linux-hardening - [PATCH v2] net: ena: replace deprecated strncpy with strscpy

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Message-ID: <20231207-strncpy-drivers-net-ethernet-amazon-ena-ena_netdev-c-v2-1-a1f2893d1b70@google.com>
Date: Thu, 07 Dec 2023 21:34:42 +0000
From: justinstitt@...gle.com
To: Shay Agroskin <shayagr@...zon.com>, Arthur Kiyanovski <akiyano@...zon.com>, 
	David Arinzon <darinzon@...zon.com>, Noam Dagan <ndagan@...zon.com>, 
	Saeed Bishara <saeedb@...zon.com>, "David S. Miller" <davem@...emloft.net>, 
	Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>
Cc: netdev@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-hardening@...r.kernel.org, Justin Stitt <justinstitt@...gle.com>
Subject: [PATCH v2] net: ena: 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.

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

host_info allocation is done in ena_com_allocate_host_info() via
dma_alloc_coherent() and is not zero initialized by alloc_etherdev_mq().

However zero initialization of the destination doesn't matter in this case,
because strscpy() guarantees a NULL termination.

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>
---
Changes in v2:
- update commit message, dropping inaccurate statement about allocation
  (thanks Arthur)
- copy/paste Arthur's explanation regarding host_info allocation into
- rebased onto mainline
- Link to v1: https://lore.kernel.org/r/20231005-strncpy-drivers-net-ethernet-amazon-ena-ena_netdev-c-v1-1-ba4879974160@google.com
---
Note: build-tested only.
---
 drivers/net/ethernet/amazon/ena/ena_netdev.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/amazon/ena/ena_netdev.c b/drivers/net/ethernet/amazon/ena/ena_netdev.c
index b5bca4814830..4a41efcc996b 100644
--- a/drivers/net/ethernet/amazon/ena/ena_netdev.c
+++ b/drivers/net/ethernet/amazon/ena/ena_netdev.c
@@ -3276,8 +3276,8 @@ static void ena_config_host_info(struct ena_com_dev *ena_dev, struct pci_dev *pd
 	strscpy(host_info->kernel_ver_str, utsname()->version,
 		sizeof(host_info->kernel_ver_str) - 1);
 	host_info->os_dist = 0;
-	strncpy(host_info->os_dist_str, utsname()->release,
-		sizeof(host_info->os_dist_str) - 1);
+	strscpy(host_info->os_dist_str, utsname()->release,
+		sizeof(host_info->os_dist_str));
 	host_info->driver_version =
 		(DRV_MODULE_GEN_MAJOR) |
 		(DRV_MODULE_GEN_MINOR << ENA_ADMIN_HOST_INFO_MINOR_SHIFT) |

---
base-commit: bee0e7762ad2c6025b9f5245c040fcc36ef2bde8
change-id: 20231005-strncpy-drivers-net-ethernet-amazon-ena-ena_netdev-c-6c4804466aa7

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