libmultipath: update waiter handling

The current 'waiter' structure accesses fields which belong
to the main 'mpp' structure, which has a totally different
lifetime. With this patch most of these dependencies are
removed and the 'waiter' structure can run independently
of the main 'mpp' structure, reducing the risk of
use-after-free faults.

Signed-off-by: Hannes Reinecke <hare@suse.de>

diff --git a/libmultipath/structs.c b/libmultipath/structs.c
index d482b4c..280d2eb 100644 (file)
--- a/libmultipath/structs.c
+++ b/libmultipath/structs.c
@@ -15,7 +15,6 @@
 #include "debug.h"
 #include "structs_vec.h"
 #include "blacklist.h"
-#include "waiter.h"
 #include "prio.h"
 
 struct path *
@@ -172,12 +171,6 @@ free_multipath (struct multipath * mpp, enum free_path_mode free_paths)
                mpp->dmi = NULL;
        }
 
-       /*
-        * better own vecs->lock here
-        */
-       if (mpp->waiter)
-               ((struct event_thread *)mpp->waiter)->mpp = NULL;
-
        free_pathvec(mpp->paths, free_paths);
        free_pgvec(mpp->pg, free_paths);
        FREE_PTR(mpp->mpcontext);

diff --git a/libmultipath/structs.h b/libmultipath/structs.h
index 070f2fe..0afa340 100644 (file)
--- a/libmultipath/structs.h
+++ b/libmultipath/structs.h
@@ -4,9 +4,9 @@
 #include <sys/types.h>
 
 #define WWID_SIZE              128
-#define SERIAL_SIZE            64
-#define NODE_NAME_SIZE         19
-#define PATH_STR_SIZE                  16
+#define SERIAL_SIZE            65
+#define NODE_NAME_SIZE         65
+#define PATH_STR_SIZE          16
 #define PARAMS_SIZE            1024
 #define FILE_NAME_SIZE         256
 #define CALLOUT_MAX_SIZE       256

diff --git a/libmultipath/waiter.c b/libmultipath/waiter.c
index 4fb2cff..0be5d21 100644 (file)
--- a/libmultipath/waiter.c
+++ b/libmultipath/waiter.c
@@ -28,38 +28,24 @@ struct event_thread *alloc_waiter (void)
        struct event_thread *wp;
 
        wp = (struct event_thread *)MALLOC(sizeof(struct event_thread));
+       memset(wp, 0, sizeof(struct event_thread));
+       pthread_mutex_init(&wp->lock, NULL);
 
        return wp;
 }
 
-void free_waiter (void *data)
+void signal_waiter (void *data)
 {
-       sigset_t old;
        struct event_thread *wp = (struct event_thread *)data;
 
-       /*
-        * indicate in mpp that the wp is already freed storage
-        */
-       block_signal(SIGHUP, &old);
-       lock(wp->vecs->lock);
-
-       if (wp->mpp)
-               /*
-                * be careful, mpp may already be freed -- null if so
-                */
-               wp->mpp->waiter = NULL;
-       else
-               /*
-               * This is OK condition during shutdown.
-               */
-               condlog(3, "free_waiter, mpp freed before wp=%p (%s).", wp, wp->mapname);
-
-       unlock(wp->vecs->lock);
-       pthread_sigmask(SIG_SETMASK, &old, NULL);
-
-       if (wp->dmt)
-               dm_task_destroy(wp->dmt);
+       pthread_mutex_lock(&wp->lock);
+       memset(wp->mapname, 0, WWID_SIZE);
+       pthread_mutex_unlock(&wp->lock);
+}
 
+void free_waiter (struct event_thread *wp)
+{
+       pthread_mutex_destroy(&wp->lock);
        FREE(wp);
 }
 
@@ -72,9 +58,16 @@ void stop_waiter_thread (struct multipath *mpp, struct vectors *vecs)
                condlog(3, "%s: no waiter thread", mpp->alias);
                return;
        }
+       if (wp->thread == (pthread_t)0) {
+               condlog(3, "%s: event checker thread already stopped",
+                       mpp->alias);
+               return;
+       }
        thread = wp->thread;
-       condlog(2, "%s: stop event checker thread (%lu)", wp->mapname, thread);
+       wp->thread = (pthread_t)0;
+       mpp->waiter = NULL;
 
+       condlog(2, "%s: stop event checker thread (%lu)", wp->mapname, thread);
        pthread_kill(thread, SIGUSR1);
 }
 
@@ -96,49 +89,61 @@ static sigset_t unblock_signals(void)
 int waiteventloop (struct event_thread *waiter)
 {
        sigset_t set;
+       struct dm_task *dmt = NULL;
        int event_nr;
        int r;
 
+       pthread_mutex_lock(&waiter->lock);
        if (!waiter->event_nr)
                waiter->event_nr = dm_geteventnr(waiter->mapname);
 
