git: 32af70fae827 - main - net80211: make sure to not start a BGSCAN if not enabled

The branch main has been updated by bz:

URL: https://cgit.FreeBSD.org/src/commit/?id=32af70fae827ecab34e995b49ea7656ea6e70608

commit 32af70fae827ecab34e995b49ea7656ea6e70608
Author:     Bjoern A. Zeeb <bz@FreeBSD.org>
AuthorDate: 2025-05-24 17:01:59 +0000
Commit:     Bjoern A. Zeeb <bz@FreeBSD.org>
CommitDate: 2025-05-28 10:42:58 +0000

    net80211: make sure to not start a BGSCAN if not enabled
    
    On drivers not supporting background scanning (not having announced
    IEEE80211_C_BGSCAN) we repeatedly have seen scanning issues and
    BGSCAN was "on" according to, e.g., ddb show com /a.
    
    Turns out there are multiple problems:
    (a) the ioctl scanreq code can pass IEEE80211_[IOC_]SCAN_BGSCAN in
        (ifconfig wlanX scan will do so by default).  That flag ends up
        on flags in the scanning code which have no other checks, and
        we are doing a BGSCAN.
        So make sure BGSCAN is announced by the driver and enabled
        (and it's STA mode for the full check) or filter the BGSCAN out.
    
    (b) ieee80211_bg_scan() never checked if background scanning was
        available/enabled.  Do so now.
    
    (c) ieee80211_swscan_start_scan_locked() as a consequence of (a) would
        start the BGSCAN unconditionally.  Also check for BGSCAN to be
        available/enabled here.
    
    Lastly, we should no longer reach ieee80211_swscan_bg_scan() without
    background scanning being available/enabled, so document that fact
    by placing a KASSERT.  That will also help in case future changes
    will open a new hole or there are further which I have not noticed.
    
    Sponsored by:   The FreeBSD Foundation
    MFC after:      3 days
    Reviewed by:    adrian
    Differential Revision: https://reviews.freebsd.org/D50513
---
 sys/net80211/ieee80211_ioctl.c   | 12 ++++++++++++
 sys/net80211/ieee80211_scan.c    | 13 +++++++++++++
 sys/net80211/ieee80211_scan_sw.c |  8 +++++++-
 3 files changed, 32 insertions(+), 1 deletion(-)

diff --git a/sys/net80211/ieee80211_ioctl.c b/sys/net80211/ieee80211_ioctl.c
index a72568e559aa..85d46c018d36 100644
--- a/sys/net80211/ieee80211_ioctl.c
+++ b/sys/net80211/ieee80211_ioctl.c
@@ -2598,6 +2598,18 @@ ieee80211_scanreq(struct ieee80211vap *vap, struct ieee80211_scan_req *sr)
 			return EINVAL;
 	/* cleanse flags just in case, could reject if invalid flags */
 	sr->sr_flags &= IEEE80211_IOC_SCAN_FLAGS;
+
+	/*
+	 * If the driver does not support BGSCAN, or BGSCAN is disabled
+	 * do not allow the IEEE80211_SCAN_BGSCAN flag to go through
+	 * to avoid accidentally enabling BGSCANs.
+	 * Also if not STA mode [see ieee80211_vap_setup()].
+	 */
+	if ((vap->iv_caps & IEEE80211_C_BGSCAN) == 0 ||
+	    (vap->iv_flags & IEEE80211_F_BGSCAN) == 0 ||
+	    vap->iv_opmode != IEEE80211_M_STA)
+		sr->sr_flags &= ~IEEE80211_IOC_SCAN_BGSCAN;
+
 	/*
 	 * Add an implicit NOPICK if the vap is not marked UP.  This
 	 * allows applications to scan without joining a bss (or picking
diff --git a/sys/net80211/ieee80211_scan.c b/sys/net80211/ieee80211_scan.c
index 02cad610ee8e..f77baac1b134 100644
--- a/sys/net80211/ieee80211_scan.c
+++ b/sys/net80211/ieee80211_scan.c
@@ -428,6 +428,19 @@ ieee80211_bg_scan(struct ieee80211vap *vap, int flags)
 
 	// IEEE80211_UNLOCK_ASSERT(sc);
 
+	/*
+	 * If the driver has not announced BGSCAN capabilities
+	 * or BGSCAN is disabled do not attempt to start a bg_scan.
+	 * IEEE80211_F_BGSCAN only gets set if IEEE80211_C_BGSCAN
+	 * was set by the driver, so no need to check for both here.
+	 */
+	if ((vap->iv_flags & IEEE80211_F_BGSCAN) == 0) {
+		IEEE80211_DPRINTF(vap, IEEE80211_MSG_SCAN,
+		    "%s: BGSCAN not enabled; not starting bg_scan\n",
+		    __func__);
+		return (0);
+	}
+
 	scan = ieee80211_scanner_get(vap->iv_opmode);
 	if (scan == NULL) {
 		IEEE80211_DPRINTF(vap, IEEE80211_MSG_SCAN,
diff --git a/sys/net80211/ieee80211_scan_sw.c b/sys/net80211/ieee80211_scan_sw.c
index f64730ce852f..d5770ff41968 100644
--- a/sys/net80211/ieee80211_scan_sw.c
+++ b/sys/net80211/ieee80211_scan_sw.c
@@ -201,7 +201,9 @@ ieee80211_swscan_start_scan_locked(const struct ieee80211_scanner *scan,
 				vap->iv_stats.is_scan_passive++;
 			if (flags & IEEE80211_SCAN_FLUSH)
 				ss->ss_ops->scan_flush(ss);
-			if (flags & IEEE80211_SCAN_BGSCAN)
+			/* Only BGSCAN if enabled and requested. */
+			if ((vap->iv_flags & IEEE80211_F_BGSCAN) != 0 &&
+			    (flags & IEEE80211_SCAN_BGSCAN) != 0)
 				ic->ic_flags_ext |= IEEE80211_FEXT_BGSCAN;
 
 			/* Set duration for this particular scan */
@@ -339,6 +341,10 @@ ieee80211_swscan_bg_scan(const struct ieee80211_scanner *scan,
 	// IEEE80211_UNLOCK_ASSERT(ic);
 
 	IEEE80211_LOCK(ic);
+	KASSERT((vap->iv_flags & IEEE80211_F_BGSCAN) != 0,
+	    ("%s: vap %p iv_flags %#010x no IEEE80211_F_BGSCAN set",
+	    __func__, vap, vap->iv_flags));
+
 	scanning = ic->ic_flags & IEEE80211_F_SCAN;
 	if (!scanning) {
 		u_int duration;