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 48fbccbf2a545a5b09a5b50448f5f3df50570558..44c8701af95c034e96ac50e3a3944613595c556f 100644 (file)
--- a/net/mac80211/ieee80211_i.h
+++ b/net/mac80211/ieee80211_i.h
@@ -1640,6 +1640,14 @@ 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 504422cc683e9ccd29a0604a260bd3b840c24cd8..8f36ab8fcfb245dd5c3bc59e2ef1c06a567e57c2 100644 (file)
--- a/net/mac80211/util.c
+++ b/net/mac80211/util.c
@@ -1503,25 +1503,27 @@ struct ieee802_11_elems *ieee802_11_parse_elems_crc(const u8 *start, size_t len,
        const struct element *non_inherit = NULL;
        u8 *nontransmitted_profile;
        int nontransmitted_profile_len = 0;
+       size_t scratch_len = len;
 
-       elems = kzalloc(sizeof(*elems), GFP_ATOMIC);
+       elems = kzalloc(sizeof(*elems) + scratch_len, GFP_ATOMIC);
        if (!elems)
                return NULL;
        elems->ie_start = start;
        elems->total_len = len;
-
-       nontransmitted_profile = kmalloc(len, GFP_ATOMIC);
-       if (nontransmitted_profile) {
-               nontransmitted_profile_len =
-                       ieee802_11_find_bssid_profile(start, len, elems,
-                                                     transmitter_bssid,
-                                                     bss_bssid,
-                                                     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(start, len, elems,
+                                             transmitter_bssid,
+                                             bss_bssid,
+                                             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);
 
        crc = _ieee802_11_parse_elems_crc(start, len, action, elems, filter,
                                          crc, non_inherit);
@@ -1550,8 +1552,6 @@ struct ieee802_11_elems *ieee802_11_parse_elems_crc(const u8 *start, size_t len,
            offsetofend(struct ieee80211_bssid_index, dtim_count))
                elems->dtim_count = elems->bssid_index->dtim_count;
 
-       kfree(nontransmitted_profile);
-
        elems->crc = crc;
 
        return elems;