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scan: refactor start_next_scan_request to not send duplicate requests

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If start_scan_next_request() is called while a scan request
(NL80211_CMD_TRIGGER_SCAN) is still running, the same scan request will
be sent again. Add a check in the function to avoid sending a request if
one is already in progress. For consistency, check also that scan
results are not being requested (NL80211_CMD_GET_SCAN), before trying to
send the next scan request. Finally, remove similar checks at
start_next_scan_request() callsites to simplify the code.

This also fixes a crash that occurs if the following conditions are met:
  - the duplicated request is the only request in the scan request
    queue, and
  - both scan requests fail with an error not EBUSY.

In this case, the first callback to scan_request_triggered() will delete
the request from the scan request queue. The second callback will find
an empty queue and consequently pass a NULL scan_request pointer to
scan_request_failed(), causing a segmentation fault.
This commit is contained in:
Alvin Šipraga 2020-06-08 10:42:07 +02:00 committed by Denis Kenzior
parent 5c7f064f26
commit 8db4d9272a
1 changed files with 5 additions and 2 deletions
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7
src/scan.c
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@ -842,6 +842,9 @@ static bool start_next_scan_request(struct scan_context *sc)
if (sc->state != SCAN_STATE_NOT_RUNNING)
return true;
if (sc->start_cmd_id || sc->get_scan_cmd_id)
return true;
while (sr) {
if (!scan_request_send_trigger(sc, sr))
return true;
@ -1668,7 +1671,7 @@ static void scan_notify(struct l_genl_msg *msg, void *user_data)
/* An external scan may have flushed our results */
if (sc->started && scan_parse_flush_flag_from_msg(msg))
scan_finished(sc, -EAGAIN, NULL, sr);
else if (sr && !sc->start_cmd_id)
else
send_next = true;
sr = NULL;
@ -1719,7 +1722,7 @@ static void scan_notify(struct l_genl_msg *msg, void *user_data)
sc->triggered = false;
scan_finished(sc, -ECANCELED, NULL, sr);
} else if (sr && !sc->start_cmd_id && !sc->get_scan_cmd_id) {
} else {
/*
* If this was an external scan that got aborted
* we may be able to now queue our own scan although