can: j1939: transport: j1939_session_fresh_new(): initialize receive buffer

Zero the allocated buffer in j1939_session_fresh_new() to ensure it
contains no residual data.

While there is a potential performance impact if users allocate maximum
sized ETP buffers, most real-world use cases are not noticeably affected
since the maximum known buffer size is typically around 65K.

Fixes: 9d71dd0c70 ("can: add support of SAE J1939 protocol")
Reported-by: Ji'an Zhou <eilaimemedsnaimel@gmail.com>
Message-ID: <CAPAUci5dykCLjoijqkUtFqJFesgncrD7+S6y_V=gjbFkY2Tifg@mail.gmail.com>
Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Link: https://patch.msgid.link/20260728055835.1151785-3-o.rempel@pengutronix.de
Cc: stable@kernel.org
[mkl: add Message-ID]
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

net/can/j1939/transport.c

@@ -1581,7 +1581,7 @@ j1939_session *j1939_session_fresh_new(struct j1939_priv *priv,
 	}
 
 	/* alloc data area */
-	skb_put(skb, size);
+	skb_put_zero(skb, size);
 	/* skb is recounted in j1939_session_new() */
 	return session;
 }