[PATCH 5.15 100/177] net/packet: rx_owner_map depends on pg_vec

[Greg Kroah-Hartman]

From: Willem de Bruijn <willemb@xxxxxxxxxx>

[ Upstream commit ec6af094ea28f0f2dda1a6a33b14cd57e36a9755 ]

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@xxxxxxxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Willem de Bruijn <willemb@xxxxxxxxxx>
Reviewed-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20211215143937.106178-1-willemdebruijn.kernel@xxxxxxxxx
Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 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 2a2bc64f75cfd..1bc7ef49e1487 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -4457,9 +4457,10 @@ 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;
 }
-- 
2.33.0