Before v4.15 commit 75492a51568b ("s390/scsi: Convert timers to use
timer_setup()"), we intentionally only passed zfcp_adapter as context
argument to zfcp_fsf_request_timeout_handler(). Since we only trigger
adapter recovery, it was unnecessary to sync against races between timeout
and (late) completion.
Likewise, we only passed zfcp_erp_action as context argument to
zfcp_erp_timeout_handler(). Since we only wakeup an ERP action, it was
unnecessary to sync against races between timeout and (late) completion.
Meanwhile the timeout handlers get timer_list as context argument
and do a timer-specific container-of to zfcp_fsf_req which can have
been freed.
Fix it by making sure that any request timeout handlers, that might
just have started before del_timer(), are completed by using
del_timer_sync() instead. This ensures the request free happens
afterwards.
Space time diagram of potential use-after-free:
Basic idea is to have 2 or more pending requests whose timeouts run
out at almost the same time.
req 1 timeout ERP thread req 2 timeout
---------------- ---------------- ---------------------------------------
zfcp_fsf_request_timeout_handler
fsf_req = from_timer(fsf_req, t, timer)
adapter = fsf_req->adapter
zfcp_qdio_siosl(adapter)
zfcp_erp_adapter_reopen(adapter,...)
zfcp_erp_strategy
...
zfcp_fsf_req_dismiss_all
list_for_each_entry_safe
zfcp_fsf_req_complete 1
del_timer 1
zfcp_fsf_req_free 1
zfcp_fsf_req_complete 2
zfcp_fsf_request_timeout_handler
del_timer 2
fsf_req = from_timer(fsf_req, t, timer)
zfcp_fsf_req_free 2
adapter = fsf_req->adapter
^^^^^^^ already freed
Suggested-by: Julian Wiedmann <jwi@xxxxxxxxxxxxx>
Reviewed-by: Julian Wiedmann <jwi@xxxxxxxxxxxxx>
Fixes: 75492a51568b ("s390/scsi: Convert timers to use timer_setup()")
Cc: <stable@xxxxxxxxxxxxxxx> #4.15+
Signed-off-by: Steffen Maier <maier@xxxxxxxxxxxxx>
---
drivers/s390/scsi/zfcp_fsf.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/s390/scsi/zfcp_fsf.c b/drivers/s390/scsi/zfcp_fsf.c
index c795f22249d8..140186fe1d1e 100644
--- a/drivers/s390/scsi/zfcp_fsf.c
+++ b/drivers/s390/scsi/zfcp_fsf.c
@@ -434,7 +434,7 @@ static void zfcp_fsf_req_complete(struct zfcp_fsf_req *req)
return;
}
- del_timer(&req->timer);
+ del_timer_sync(&req->timer);
zfcp_fsf_protstatus_eval(req);
zfcp_fsf_fsfstatus_eval(req);
req->handler(req);
@@ -867,7 +867,7 @@ static int zfcp_fsf_req_send(struct zfcp_fsf_req *req)
req->qdio_req.qdio_outb_usage = atomic_read(&qdio->req_q_free);
req->issued = get_tod_clock();
if (zfcp_qdio_send(qdio, &req->qdio_req)) {
- del_timer(&req->timer);
+ del_timer_sync(&req->timer);
/* lookup request again, list might have changed */
zfcp_reqlist_find_rm(adapter->req_list, req_id);
zfcp_erp_adapter_reopen(adapter, 0, "fsrs__1");
--
2.17.1
