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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Marc Kleine-Budde <mkl@pengutronix.de>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 4.19 029/321] can: rx-offload: can_rx_offload_offload_one(): do not increase the skb_queue beyond skb_queue_len_max
Date:   Tue,  3 Dec 2019 23:31:35 +0100
Message-Id: <20191203223428.633153096@linuxfoundation.org>
In-Reply-To: <20191203223427.103571230@linuxfoundation.org>
References: <20191203223427.103571230@linuxfoundation.org>
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From: Marc Kleine-Budde <mkl@pengutronix.de>

[ Upstream commit a2dc3f5e1022a5ede8af9ab89a144f1e69db8636 ]

The skb_queue is a linked list, holding the skb to be processed in the
next NAPI call.

Without this patch, the queue length in can_rx_offload_offload_one() is
limited to skb_queue_len_max + 1. As the skb_queue is a linked list, no
array or other resources are accessed out-of-bound, however this
behaviour is counterintuitive.

This patch limits the rx-offload skb_queue length to skb_queue_len_max.

Fixes: d254586c3453 ("can: rx-offload: Add support for HW fifo based irq offloading")
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/net/can/rx-offload.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/can/rx-offload.c b/drivers/net/can/rx-offload.c
index a90005eac8b17..e32b65599a5f2 100644
--- a/drivers/net/can/rx-offload.c
+++ b/drivers/net/can/rx-offload.c
@@ -124,7 +124,7 @@ static struct sk_buff *can_rx_offload_offload_one(struct can_rx_offload *offload
 	int ret;
 
 	/* If queue is full or skb not available, read to discard mailbox */
-	if (likely(skb_queue_len(&offload->skb_queue) <=
+	if (likely(skb_queue_len(&offload->skb_queue) <
 		   offload->skb_queue_len_max))
 		skb = alloc_can_skb(offload->dev, &cf);
 
-- 
2.20.1