priv; - virEventRemoveHandle(fdinfo->watch); + virObjectLock(p); + virEventRemoveHandle(info->id); + virObjectUnlock(p); } static void libxlTimerCallback(int timer ATTRIBUTE_UNUSED, void *timer_info) { - struct libxlOSEventHookTimerInfo *info = timer_info; + libxlEventHookInfoPtr info = timer_info; + libxlDomainObjPrivatePtr p = info->priv; + virObjectLock(p); /* * libxl expects the event to be deregistered when calling * libxl_osevent_occurred_timeout, but we dont want the event info @@ -193,14 +215,11 @@ libxlTimerCallback(int timer ATTRIBUTE_UNUSED, void *timer_info) * from libxl. */ virEventUpdateTimeout(info->id, -1); - libxl_osevent_occurred_timeout(info->priv->ctx, info->xl_priv); + virObjectUnlock(p); + libxl_osevent_occurred_timeout(p->ctx, info->xl_priv); + virObjectLock(p); virEventRemoveTimeout(info->id); -} - -static void -libxlTimerInfoFree(void* obj) -{ - VIR_FREE(obj); + virObjectUnlock(p); } static int @@ -209,13 +228,13 @@ libxlTimeoutRegisterEventHook(void *priv, struct timeval abs_t, void *xl_priv) { + libxlEventHookInfoPtr info; struct timeval now; struct timeval res; static struct timeval zero; - struct libxlOSEventHookTimerInfo *timer_info; - int timeout, timer_id; + int timeout; - if (VIR_ALLOC(timer_info) < 0) { + if (VIR_ALLOC(info) < 0) { virReportOOMError(); return -1; } @@ -230,17 +249,17 @@ libxlTimeoutRegisterEventHook(void *priv, } else { timeout = res.tv_sec * 1000 + (res.tv_usec + 999) / 1000; } - timer_id = virEventAddTimeout(timeout, libxlTimerCallback, - timer_info, libxlTimerInfoFree); - if (timer_id < 0) { - VIR_FREE(timer_info); - return timer_id; + info->id = virEventAddTimeout(timeout, libxlTimerCallback, + info, libxlEventHookInfoFree); + if (info->id < 0) { + VIR_FREE(info); + return -1; } - timer_info->priv = priv; - timer_info->xl_priv = xl_priv; - timer_info->id = timer_id; - *hndp = timer_info; + info->priv = priv; + info->xl_priv = xl_priv; + *hndp = info; + return 0; } @@ -259,10 +278,13 @@ libxlTimeoutModifyEventHook(void *priv ATTRIBUTE_UNUSED, void **hndp, struct timeval abs_t ATTRIBUTE_UNUSED) { - struct libxlOSEventHookTimerInfo *timer_info = *hndp; + libxlEventHookInfoPtr info = *hndp; + virObjectLock(info->priv); /* Make the timeout fire */ - virEventUpdateTimeout(timer_info->id, 0); + virEventUpdateTimeout(info->id, 0); + virObjectUnlock(info->priv); + return 0; } @@ -270,9 +292,12 @@ static void libxlTimeoutDeregisterEventHook(void *priv ATTRIBUTE_UNUSED, void *hnd) { - struct libxlOSEventHookTimerInfo *timer_info = hnd; + libxlEventHookInfoPtr info = hnd; + libxlDomainObjPrivatePtr p = info->priv; - virEventRemoveTimeout(timer_info->id); + virObjectLock(p); + virEventRemoveTimeout(info->id); + virObjectUnlock(p); } static const libxl_osevent_hooks libxl_event_callbacks = { @@ -289,12 +314,15 @@ libxlDomainObjPrivateAlloc(void) { libxlDomainObjPrivatePtr priv; - if (VIR_ALLOC(priv) < 0) + if (libxlDomainObjPrivateInitialize() < 0) + return NULL; + + if (!(priv = virObjectLockableNew(libxlDomainObjPrivateClass))) return NULL; if (libxl_ctx_alloc(&priv->ctx, LIBXL_VERSION, 0, libxl_driver->logger)) { VIR_ERROR(_("Failed libxl context initialization")); - VIR_FREE(priv); + virObjectUnref(priv); return NULL; } @@ -312,7 +340,7 @@ libxlDomainObjPrivateFree(void *data) libxl_evdisable_domain_death(priv->ctx, priv->deathW); libxl_ctx_free(priv->ctx); - VIR_FREE(priv); + virObjectUnref(priv); } /* driver must be locked before calling */