linux-kernel - [PATCH 5.10 089/141] sfc: fix null pointer dereference in efx_hard_start

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Message-Id: <20220926100757.660287898@linuxfoundation.org>
Date:   Mon, 26 Sep 2022 12:11:55 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Tianhao Zhao <tizhao@...hat.com>,
        Íñigo Huguet <ihuguet@...hat.com>,
        Edward Cree <ecree.xilinx@...il.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.10 089/141] sfc: fix null pointer dereference in efx_hard_start_xmit

From: Íñigo Huguet <ihuguet@...hat.com>

[ Upstream commit 0a242eb2913a4aa3d6fbdb86559f27628e9466f3 ]

Trying to get the channel from the tx_queue variable here is wrong
because we can only be here if tx_queue is NULL, so we shouldn't
dereference it. As the above comment in the code says, this is very
unlikely to happen, but it's wrong anyway so let's fix it.

I hit this issue because of a different bug that caused tx_queue to be
NULL. If that happens, this is the error message that we get here:
  BUG: unable to handle kernel NULL pointer dereference at 0000000000000020
  [...]
  RIP: 0010:efx_hard_start_xmit+0x153/0x170 [sfc]

Fixes: 12804793b17c ("sfc: decouple TXQ type from label")
Reported-by: Tianhao Zhao <tizhao@...hat.com>
Signed-off-by: Íñigo Huguet <ihuguet@...hat.com>
Acked-by: Edward Cree <ecree.xilinx@...il.com>
Link: https://lore.kernel.org/r/20220914111135.21038-1-ihuguet@redhat.com
Signed-off-by: Jakub Kicinski <kuba@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/net/ethernet/sfc/tx.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/sfc/tx.c b/drivers/net/ethernet/sfc/tx.c
index 1665529a7271..fcc7de8ae2bf 100644
--- a/drivers/net/ethernet/sfc/tx.c
+++ b/drivers/net/ethernet/sfc/tx.c
@@ -545,7 +545,7 @@ netdev_tx_t efx_hard_start_xmit(struct sk_buff *skb,
 		 * previous packets out.
 		 */
 		if (!netdev_xmit_more())
-			efx_tx_send_pending(tx_queue->channel);
+			efx_tx_send_pending(efx_get_tx_channel(efx, index));
 		return NETDEV_TX_OK;
 	}
 
-- 
2.35.1