| Message ID | 20231012-strncpy-drivers-net-ethernet-sfc-mcdi-c-v1-1-478c8de1039d@google.com (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | 220dd227ca3aec6ab65fcdfd4549ce12fe326249 |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | sfc: replace deprecated strncpy with strscpy | expand |
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: linux-hardening@vger.kernel.org > Signed-off-by: Justin Stitt <justinstitt@google.com> Acked-by: Edward Cree <ecree.xilinx@gmail.com> 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: linux-hardening@vger.kernel.org > Signed-off-by: Justin Stitt <justinstitt@google.com> Looks correct to me! Reviewed-by: Kees Cook <keescook@chromium.org>
Hello: This patch was applied to netdev/net-next.git (main) by Jakub Kicinski <kuba@kernel.org>: 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!
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'; }
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: linux-hardening@vger.kernel.org Signed-off-by: Justin Stitt <justinstitt@google.com> --- Note: build-tested only. Found with: $ rg "strncpy\(" --- drivers/net/ethernet/sfc/mcdi.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) --- base-commit: cbf3a2cb156a2c911d8f38d8247814b4c07f49a2 change-id: 20231012-strncpy-drivers-net-ethernet-sfc-mcdi-c-cf970a9b7d60 Best regards, -- Justin Stitt <justinstitt@google.com>