[PATCH] octeontx2-af: replace deprecated strncpy with strscpy

[PATCH] octeontx2-af: 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 can see that linfo->lmac_type is expected to be NUL-terminated based
on the `... - 1`'s present in the current code. Presumably making room
for a NUL-byte at the end of 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.

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

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.
---
 drivers/net/ethernet/marvell/octeontx2/af/cgx.c | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/drivers/net/ethernet/marvell/octeontx2/af/cgx.c b/drivers/net/ethernet/marvell/octeontx2/af/cgx.c
index e06f77ad6106..6c70c8498690 100644
--- a/drivers/net/ethernet/marvell/octeontx2/af/cgx.c
+++ b/drivers/net/ethernet/marvell/octeontx2/af/cgx.c
@@ -1218,8 +1218,6 @@ static inline void link_status_user_format(u64 lstat,
 					   struct cgx_link_user_info *linfo,
 					   struct cgx *cgx, u8 lmac_id)
 {
-	const char *lmac_string;
-
 	linfo->link_up = FIELD_GET(RESP_LINKSTAT_UP, lstat);
 	linfo->full_duplex = FIELD_GET(RESP_LINKSTAT_FDUPLEX, lstat);
 	linfo->speed = cgx_speed_mbps[FIELD_GET(RESP_LINKSTAT_SPEED, lstat)];
@@ -1230,12 +1228,12 @@ static inline void link_status_user_format(u64 lstat,
 	if (linfo->lmac_type_id >= LMAC_MODE_MAX) {
 		dev_err(&cgx->pdev->dev, "Unknown lmac_type_id %d reported by firmware on cgx port%d:%d",
 			linfo->lmac_type_id, cgx->cgx_id, lmac_id);
-		strncpy(linfo->lmac_type, "Unknown", LMACTYPE_STR_LEN - 1);
+		strscpy(linfo->lmac_type, "Unknown", sizeof(linfo->lmac_type));
 		return;
 	}
 
-	lmac_string = cgx_lmactype_string[linfo->lmac_type_id];
-	strncpy(linfo->lmac_type, lmac_string, LMACTYPE_STR_LEN - 1);
+	strscpy(linfo->lmac_type, cgx_lmactype_string[linfo->lmac_type_id],
+		sizeof(linfo->lmac_type));
 }
 
 /* Hardware event handlers */

---
base-commit: cbf3a2cb156a2c911d8f38d8247814b4c07f49a2
change-id: 20231010-strncpy-drivers-net-ethernet-marvell-octeontx2-af-cgx-c-529077646c6a

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

Re: [PATCH] octeontx2-af: replace deprecated strncpy with strscpy

[Kees Cook]

On Tue, Oct 10, 2023 at 09:38:11PM +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 can see that linfo->lmac_type is expected to be NUL-terminated based
> on the `... - 1`'s present in the current code. Presumably making room
> for a NUL-byte at the end of 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.
> 
> Let's also prefer the more idiomatic strscpy usage of (dest, src,
> sizeof(dest)) rather than (dest, src, SOME_LEN).
> 
> 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.
> ---
>  drivers/net/ethernet/marvell/octeontx2/af/cgx.c | 8 +++-----
>  1 file changed, 3 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/net/ethernet/marvell/octeontx2/af/cgx.c b/drivers/net/ethernet/marvell/octeontx2/af/cgx.c
> index e06f77ad6106..6c70c8498690 100644
> --- a/drivers/net/ethernet/marvell/octeontx2/af/cgx.c
> +++ b/drivers/net/ethernet/marvell/octeontx2/af/cgx.c
> @@ -1218,8 +1218,6 @@ static inline void link_status_user_format(u64 lstat,
>  					   struct cgx_link_user_info *linfo,
>  					   struct cgx *cgx, u8 lmac_id)
>  {
> -	const char *lmac_string;
> -
>  	linfo->link_up = FIELD_GET(RESP_LINKSTAT_UP, lstat);
>  	linfo->full_duplex = FIELD_GET(RESP_LINKSTAT_FDUPLEX, lstat);
>  	linfo->speed = cgx_speed_mbps[FIELD_GET(RESP_LINKSTAT_SPEED, lstat)];
> @@ -1230,12 +1228,12 @@ static inline void link_status_user_format(u64 lstat,
>  	if (linfo->lmac_type_id >= LMAC_MODE_MAX) {
>  		dev_err(&cgx->pdev->dev, "Unknown lmac_type_id %d reported by firmware on cgx port%d:%d",
>  			linfo->lmac_type_id, cgx->cgx_id, lmac_id);
> -		strncpy(linfo->lmac_type, "Unknown", LMACTYPE_STR_LEN - 1);
> +		strscpy(linfo->lmac_type, "Unknown", sizeof(linfo->lmac_type));
>  		return;
>  	}
>  
> -	lmac_string = cgx_lmactype_string[linfo->lmac_type_id];
> -	strncpy(linfo->lmac_type, lmac_string, LMACTYPE_STR_LEN - 1);
> +	strscpy(linfo->lmac_type, cgx_lmactype_string[linfo->lmac_type_id],
> +		sizeof(linfo->lmac_type));

Yup, sizes match. Good replacement and simplification.

drivers/net/ethernet/marvell/octeontx2/af/mbox.h:565:#define LMACTYPE_STR_LEN 16
drivers/net/ethernet/marvell/octeontx2/af/mbox.h:566:   char lmac_type[LMACTYPE_STR_LEN];

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

-- 
Kees Cook

Re: [PATCH] octeontx2-af: 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 Tue, 10 Oct 2023 21:38:11 +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 can see that linfo->lmac_type is expected to be NUL-terminated based
> on the `... - 1`'s present in the current code. Presumably making room
> for a NUL-byte at the end of the buffer.
> 
> [...]

Here is the summary with links:
  - octeontx2-af: replace deprecated strncpy with strscpy
    https://git.kernel.org/netdev/net-next/c/473f8f2d1bfe

You are awesome, thank you!
-- 
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