cfg80211: fix BSS struct IE access races
When a BSS struct is updated, the IEs are currently
overwritten or freed. This can lead to races if some
other CPU is accessing the BSS struct and using the
IEs concurrently.
Fix this by always allocating the IEs in a new struct
that holds the data and length and protecting access
to this new struct with RCU.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
diff --git a/net/wireless/nl80211.c b/net/wireless/nl80211.c
index 4a71977..f45706a 100644
--- a/net/wireless/nl80211.c
+++ b/net/wireless/nl80211.c
@@ -4808,6 +4808,7 @@
struct cfg80211_internal_bss *intbss)
{
struct cfg80211_bss *res = &intbss->pub;
+ const struct cfg80211_bss_ies *ies;
void *hdr;
struct nlattr *bss;
@@ -4828,16 +4829,24 @@
if (!bss)
goto nla_put_failure;
if ((!is_zero_ether_addr(res->bssid) &&
- nla_put(msg, NL80211_BSS_BSSID, ETH_ALEN, res->bssid)) ||
- (res->information_elements && res->len_information_elements &&
- nla_put(msg, NL80211_BSS_INFORMATION_ELEMENTS,
- res->len_information_elements,
- res->information_elements)) ||
- (res->beacon_ies && res->len_beacon_ies &&
- res->beacon_ies != res->information_elements &&
- nla_put(msg, NL80211_BSS_BEACON_IES,
- res->len_beacon_ies, res->beacon_ies)))
+ nla_put(msg, NL80211_BSS_BSSID, ETH_ALEN, res->bssid)))
goto nla_put_failure;
+
+ rcu_read_lock();
+ ies = rcu_dereference(res->ies);
+ if (ies && ies->len && nla_put(msg, NL80211_BSS_INFORMATION_ELEMENTS,
+ ies->len, ies->data)) {
+ rcu_read_unlock();
+ goto nla_put_failure;
+ }
+ ies = rcu_dereference(res->beacon_ies);
+ if (ies && ies->len && nla_put(msg, NL80211_BSS_BEACON_IES,
+ ies->len, ies->data)) {
+ rcu_read_unlock();
+ goto nla_put_failure;
+ }
+ rcu_read_unlock();
+
if (res->tsf &&
nla_put_u64(msg, NL80211_BSS_TSF, res->tsf))
goto nla_put_failure;