[PATCH] nfp: replace deprecated strncpy with strscpy

[PATCH] nfp: replace deprecated strncpy with strscpy

[Justin Stitt]

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@vger.kernel.org
Signed-off-by: Justin Stitt <justinstitt@google.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@google.com>

Re: [PATCH] nfp: replace deprecated strncpy with strscpy

[Kees Cook]

On Wed, Oct 11, 2023 at 09:48:39PM +0000, Justin Stitt wrote:
> 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@vger.kernel.org
> Signed-off-by: Justin Stitt <justinstitt@google.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));

struct nfp_resource {
        char name[NFP_RESOURCE_ENTRY_NAME_SZ + 1];

Yup, this is doing the implicit string size reduction.

Reviewed-by: Kees Cook <keescook@chromium.org>

-- 
Kees Cook

Re: [PATCH] nfp: replace deprecated strncpy with strscpy

[Louis Peens]

On Wed, Oct 11, 2023 at 09:48:39PM +0000, Justin Stitt wrote:
> 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@vger.kernel.org
> Signed-off-by: Justin Stitt <justinstitt@google.com>
> ---
> Note: build-tested only.
> 
> Found with: $ rg "strncpy\("
Thanks Justin, I did also now check it on a nfp.

Acked-by: Louis Peens <louis.peens@corigine.com>
> ---
>  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@google.com>
> 

Re: [PATCH] nfp: replace deprecated strncpy with strscpy

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net-next.git (main)
by Jakub Kicinski <kuba@kernel.org>:

On Wed, 11 Oct 2023 21:48:39 +0000 you wrote:
> 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)) {
> 
> [...]

Here is the summary with links:
  - nfp: replace deprecated strncpy with strscpy
    https://git.kernel.org/netdev/net-next/c/d273e99b5623

You are awesome, thank you!
-- 
Deet-doot-dot, I am a bot.
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