From bfe29873454f38eb1a511a76144ad1a4848ca176 Mon Sep 17 00:00:00 2001 From: Johannes Berg Date: Fri, 30 Sep 2022 23:44:23 +0200 Subject: [PATCH] wifi: cfg80211: fix BSS refcounting bugs MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit commit 0b7808818cb9df6680f98996b8e9a439fa7bcc2f upstream. There are multiple refcounting bugs related to multi-BSSID: - In bss_ref_get(), if the BSS has a hidden_beacon_bss, then the bss pointer is overwritten before checking for the transmitted BSS, which is clearly wrong. Fix this by using the bss_from_pub() macro. - In cfg80211_bss_update() we copy the transmitted_bss pointer from tmp into new, but then if we release new, we'll unref it erroneously. We already set the pointer and ref it, but need to NULL it since it was copied from the tmp data. - In cfg80211_inform_single_bss_data(), if adding to the non- transmitted list fails, we unlink the BSS and yet still we return it, but this results in returning an entry without a reference. We shouldn't return it anyway if it was broken enough to not get added there. This fixes CVE-2022-42720. Reported-by: Sönke Huster Tested-by: Sönke Huster Fixes: a3584f56de1c ("cfg80211: Properly track transmitting and non-transmitting BSS") Signed-off-by: Johannes Berg Signed-off-by: Greg Kroah-Hartman --- net/wireless/scan.c | 27 ++++++++++++++------------- 1 file changed, 14 insertions(+), 13 deletions(-) diff --git a/net/wireless/scan.c b/net/wireless/scan.c index 04c9b78..2e57671 100644 --- a/net/wireless/scan.c +++ b/net/wireless/scan.c @@ -143,18 +143,12 @@ static inline void bss_ref_get(struct cfg80211_registered_device *rdev, lockdep_assert_held(&rdev->bss_lock); bss->refcount++; - if (bss->pub.hidden_beacon_bss) { - bss = container_of(bss->pub.hidden_beacon_bss, - struct cfg80211_internal_bss, - pub); - bss->refcount++; - } - if (bss->pub.transmitted_bss) { - bss = container_of(bss->pub.transmitted_bss, - struct cfg80211_internal_bss, - pub); - bss->refcount++; - } + + if (bss->pub.hidden_beacon_bss) + bss_from_pub(bss->pub.hidden_beacon_bss)->refcount++; + + if (bss->pub.transmitted_bss) + bss_from_pub(bss->pub.transmitted_bss)->refcount++; } static inline void bss_ref_put(struct cfg80211_registered_device *rdev, @@ -1743,6 +1737,8 @@ cfg80211_bss_update(struct cfg80211_registered_device *rdev, new->refcount = 1; INIT_LIST_HEAD(&new->hidden_list); INIT_LIST_HEAD(&new->pub.nontrans_list); + /* we'll set this later if it was non-NULL */ + new->pub.transmitted_bss = NULL; if (rcu_access_pointer(tmp->pub.proberesp_ies)) { hidden = rb_find_bss(rdev, tmp, BSS_CMP_HIDE_ZLEN); @@ -1983,10 +1979,15 @@ cfg80211_inform_single_bss_data(struct wiphy *wiphy, spin_lock_bh(&rdev->bss_lock); if (cfg80211_add_nontrans_list(non_tx_data->tx_bss, &res->pub)) { - if (__cfg80211_unlink_bss(rdev, res)) + if (__cfg80211_unlink_bss(rdev, res)) { rdev->bss_generation++; + res = NULL; + } } spin_unlock_bh(&rdev->bss_lock); + + if (!res) + return NULL; } trace_cfg80211_return_bss(&res->pub); -- 2.7.4