netdev - [PATCH net-next] tsnep: Fix tsnep_request

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Message-Id: <20231023183856.58373-1-gerhard@engleder-embedded.com>
Date: Mon, 23 Oct 2023 20:38:56 +0200
From: Gerhard Engleder <gerhard@...leder-embedded.com>
To: netdev@...r.kernel.org
Cc: davem@...emloft.net,
	kuba@...nel.org,
	edumazet@...gle.com,
	pabeni@...hat.com,
	Gerhard Engleder <gerhard@...leder-embedded.com>,
	kernel test robot <lkp@...el.com>
Subject: [PATCH net-next] tsnep: Fix tsnep_request_irq() format-overflow warning

Compiler warns about a possible format-overflow in tsnep_request_irq():
drivers/net/ethernet/engleder/tsnep_main.c:884:55: warning: 'sprintf' may write a terminating nul past the end of the destination [-Wformat-overflow=]
                         sprintf(queue->name, "%s-rx-%d", name,
                                                       ^
drivers/net/ethernet/engleder/tsnep_main.c:881:55: warning: 'sprintf' may write a terminating nul past the end of the destination [-Wformat-overflow=]
                         sprintf(queue->name, "%s-tx-%d", name,
                                                       ^
drivers/net/ethernet/engleder/tsnep_main.c:878:49: warning: '-txrx-' directive writing 6 bytes into a region of size between 5 and 25 [-Wformat-overflow=]
                         sprintf(queue->name, "%s-txrx-%d", name,
                                                 ^~~~~~

Actually overflow cannot happen. Name is limited to IFNAMSIZ, because
netdev_name() is called during ndo_open(). queue_index is single char,
because less than 10 queues are supported.

Fix warning with snprintf(). Additionally increase buffer to 32 bytes,
because those 7 additional bytes were unused anyway.

Reported-by: kernel test robot <lkp@...el.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202310182028.vmDthIUa-lkp@intel.com/
Signed-off-by: Gerhard Engleder <gerhard@...leder-embedded.com>
---
 drivers/net/ethernet/engleder/tsnep.h      |  2 +-
 drivers/net/ethernet/engleder/tsnep_main.c | 12 ++++++------
 2 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/drivers/net/ethernet/engleder/tsnep.h b/drivers/net/ethernet/engleder/tsnep.h
index 6e14c918e3fb..f188fba021a6 100644
--- a/drivers/net/ethernet/engleder/tsnep.h
+++ b/drivers/net/ethernet/engleder/tsnep.h
@@ -143,7 +143,7 @@ struct tsnep_rx {
 
 struct tsnep_queue {
 	struct tsnep_adapter *adapter;
-	char name[IFNAMSIZ + 9];
+	char name[IFNAMSIZ + 16];
 
 	struct tsnep_tx *tx;
 	struct tsnep_rx *rx;
diff --git a/drivers/net/ethernet/engleder/tsnep_main.c b/drivers/net/ethernet/engleder/tsnep_main.c
index f16b6b3e21a6..df40c720e7b2 100644
--- a/drivers/net/ethernet/engleder/tsnep_main.c
+++ b/drivers/net/ethernet/engleder/tsnep_main.c
@@ -1830,14 +1830,14 @@ static int tsnep_request_irq(struct tsnep_queue *queue, bool first)
 		dev = queue->adapter;
 	} else {
 		if (queue->tx && queue->rx)
-			sprintf(queue->name, "%s-txrx-%d", name,
-				queue->rx->queue_index);
+			snprintf(queue->name, sizeof(queue->name), "%s-txrx-%d",
+				 name, queue->rx->queue_index);
 		else if (queue->tx)
-			sprintf(queue->name, "%s-tx-%d", name,
-				queue->tx->queue_index);
+			snprintf(queue->name, sizeof(queue->name), "%s-tx-%d",
+				 name, queue->tx->queue_index);
 		else
-			sprintf(queue->name, "%s-rx-%d", name,
-				queue->rx->queue_index);
+			snprintf(queue->name, sizeof(queue->name), "%s-rx-%d",
+				 name, queue->rx->queue_index);
 		handler = tsnep_irq_txrx;
 		dev = queue;
 	}
-- 
2.39.2