linux-hardening - [PATCH net-next 7/9] igb: replace deprecated strncpy with strscpy

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Date: Tue, 17 Oct 2023 12:04:09 -0700
From: Jacob Keller <jacob.e.keller@...el.com>
To: netdev@...r.kernel.org,
	David Miller <davem@...emloft.net>,
	Jakub Kicinski <kuba@...nel.org>
Cc: Justin Stitt <justinstitt@...gle.com>,
	linux-hardening@...r.kernel.org,
	Pucha Himasekhar Reddy <himasekharx.reddy.pucha@...el.com>,
	Jacob Keller <jacob.e.keller@...el.com>
Subject: [PATCH net-next 7/9] igb: replace deprecated strncpy with strscpy

From: Justin Stitt <justinstitt@...gle.com>

`strncpy` is deprecated for use on NUL-terminated destination strings
[1] and as such we should prefer more robust and less ambiguous string
interfaces.

We see that netdev->name is expected to be NUL-terminated based on its
usage with format strings:
|       sprintf(q_vector->name, "%s-TxRx-%u", netdev->name,
|               q_vector->rx.ring->queue_index);

Furthermore, NUL-padding is not required as netdev is already
zero-allocated:
|       netdev = alloc_etherdev_mq(sizeof(struct igb_adapter),
|                                  IGB_MAX_TX_QUEUES);
...
alloc_etherdev_mq() -> alloc_etherdev_mqs() -> alloc_netdev_mqs() ...
|       p = kvzalloc(alloc_size, GFP_KERNEL_ACCOUNT | __GFP_RETRY_MAYFAIL);

Considering the above, a suitable replacement is `strscpy` [2] due to
the fact that it guarantees NUL-termination on the destination buffer
without unnecessarily NUL-padding.

Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [1]
Link: https://manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html [2]
Link: https://github.com/KSPP/linux/issues/90
Cc: linux-hardening@...r.kernel.org
Signed-off-by: Justin Stitt <justinstitt@...gle.com>
Tested-by: Pucha Himasekhar Reddy <himasekharx.reddy.pucha@...el.com> (A Contingent worker at Intel)
Signed-off-by: Jacob Keller <jacob.e.keller@...el.com>
---
 drivers/net/ethernet/intel/igb/igb_main.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/intel/igb/igb_main.c b/drivers/net/ethernet/intel/igb/igb_main.c
index fdadf3e84f59..db54453e1946 100644
--- a/drivers/net/ethernet/intel/igb/igb_main.c
+++ b/drivers/net/ethernet/intel/igb/igb_main.c
@@ -3263,7 +3263,7 @@ static int igb_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
 	igb_set_ethtool_ops(netdev);
 	netdev->watchdog_timeo = 5 * HZ;
 
-	strncpy(netdev->name, pci_name(pdev), sizeof(netdev->name) - 1);
+	strscpy(netdev->name, pci_name(pdev), sizeof(netdev->name));
 
 	netdev->mem_start = pci_resource_start(pdev, 0);
 	netdev->mem_end = pci_resource_end(pdev, 0);
-- 
2.41.0