wifi: mac80211: fix MBSSID parsing use-after-free

commit ff05d4b45dd89b922578dac497dcabf57cf771c6 upstream.

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 <ilan.peer@intel.com>
Signed-off-by: Ilan Peer <ilan.peer@intel.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/net/mac80211/ieee80211_i.h b/net/mac80211/ieee80211_i.h
index e192e1ec02610d2450513b2254cc56e1678ccb92..9583643b70332085cc6c493354c5ac4e7a0dcc50 100644 (file)
--- a/net/mac80211/ieee80211_i.h
+++ b/net/mac80211/ieee80211_i.h
@@ -1704,6 +1704,14 @@ struct ieee802_11_elems {
 
        /* whether a parse error occurred while retrieving these elements */
        bool parse_error;
+
+       /*
+        * scratch buffer that can be used for various element parsing related
+        * tasks, e.g., element de-fragmentation etc.
+        */
+       size_t scratch_len;
+       u8 *scratch_pos;
+       u8 scratch[];
 };
 
 static inline struct ieee80211_local *hw_to_local(

diff --git a/net/mac80211/util.c b/net/mac80211/util.c
index 3d097386b2b9a2234ef35c00481dbc8b8bb8486a..4fc3d545e6667cf2d4552b24c683434177c8c8e7 100644 (file)
--- a/net/mac80211/util.c
+++ b/net/mac80211/util.c
@@ -1503,24 +1503,26 @@ ieee802_11_parse_elems_full(struct ieee80211_elems_parse_params *params)
        const struct element *non_inherit = NULL;
        u8 *nontransmitted_profile;
        int nontransmitted_profile_len = 0;
+       size_t scratch_len = params->len;
 
-       elems = kzalloc(sizeof(*elems), GFP_ATOMIC);
+       elems = kzalloc(sizeof(*elems) + scratch_len, GFP_ATOMIC);
        if (!elems)
                return NULL;
        elems->ie_start = params->start;
        elems->total_len = params->len;
-
-       nontransmitted_profile = kmalloc(params->len, GFP_ATOMIC);
-       if (nontransmitted_profile) {
-               nontransmitted_profile_len =
-                       ieee802_11_find_bssid_profile(params->start, params->len,
-                                                     elems, params->bss,
-                                                     nontransmitted_profile);
-               non_inherit =
-                       cfg80211_find_ext_elem(WLAN_EID_EXT_NON_INHERITANCE,
-                                              nontransmitted_profile,
-                                              nontransmitted_profile_len);
-       }
+       elems->scratch_len = scratch_len;
+       elems->scratch_pos = elems->scratch;
+
+       nontransmitted_profile = elems->scratch_pos;
+       nontransmitted_profile_len =
+               ieee802_11_find_bssid_profile(params->start, params->len,
+                                             elems, params->bss,
+                                             nontransmitted_profile);
+       elems->scratch_pos += nontransmitted_profile_len;
+       elems->scratch_len -= nontransmitted_profile_len;
+       non_inherit = cfg80211_find_ext_elem(WLAN_EID_EXT_NON_INHERITANCE,
+                                            nontransmitted_profile,
+                                            nontransmitted_profile_len);
 
        elems->crc = _ieee802_11_parse_elems_full(params, elems, non_inherit);
 
@@ -1554,8 +1556,6 @@ ieee802_11_parse_elems_full(struct ieee80211_elems_parse_params *params)
            offsetofend(struct ieee80211_bssid_index, dtim_count))
                elems->dtim_count = elems->bssid_index->dtim_count;
 
-       kfree(nontransmitted_profile);
-
        return elems;
 }