From 3d1b5d3c4da7426dcc11ae9a9ea1247dec255bfb Mon Sep 17 00:00:00 2001 From: Karsten Graul Date: Wed, 14 Oct 2020 19:43:27 +0200 Subject: [PATCH] net/smc: fix use-after-free of delayed events [ Upstream commit d535ca1367787ddc8bff22d679a11f864c8228bc ] When a delayed event is enqueued then the event worker will send this event the next time it is running and no other flow is currently active. The event handler is called for the delayed event, and the pointer to the event keeps set in lgr->delayed_event. This pointer is cleared later in the processing by smc_llc_flow_start(). This can lead to a use-after-free condition when the processing does not reach smc_llc_flow_start(), but frees the event because of an error situation. Then the delayed_event pointer is still set but the event is freed. Fix this by always clearing the delayed event pointer when the event is provided to the event handler for processing, and remove the code to clear it in smc_llc_flow_start(). Fixes: 555da9af827d ("net/smc: add event-based llc_flow framework") Signed-off-by: Karsten Graul Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman --- net/smc/smc_llc.c | 13 +++++-------- 1 file changed, 5 insertions(+), 8 deletions(-) diff --git a/net/smc/smc_llc.c b/net/smc/smc_llc.c index 3ea33466ebe98..da9332de26c5d 100644 --- a/net/smc/smc_llc.c +++ b/net/smc/smc_llc.c @@ -233,8 +233,6 @@ static bool smc_llc_flow_start(struct smc_llc_flow *flow, default: flow->type = SMC_LLC_FLOW_NONE; } - if (qentry == lgr->delayed_event) - lgr->delayed_event = NULL; smc_llc_flow_qentry_set(flow, qentry); spin_unlock_bh(&lgr->llc_flow_lock); return true; @@ -1603,13 +1601,12 @@ static void smc_llc_event_work(struct work_struct *work) struct smc_llc_qentry *qentry; if (!lgr->llc_flow_lcl.type && lgr->delayed_event) { - if (smc_link_usable(lgr->delayed_event->link)) { - smc_llc_event_handler(lgr->delayed_event); - } else { - qentry = lgr->delayed_event; - lgr->delayed_event = NULL; + qentry = lgr->delayed_event; + lgr->delayed_event = NULL; + if (smc_link_usable(qentry->link)) + smc_llc_event_handler(qentry); + else kfree(qentry); - } } again: -- 2.51.0