From e8b35bf5dc8d4e98d91855a9c7b2ed905c8e6888 Mon Sep 17 00:00:00 2001 From: Roman Kagan Date: Thu, 10 Jun 2021 13:07:37 +0300 Subject: [PATCH] block/nbd: ensure ->connection_thread is always valid Simplify lifetime management of BDRVNBDState->connect_thread by delaying the possible cleanup of it until the BDRVNBDState itself goes away. This also reverts 0267101af6 "block/nbd: fix possible use after free of s->connect_thread" as now s->connect_thread can't be cleared until the very end. Signed-off-by: Roman Kagan [vsementsov: rebase, revert 0267101af6 changes] Signed-off-by: Vladimir Sementsov-Ogievskiy [eblake: tweak comment] Reviewed-by: Eric Blake Message-Id: <20210610100802.5888-8-vsementsov@virtuozzo.com> Signed-off-by: Eric Blake --- block/nbd.c | 56 ++++++++++++++++++++--------------------------------- 1 file changed, 21 insertions(+), 35 deletions(-) diff --git a/block/nbd.c b/block/nbd.c index 1c99654ef7..08ae47d83c 100644 --- a/block/nbd.c +++ b/block/nbd.c @@ -144,17 +144,31 @@ typedef struct BDRVNBDState { NBDConnectThread *connect_thread; } BDRVNBDState; +static void nbd_free_connect_thread(NBDConnectThread *thr); static int nbd_establish_connection(BlockDriverState *bs, SocketAddress *saddr, Error **errp); static int nbd_co_establish_connection(BlockDriverState *bs, Error **errp); -static void nbd_co_establish_connection_cancel(BlockDriverState *bs, - bool detach); +static void nbd_co_establish_connection_cancel(BlockDriverState *bs); static int nbd_client_handshake(BlockDriverState *bs, Error **errp); static void nbd_yank(void *opaque); static void nbd_clear_bdrvstate(BlockDriverState *bs) { BDRVNBDState *s = (BDRVNBDState *)bs->opaque; + NBDConnectThread *thr = s->connect_thread; + bool thr_running; + + qemu_mutex_lock(&thr->mutex); + thr_running = thr->state == CONNECT_THREAD_RUNNING; + if (thr_running) { + thr->state = CONNECT_THREAD_RUNNING_DETACHED; + } + qemu_mutex_unlock(&thr->mutex); + + /* the runaway thread will clean up itself */ + if (!thr_running) { + nbd_free_connect_thread(thr); + } yank_unregister_instance(BLOCKDEV_YANK_INSTANCE(bs->node_name)); @@ -295,7 +309,7 @@ static void coroutine_fn nbd_client_co_drain_begin(BlockDriverState *bs) s->drained = true; qemu_co_sleep_wake(&s->reconnect_sleep); - nbd_co_establish_connection_cancel(bs, false); + nbd_co_establish_connection_cancel(bs); reconnect_delay_timer_del(s); @@ -333,7 +347,7 @@ static void nbd_teardown_connection(BlockDriverState *bs) s->state = NBD_CLIENT_QUIT; if (s->connection_co) { qemu_co_sleep_wake(&s->reconnect_sleep); - nbd_co_establish_connection_cancel(bs, true); + nbd_co_establish_connection_cancel(bs); } if (qemu_in_coroutine()) { s->teardown_co = qemu_coroutine_self(); @@ -446,11 +460,6 @@ nbd_co_establish_connection(BlockDriverState *bs, Error **errp) BDRVNBDState *s = bs->opaque; NBDConnectThread *thr = s->connect_thread; - if (!thr) { - /* detached */ - return -1; - } - qemu_mutex_lock(&thr->mutex); switch (thr->state) { @@ -494,12 +503,6 @@ nbd_co_establish_connection(BlockDriverState *bs, Error **errp) s->wait_connect = true; qemu_coroutine_yield(); - if (!s->connect_thread) { - /* detached */ - return -1; - } - assert(thr == s->connect_thread); - qemu_mutex_lock(&thr->mutex); switch (thr->state) { @@ -547,18 +550,12 @@ nbd_co_establish_connection(BlockDriverState *bs, Error **errp) * nbd_co_establish_connection_cancel * Cancel nbd_co_establish_connection asynchronously: it will finish soon, to * allow drained section to begin. - * - * If detach is true, also cleanup the state (or if thread is running, move it - * to CONNECT_THREAD_RUNNING_DETACHED state). s->connect_thread becomes NULL if - * detach is true. */ -static void nbd_co_establish_connection_cancel(BlockDriverState *bs, - bool detach) +static void nbd_co_establish_connection_cancel(BlockDriverState *bs) { BDRVNBDState *s = bs->opaque; NBDConnectThread *thr = s->connect_thread; bool wake = false; - bool do_free = false; qemu_mutex_lock(&thr->mutex); @@ -569,21 +566,10 @@ static void nbd_co_establish_connection_cancel(BlockDriverState *bs, s->wait_connect = false; wake = true; } - if (detach) { - thr->state = CONNECT_THREAD_RUNNING_DETACHED; - s->connect_thread = NULL; - } - } else if (detach) { - do_free = true; } qemu_mutex_unlock(&thr->mutex); - if (do_free) { - nbd_free_connect_thread(thr); - s->connect_thread = NULL; - } - if (wake) { aio_co_wake(s->connection_co); } @@ -2310,6 +2296,8 @@ static int nbd_open(BlockDriverState *bs, QDict *options, int flags, goto fail; } + nbd_init_connect_thread(s); + /* * establish TCP connection, return error if it fails * TODO: Configurable retry-until-timeout behaviour. @@ -2326,8 +2314,6 @@ static int nbd_open(BlockDriverState *bs, QDict *options, int flags, /* successfully connected */ s->state = NBD_CLIENT_CONNECTED; - nbd_init_connect_thread(s); - s->connection_co = qemu_coroutine_create(nbd_connection_entry, s); bdrv_inc_in_flight(bs); aio_co_schedule(bdrv_get_aio_context(bs), s->connection_co);