-       if (!(waiter->dmt = dm_task_create(DM_DEVICE_WAITEVENT))) {
+       if (!(dmt = dm_task_create(DM_DEVICE_WAITEVENT))) {
                condlog(0, "%s: devmap event #%i dm_task_create error",
                                waiter->mapname, waiter->event_nr);
+               pthread_mutex_unlock(&waiter->lock);
                return 1;
        }
 
-       if (!dm_task_set_name(waiter->dmt, waiter->mapname)) {
+       if (!dm_task_set_name(dmt, waiter->mapname)) {
                condlog(0, "%s: devmap event #%i dm_task_set_name error",
                                waiter->mapname, waiter->event_nr);
-               dm_task_destroy(waiter->dmt);
+               dm_task_destroy(dmt);
+               pthread_mutex_unlock(&waiter->lock);
                return 1;
        }
 
-       if (waiter->event_nr && !dm_task_set_event_nr(waiter->dmt,
+       if (waiter->event_nr && !dm_task_set_event_nr(dmt,
                                                      waiter->event_nr)) {
                condlog(0, "%s: devmap event #%i dm_task_set_event_nr error",
                                waiter->mapname, waiter->event_nr);
-               dm_task_destroy(waiter->dmt);
+               dm_task_destroy(dmt);
+               pthread_mutex_unlock(&waiter->lock);
                return 1;
        }
+       pthread_mutex_unlock(&waiter->lock);
 
-       dm_task_no_open_count(waiter->dmt);
+       dm_task_no_open_count(dmt);
 
        /* accept wait interruption */
        set = unblock_signals();
 
        /* wait */
-       r = dm_task_run(waiter->dmt);
+       r = dm_task_run(dmt);
 
        /* wait is over : event or interrupt */
        pthread_sigmask(SIG_SETMASK, &set, NULL);
 
-       if (!r) /* wait interrupted by signal */
+       dm_task_destroy(dmt);
+
+       if (!r) /* wait interrupted by signal */
                return -1;
 
-       dm_task_destroy(waiter->dmt);
-       waiter->dmt = NULL;
+       pthread_mutex_lock(&waiter->lock);
+       if (!strlen(waiter->mapname)) {
+               /* waiter should exit */
+               pthread_mutex_unlock(&waiter->lock);
+               return -1;
+       }
        waiter->event_nr++;
 
        /*
@@ -167,16 +172,20 @@ int waiteventloop (struct event_thread *waiter)
                if (r) {
                        condlog(2, "%s: event checker exit",
                                waiter->mapname);
+                       pthread_mutex_unlock(&waiter->lock);
                        return -1; /* stop the thread */
                }
 
                event_nr = dm_geteventnr(waiter->mapname);
 
-               if (waiter->event_nr == event_nr)
+               if (waiter->event_nr == event_nr) {
+                       pthread_mutex_unlock(&waiter->lock);
                        return 1; /* upon problem reschedule 1s later */
+               }
 
                waiter->event_nr = event_nr;
        }
+       pthread_mutex_unlock(&waiter->lock);
        return -1; /* never reach there */
 }
 
@@ -188,7 +197,7 @@ void *waitevent (void *et)
        mlockall(MCL_CURRENT | MCL_FUTURE);
 
        waiter = (struct event_thread *)et;
-       pthread_cleanup_push(free_waiter, et);
+       pthread_cleanup_push(signal_waiter, et);
 
        block_signal(SIGUSR1, NULL);
        block_signal(SIGHUP, NULL);
@@ -202,6 +211,7 @@ void *waitevent (void *et)
        }
 
        pthread_cleanup_pop(1);
+       free_waiter(waiter);
        return NULL;
 }
 
@@ -217,10 +227,11 @@ int start_waiter_thread (struct multipath *mpp, struct vectors *vecs)
        if (!wp)
                goto out;
 
+       pthread_mutex_lock(&wp->lock);
        mpp->waiter = (void *)wp;
        strncpy(wp->mapname, mpp->alias, WWID_SIZE);
        wp->vecs = vecs;
-       wp->mpp = mpp;
+       pthread_mutex_unlock(&wp->lock);
 
        if (pthread_create(&wp->thread, &waiter_attr, waitevent, wp)) {
                condlog(0, "%s: cannot create event checker", wp->mapname);

diff --git a/libmultipath/waiter.h b/libmultipath/waiter.h
index ab362d1..28a6974 100644 (file)
--- a/libmultipath/waiter.h
+++ b/libmultipath/waiter.h
@@ -4,16 +4,15 @@
 extern pthread_attr_t waiter_attr;
 
 struct event_thread {
-       struct dm_task *dmt;
        pthread_t thread;
+       pthread_mutex_t lock;
        int event_nr;
        char mapname[WWID_SIZE];
        struct vectors *vecs;
-       struct multipath *mpp;
 };
 
 struct event_thread * alloc_waiter (void);
-void free_waiter (void *data);
+void signal_waiter (void *data);
 void stop_waiter_thread (struct multipath *mpp, struct vectors *vecs);
 int start_waiter_thread (struct multipath *mpp, struct vectors *vecs);
 int waiteventloop (struct event_thread *waiter);