strncpy() is deprecated for use on NUL-terminated destination strings
[1] and as such we should prefer more robust and less ambiguous string
interfaces.
`desc` is expected to be NUL-terminated as evident by the manual
NUL-byte assignment. Moreover, NUL-padding does not seem to be
necessary.
The only caller of efx_mcdi_nvram_metadata() is
efx_devlink_info_nvram_partition() which provides a NULL for `desc`:
| rc = efx_mcdi_nvram_metadata(efx, partition_type, NULL, version, NULL, 0);
Due to this, I am not sure this code is even reached but we should still
favor something other than strncpy.
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.
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: [email protected]
Signed-off-by: Justin Stitt <[email protected]>
---
Note: build-tested only.
Found with: $ rg "strncpy\("
---
drivers/net/ethernet/sfc/mcdi.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/drivers/net/ethernet/sfc/mcdi.c b/drivers/net/ethernet/sfc/mcdi.c
index d23da9627338..76578502226e 100644
--- a/drivers/net/ethernet/sfc/mcdi.c
+++ b/drivers/net/ethernet/sfc/mcdi.c
@@ -2205,10 +2205,9 @@ int efx_mcdi_nvram_metadata(struct efx_nic *efx, unsigned int type,
goto out_free;
}
- strncpy(desc,
+ strscpy(desc,
MCDI_PTR(outbuf, NVRAM_METADATA_OUT_DESCRIPTION),
MC_CMD_NVRAM_METADATA_OUT_DESCRIPTION_NUM(outlen));
- desc[MC_CMD_NVRAM_METADATA_OUT_DESCRIPTION_NUM(outlen)] = '\0';
} else {
desc[0] = '\0';
}
---
base-commit: cbf3a2cb156a2c911d8f38d8247814b4c07f49a2
change-id: 20231012-strncpy-drivers-net-ethernet-sfc-mcdi-c-cf970a9b7d60
Best regards,
--
Justin Stitt <[email protected]>
On 12/10/2023 21:38, 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.
>
> `desc` is expected to be NUL-terminated as evident by the manual
> NUL-byte assignment. Moreover, NUL-padding does not seem to be
> necessary.
>
> The only caller of efx_mcdi_nvram_metadata() is
> efx_devlink_info_nvram_partition() which provides a NULL for `desc`:
> | rc = efx_mcdi_nvram_metadata(efx, partition_type, NULL, version, NULL, 0);
>
> Due to this, I am not sure this code is even reached but we should still
> favor something other than strncpy.
>
> 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.
>
> 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: [email protected]
> Signed-off-by: Justin Stitt <[email protected]>
Acked-by: Edward Cree <[email protected]>
but ideally we should just rip out the dead code instead. If this
patch gets taken as-is into net-next then I can probably do that
in a follow-up.
-ed
On Thu, Oct 12, 2023 at 08:38:19PM +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.
>
> `desc` is expected to be NUL-terminated as evident by the manual
> NUL-byte assignment. Moreover, NUL-padding does not seem to be
> necessary.
>
> The only caller of efx_mcdi_nvram_metadata() is
> efx_devlink_info_nvram_partition() which provides a NULL for `desc`:
> | rc = efx_mcdi_nvram_metadata(efx, partition_type, NULL, version, NULL, 0);
>
> Due to this, I am not sure this code is even reached but we should still
> favor something other than strncpy.
>
> 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.
>
> 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: [email protected]
> Signed-off-by: Justin Stitt <[email protected]>
Looks correct to me!
Reviewed-by: Kees Cook <[email protected]>
--
Kees Cook
Hello:
This patch was applied to netdev/net-next.git (main)
by Jakub Kicinski <[email protected]>:
On Thu, 12 Oct 2023 20:38:19 +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.
>
> `desc` is expected to be NUL-terminated as evident by the manual
> NUL-byte assignment. Moreover, NUL-padding does not seem to be
> necessary.
>
> [...]
Here is the summary with links:
- sfc: replace deprecated strncpy with strscpy
https://git.kernel.org/netdev/net-next/c/220dd227ca3a
You are awesome, thank you!
--
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