netdev - [PATCH net v2] batman-adv: fix OOB read/write in network-coding decode

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Message-Id: <20250831145623.63778-1-disclosure@aisle.com>
Date: Sun, 31 Aug 2025 16:56:23 +0200
From: Stanislav Fort <stanislav.fort@...le.com>
To: netdev@...r.kernel.org
Cc: Marek Lindner <marek.lindner@...lbox.org>,
	Simon Wunderlich <sw@...onwunderlich.de>,
	Antonio Quartulli <antonio@...delbit.com>,
	Sven Eckelmann <sven@...fation.org>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>,
	Simon Horman <horms@...nel.org>,
	b.a.t.m.a.n@...ts.open-mesh.org (moderated list:BATMAN ADVANCED),
	linux-kernel@...r.kernel.org (open list),
	disclosure@...le.com,
	stable@...r.kernel.org
Subject: [PATCH net v2] batman-adv: fix OOB read/write in network-coding decode

batadv_nc_skb_decode_packet() trusts coded_len and checks only against
skb->len. XOR starts at sizeof(struct batadv_unicast_packet), reducing
payload headroom, and the source skb length is not verified, allowing an
out-of-bounds read and a small out-of-bounds write.

Validate that coded_len fits within the payload area of both destination
and source sk_buffs before XORing.

Fixes: 2df5278b0267 ("batman-adv: network coding - receive coded packets and decode them")
Cc: stable@...r.kernel.org
Reported-by: Stanislav Fort <disclosure@...le.com>
Signed-off-by: Stanislav Fort <disclosure@...le.com>
---
 net/batman-adv/network-coding.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/net/batman-adv/network-coding.c b/net/batman-adv/network-coding.c
index 9f56308779cc..af97d077369f 100644
--- a/net/batman-adv/network-coding.c
+++ b/net/batman-adv/network-coding.c
@@ -1687,7 +1687,12 @@ batadv_nc_skb_decode_packet(struct batadv_priv *bat_priv, struct sk_buff *skb,
 
 	coding_len = ntohs(coded_packet_tmp.coded_len);
 
-	if (coding_len > skb->len)
+	/* ensure dst buffer is large enough (payload only) */
+	if (coding_len + h_size > skb->len)
+		return NULL;
+
+	/* ensure src buffer is large enough (payload only) */
+	if (coding_len + h_size > nc_packet->skb->len)
 		return NULL;
 
 	/* Here the magic is reversed:
-- 
2.39.3 (Apple Git-146)