netdev - [PATCH net] net/packet: rx_owner_map depends on pg

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Message-Id: <20211215143937.106178-1-willemdebruijn.kernel@gmail.com>
Date:   Wed, 15 Dec 2021 09:39:37 -0500
From:   Willem de Bruijn <willemdebruijn.kernel@...il.com>
To:     netdev@...r.kernel.org
Cc:     davem@...emloft.net, kuba@...nel.org, theflow@...gle.com,
        Willem de Bruijn <willemb@...gle.com>,
        Syzbot <syzbot+1ac0994a0a0c55151121@...kaller.appspotmail.com>,
        Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH net] net/packet: rx_owner_map depends on pg_vec

From: Willem de Bruijn <willemb@...gle.com>

Packet sockets may switch ring versions. Avoid misinterpreting state
between versions, whose fields share a union. rx_owner_map is only
allocated with a packet ring (pg_vec) and both are swapped together.
If pg_vec is NULL, meaning no packet ring was allocated, then neither
was rx_owner_map. And the field may be old state from a tpacket_v3.

Fixes: 61fad6816fc1 ("net/packet: tpacket_rcv: avoid a producer race condition")
Reported-by: Syzbot <syzbot+1ac0994a0a0c55151121@...kaller.appspotmail.com>
Signed-off-by: Willem de Bruijn <willemb@...gle.com>
Reviewed-by: Eric Dumazet <edumazet@...gle.com>
---
 net/packet/af_packet.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index 46943a18a10d..76c2dca7f0a5 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -4492,9 +4492,10 @@ static int packet_set_ring(struct sock *sk, union tpacket_req_u *req_u,
 	}
 
 out_free_pg_vec:
-	bitmap_free(rx_owner_map);
-	if (pg_vec)
+	if (pg_vec) {
+		bitmap_free(rx_owner_map);
 		free_pg_vec(pg_vec, order, req->tp_block_nr);
+	}
 out:
 	return err;
 }
-- 
2.34.1.173.g76aa8bc2d0-goog