linux-kernel - [PATCH] nfp: replace deprecated strncpy with strscpy

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Message-ID: <20231011-strncpy-drivers-net-ethernet-netronome-nfp-nfpcore-nfp_resource-c-v1-1-7d1c984f0eba@google.com>
Date:   Wed, 11 Oct 2023 21:48:39 +0000
From:   Justin Stitt <justinstitt@...gle.com>
To:     Louis Peens <louis.peens@...igine.com>,
        Jakub Kicinski <kuba@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Paolo Abeni <pabeni@...hat.com>
Cc:     oss-drivers@...igine.com, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org,
        Justin Stitt <justinstitt@...gle.com>
Subject: [PATCH] nfp: 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.

We expect res->name to be NUL-terminated based on its usage with format
strings:
|       dev_err(cpp->dev.parent, "Dangling area: %d:%d:%d:0x%0llx-0x%0llx%s%s\n",
|               NFP_CPP_ID_TARGET_of(res->cpp_id),
|               NFP_CPP_ID_ACTION_of(res->cpp_id),
|               NFP_CPP_ID_TOKEN_of(res->cpp_id),
|               res->start, res->end,
|               res->name ? " " : "",
|               res->name ? res->name : "");
... and with strcmp()
|       if (!strcmp(res->name, NFP_RESOURCE_TBL_NAME)) {

Moreover, NUL-padding is not required as `res` is already
zero-allocated:
|       res = kzalloc(sizeof(*res), GFP_KERNEL);

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.

Let's also opt to use the more idiomatic strscpy() usage of (dest, src,
sizeof(dest)) rather than (dest, src, SOME_LEN).

Typically the pattern of 1) allocate memory for string, 2) copy string
into freshly-allocated memory is a candidate for kmemdup_nul() but in
this case we are allocating the entirety of the `res` struct and that
should stay as is. As mentioned above, simple 1:1 replacement of strncpy
-> strscpy :)

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.

Found with: $ rg "strncpy\("
---
 drivers/net/ethernet/netronome/nfp/nfpcore/nfp_resource.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/netronome/nfp/nfpcore/nfp_resource.c b/drivers/net/ethernet/netronome/nfp/nfpcore/nfp_resource.c
index ce7492a6a98f..279ea0b56955 100644
--- a/drivers/net/ethernet/netronome/nfp/nfpcore/nfp_resource.c
+++ b/drivers/net/ethernet/netronome/nfp/nfpcore/nfp_resource.c
@@ -159,7 +159,7 @@ nfp_resource_acquire(struct nfp_cpp *cpp, const char *name)
 	if (!res)
 		return ERR_PTR(-ENOMEM);
 
-	strncpy(res->name, name, NFP_RESOURCE_ENTRY_NAME_SZ);
+	strscpy(res->name, name, sizeof(res->name));
 
 	dev_mutex = nfp_cpp_mutex_alloc(cpp, NFP_RESOURCE_TBL_TARGET,
 					NFP_RESOURCE_TBL_BASE,

---
base-commit: cbf3a2cb156a2c911d8f38d8247814b4c07f49a2
change-id: 20231011-strncpy-drivers-net-ethernet-netronome-nfp-nfpcore-nfp_resource-c-1812b8357fcd

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