[RFC,v5.4,3/3] wifi: mac80211: fix MBSSID parsing use-after-free

Commit Message

Johannes Berg Oct. 14, 2022, 4:47 p.m. UTC

From: Johannes Berg <[e-mail]>

Commit ff05d4b45dd89b922578dac497dcabf57cf771c6 upstream.
This is a different version of the commit, changed to store
the non-transmitted profile in the elems, and freeing it in
the few places where it's relevant, since that is only the
case when the last argument for parsing (the non-tx BSSID)
is non-NULL.

When we parse a multi-BSSID element, we might point some
element pointers into the allocated nontransmitted_profile.
However, we free this before returning, causing UAF when the
relevant pointers in the parsed elements are accessed.

Fix this by not allocating the scratch buffer separately but
as part of the returned structure instead, that way, there
are no lifetime issues with it.

The scratch buffer introduction as part of the returned data
here is taken from MLO feature work done by Ilan.

This fixes CVE-2022-42719.

Fixes: 5023b14cf4df ("mac80211: support profile split between elements")
Co-developed-by: Ilan Peer <[e-mail]>
Signed-off-by: Ilan Peer <[e-mail]>
Reviewed-by: Kees Cook <[e-mail]>
Signed-off-by: Johannes Berg <[e-mail]>
---
 net/mac80211/ieee80211_i.h | 2 ++
 net/mac80211/mlme.c        | 6 +++++-
 net/mac80211/scan.c        | 2 ++
 net/mac80211/util.c        | 7 ++++++-
 4 files changed, 15 insertions(+), 2 deletions(-)

Patch

diff --git a/net/mac80211/ieee80211_i.h b/net/mac80211/ieee80211_i.h
index 3d5da7a97be4..f30a205323de 100644
--- a/net/mac80211/ieee80211_i.h
+++ b/net/mac80211/ieee80211_i.h
@@ -1519,6 +1519,8 @@  struct ieee802_11_elems {
 	u8 country_elem_len;
 	u8 bssid_index_len;
 
+	void *nontx_profile;
+
 	/* whether a parse error occurred while retrieving these elements */
 	bool parse_error;
 };
diff --git a/net/mac80211/mlme.c b/net/mac80211/mlme.c
index 7d116aa4ea1f..b48a09043663 100644
--- a/net/mac80211/mlme.c
+++ b/net/mac80211/mlme.c
@@ -3299,6 +3299,7 @@  static bool ieee80211_assoc_success(struct ieee80211_sub_if_data *sdata,
 			sdata_info(sdata,
 				   "AP bug: VHT operation missing from AssocResp\n");
 		}
+		kfree(bss_elems.nontx_profile);
 	}
 
 	/*
@@ -3883,6 +3884,7 @@  static void ieee80211_rx_mgmt_beacon(struct ieee80211_sub_if_data *sdata,
 		ifmgd->assoc_data->timeout = jiffies;
 		ifmgd->assoc_data->timeout_started = true;
 		run_again(sdata, ifmgd->assoc_data->timeout);
+		kfree(elems.nontx_profile);
 		return;
 	}
 
@@ -4050,7 +4052,7 @@  static void ieee80211_rx_mgmt_beacon(struct ieee80211_sub_if_data *sdata,
 		ieee80211_report_disconnect(sdata, deauth_buf,
 					    sizeof(deauth_buf), true,
 					    WLAN_REASON_DEAUTH_LEAVING);
-		return;
+		goto free;
 	}
 
 	if (sta && elems.opmode_notif)
@@ -4065,6 +4067,8 @@  static void ieee80211_rx_mgmt_beacon(struct ieee80211_sub_if_data *sdata,
 					       elems.cisco_dtpc_elem);
 
 	ieee80211_bss_info_change_notify(sdata, changed);
+free:
+	kfree(elems.nontx_profile);
 }
 
 void ieee80211_sta_rx_queued_mgmt(struct ieee80211_sub_if_data *sdata,
diff --git a/net/mac80211/scan.c b/net/mac80211/scan.c
index c353162e81ae..ee65f1f50a0a 100644
--- a/net/mac80211/scan.c
+++ b/net/mac80211/scan.c
@@ -216,6 +216,8 @@  ieee80211_bss_info_update(struct ieee80211_local *local,
 						rx_status, beacon);
 	}
 
+	kfree(elems.nontx_profile);
+
 	return bss;
 }
 
diff --git a/net/mac80211/util.c b/net/mac80211/util.c
index 1ba37f67a2a0..6223af1c3457 100644
--- a/net/mac80211/util.c
+++ b/net/mac80211/util.c
@@ -1363,6 +1363,11 @@  u32 ieee802_11_parse_elems_crc(const u8 *start, size_t len, bool action,
 			cfg80211_find_ext_elem(WLAN_EID_EXT_NON_INHERITANCE,
 					       nontransmitted_profile,
 					       nontransmitted_profile_len);
+		if (!nontransmitted_profile_len) {
+			nontransmitted_profile_len = 0;
+			kfree(nontransmitted_profile);
+			nontransmitted_profile = NULL;
+		}
 	}
 
 	crc = _ieee802_11_parse_elems_crc(start, len, action, elems, filter,
@@ -1392,7 +1397,7 @@  u32 ieee802_11_parse_elems_crc(const u8 *start, size_t len, bool action,
 	    offsetofend(struct ieee80211_bssid_index, dtim_count))
 		elems->dtim_count = elems->bssid_index->dtim_count;
 
-	kfree(nontransmitted_profile);
+	elems->nontx_profile = nontransmitted_profile;
 
 	return crc;
 }