Re: [PATCH] net: Fix UAF in ieee80211_scan_rx()

From: Kalle Valo <kvalo@kernel.org>
To: Siddh Raman Pant <code@siddh.me>
Cc: netdev <netdev@vger.kernel.org>,
	linux-wireless <linux-wireless@vger.kernel.org>,
	linux-kernel <linux-kernel@vger.kernel.org>,
	Eric Dumazet <edumazet@google.com>,
	Jakub Kicinski <kuba@kernel.org>,
	Johannes Berg <johannes@sipsolutions.net>,
	Paolo Abeni <pabeni@redhat.com>,
	linux-kernel-mentees
	<linux-kernel-mentees@lists.linuxfoundation.org>,
	"David S . Miller" <davem@davemloft.net>
Subject: Re: [PATCH] net: Fix UAF in ieee80211_scan_rx()
Date: Tue, 26 Jul 2022 12:55:06 +0300	[thread overview]
Message-ID: <8735eomc5h.fsf@kernel.org> (raw)
In-Reply-To: <20220701145423.53208-1-code@siddh.me> (Siddh Raman Pant's message of "Fri, 1 Jul 2022 20:24:23 +0530")

Siddh Raman Pant <code@siddh.me> writes:

> ieee80211_scan_rx() tries to access scan_req->flags after a null check
> (see line 303 of mac80211/scan.c), but ___cfg80211_scan_done() uses
> kfree() on the scan_req (see line 991 of wireless/scan.c).
>
> This results in a UAF.
>
> ieee80211_scan_rx() is called inside a RCU read-critical section
> initiated by ieee80211_rx_napi() (see line 5043 of mac80211/rx.c).
>
> Thus, add an rcu_head to the scan_req struct so as to use kfree_rcu()
> instead of kfree() so that we don't free during the critical section.
>
> Bug report (3): https://syzkaller.appspot.com/bug?extid=f9acff9bf08a845f225d
> Reported-by: syzbot+f9acff9bf08a845f225d@syzkaller.appspotmail.com
> Reported-by: syzbot+6cb476b7c69916a0caca@syzkaller.appspotmail.com
> Reported-by: syzbot+9250865a55539d384347@syzkaller.appspotmail.com
>
> Signed-off-by: Siddh Raman Pant <code@siddh.me>
> ---
>  include/net/cfg80211.h | 2 ++
>  net/wireless/scan.c    | 2 +-
>  2 files changed, 3 insertions(+), 1 deletion(-)

The title should be:

wifi: cfg80211: Fix UAF in ieee80211_scan_rx()

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