From: Johannes Berg johannes.berg@intel.com
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 shuster@seemoo.tu-darmstadt.de Tested-by: Sönke Huster shuster@seemoo.tu-darmstadt.de Fixes: a3584f56de1c ("cfg80211: Properly track transmitting and non-transmitting BSS") Signed-off-by: Johannes Berg johannes.berg@intel.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/wireless/scan.c | 27 ++++++++++++++------------- 1 file changed, 14 insertions(+), 13 deletions(-)
--- a/net/wireless/scan.c +++ b/net/wireless/scan.c @@ -143,18 +143,12 @@ static inline void bss_ref_get(struct cf 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_regi 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 w 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);