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Subject[PATCH v3] nl80211: take RCU read lock when calling ieee80211_bss_get_ie()
As ieee80211_bss_get_ie() derefences an RCU to return ssid_ie, both
the call to this function and any operation on this variable need
protection by the RCU read lock.

Fixes: 44905265bc15 ("nl80211: don't expose wdev->ssid for most interfaces")
Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>
---

> but after, perhaps it's easier to just do
>
> if (ssid_ie &&
> nla_put(...)
> goto nla_put_failure_rcu_locked;
>
> and avoid the extra label (but yeah, it's getting late)

OK, done that (and updated the commit message), and testet it.

Thanks,
Dominik

diff --git a/net/wireless/nl80211.c b/net/wireless/nl80211.c
index 2b3dbcd40e46..ed87a97fcb0b 100644
--- a/net/wireless/nl80211.c
+++ b/net/wireless/nl80211.c
@@ -2618,12 +2618,13 @@ static int nl80211_send_iface(struct sk_buff *msg, u32 portid, u32 seq, int flag
const u8 *ssid_ie;
if (!wdev->current_bss)
break;
+ rcu_read_lock();
ssid_ie = ieee80211_bss_get_ie(&wdev->current_bss->pub,
WLAN_EID_SSID);
- if (!ssid_ie)
- break;
- if (nla_put(msg, NL80211_ATTR_SSID, ssid_ie[1], ssid_ie + 2))
- goto nla_put_failure_locked;
+ if (ssid_ie &&
+ nla_put(msg, NL80211_ATTR_SSID, ssid_ie[1], ssid_ie + 2))
+ goto nla_put_failure_rcu_locked;
+ rcu_read_unlock();
break;
}
default:
@@ -2635,6 +2636,8 @@ static int nl80211_send_iface(struct sk_buff *msg, u32 portid, u32 seq, int flag
genlmsg_end(msg, hdr);
return 0;

+ nla_put_failure_rcu_locked:
+ rcu_read_unlock();
nla_put_failure_locked:
wdev_unlock(wdev);
nla_put_failure:
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