linux-hardening - [PATCH] e100: replace deprecated strncpy with strscpy

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Message-ID: <20231009-strncpy-drivers-net-ethernet-intel-e100-c-v1-1-ca0ff96868a3@google.com>
Date: Mon, 09 Oct 2023 23:41:01 +0000
From: Justin Stitt <justinstitt@...gle.com>
To: Jesse Brandeburg <jesse.brandeburg@...el.com>, Tony Nguyen <anthony.l.nguyen@...el.com>, 
	"David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, 
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>
Cc: intel-wired-lan@...ts.osuosl.org, netdev@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org, 
	Justin Stitt <justinstitt@...gle.com>
Subject: [PATCH] e100: replace deprecated strncpy with strscpy

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

The "...-1" pattern makes it evident that netdev->name is expected to be
NUL-terminated.

Meanwhile, it seems NUL-padding is not required due to alloc_etherdev
zero-allocating the buffer.

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.

This is in line with other uses of strscpy on netdev->name:
$ rg "strscpy\(netdev\->name.*pci.*"

drivers/net/ethernet/intel/e1000e/netdev.c
7455:   strscpy(netdev->name, pci_name(pdev), sizeof(netdev->name));

drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
10839:  strscpy(netdev->name, pci_name(pdev), sizeof(netdev->name));

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>
---
Note: build-tested only.
---
 drivers/net/ethernet/intel/e100.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/intel/e100.c b/drivers/net/ethernet/intel/e100.c
index d3fdc290937f..01f0f12035ca 100644
--- a/drivers/net/ethernet/intel/e100.c
+++ b/drivers/net/ethernet/intel/e100.c
@@ -2841,7 +2841,7 @@ static int e100_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
 	netdev->netdev_ops = &e100_netdev_ops;
 	netdev->ethtool_ops = &e100_ethtool_ops;
 	netdev->watchdog_timeo = E100_WATCHDOG_PERIOD;
-	strncpy(netdev->name, pci_name(pdev), sizeof(netdev->name) - 1);
+	strscpy(netdev->name, pci_name(pdev), sizeof(netdev->name));
 
 	nic = netdev_priv(netdev);
 	netif_napi_add_weight(netdev, &nic->napi, e100_poll, E100_NAPI_WEIGHT);

---
base-commit: cbf3a2cb156a2c911d8f38d8247814b4c07f49a2
change-id: 20231009-strncpy-drivers-net-ethernet-intel-e100-c-4547179d9f2c

Best regards,
--
Justin Stitt <justinstitt@...gle.com>