strncpy() is deprecated for use on NUL-terminated destination strings
[1] and as such we should prefer more robust and less ambiguous string
interfaces.

Based on usage part_str usage within txgbe_read_pba_string(), we expect
part_str to be NUL-terminated but not necessarily NUL-padded:
|       /* put a null character on the end of our string */
|       pba_num[10] = '\0';

Interestingly, part_str is not used after txgbe_read_pba_string():
| ...
|	err = txgbe_read_pba_string(wx, part_str, TXGBE_PBANUM_LENGTH);
|	if (err)
|		strscpy(part_str, "Unknown", sizeof(part_str));
|
|	netif_info(wx, probe, netdev, "%pM\n", netdev->dev_addr);
|
|	return 0;
|
|err_remove_phy:
|	txgbe_remove_phy(txgbe);
|err_release_hw:
|	wx_clear_interrupt_scheme(wx);
|	wx_control_hw(wx, false);
|err_free_mac_table:
|	kfree(wx->mac_table);
|err_pci_release_regions:
|	pci_release_selected_regions(pdev,
|				     pci_select_bars(pdev, IORESOURCE_MEM));
|err_pci_disable_dev:
|	pci_disable_device(pdev);
|	return err;
|}
... this means this strncpy (or now strscpy) is probably useless. For
now, let's make the swap to strscpy() as I am not sure if this is truly
dead code or not.

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/wangxun/txgbe/txgbe_main.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/wangxun/txgbe/txgbe_main.c b/drivers/net/ethernet/wangxun/txgbe/txgbe_main.c
index 5c3aed516ac2..c795fbab37be 100644
--- a/drivers/net/ethernet/wangxun/txgbe/txgbe_main.c
+++ b/drivers/net/ethernet/wangxun/txgbe/txgbe_main.c
@@ -739,7 +739,7 @@ static int txgbe_probe(struct pci_dev *pdev,
 	/* First try to read PBA as a string */
 	err = txgbe_read_pba_string(wx, part_str, TXGBE_PBANUM_LENGTH);
 	if (err)
-		strncpy(part_str, "Unknown", TXGBE_PBANUM_LENGTH);
+		strscpy(part_str, "Unknown", sizeof(part_str));
 
 	netif_info(wx, probe, netdev, "%pM\n", netdev->dev_addr);
 

---
base-commit: cbf3a2cb156a2c911d8f38d8247814b4c07f49a2
change-id: 20231012-strncpy-drivers-net-ethernet-wangxun-txgbe-txgbe_main-c-05152bafac20

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

On Thu, Oct 12, 2023 at 09:20:04PM +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.
> 
> Based on usage part_str usage within txgbe_read_pba_string(), we expect
> part_str to be NUL-terminated but not necessarily NUL-padded:
> |       /* put a null character on the end of our string */
> |       pba_num[10] = '\0';
> 
> Interestingly, part_str is not used after txgbe_read_pba_string():
> | ...
> |	err = txgbe_read_pba_string(wx, part_str, TXGBE_PBANUM_LENGTH);
> |	if (err)
> |		strscpy(part_str, "Unknown", sizeof(part_str));
> |
> |	netif_info(wx, probe, netdev, "%pM\n", netdev->dev_addr);
> |
> |	return 0;
> |
> |err_remove_phy:
> |	txgbe_remove_phy(txgbe);
> |err_release_hw:
> |	wx_clear_interrupt_scheme(wx);
> |	wx_control_hw(wx, false);
> |err_free_mac_table:
> |	kfree(wx->mac_table);
> |err_pci_release_regions:
> |	pci_release_selected_regions(pdev,
> |				     pci_select_bars(pdev, IORESOURCE_MEM));
> |err_pci_disable_dev:
> |	pci_disable_device(pdev);
> |	return err;
> |}
> ... this means this strncpy (or now strscpy) is probably useless. For
> now, let's make the swap to strscpy() as I am not sure if this is truly
> dead code or not.

Hi Julian

I agree, this looks like dead code.

Jiawen, please could you submit a patch cleaning this up. Either swap
to strscpy() and make use of the string, or delete it all.


    Andrew

---
pw-bot: cr

On Sunday, October 15, 2023 12:31 AM, Andrew Lunn wrote:
> On Thu, Oct 12, 2023 at 09:20:04PM +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.
> >
> > Based on usage part_str usage within txgbe_read_pba_string(), we expect
> > part_str to be NUL-terminated but not necessarily NUL-padded:
> > |       /* put a null character on the end of our string */
> > |       pba_num[10] = '\0';
> >
> > Interestingly, part_str is not used after txgbe_read_pba_string():
> > | ...
> > |	err = txgbe_read_pba_string(wx, part_str, TXGBE_PBANUM_LENGTH);
> > |	if (err)
> > |		strscpy(part_str, "Unknown", sizeof(part_str));
> > |
> > |	netif_info(wx, probe, netdev, "%pM\n", netdev->dev_addr);
> > |
> > |	return 0;
> > |
> > |err_remove_phy:
> > |	txgbe_remove_phy(txgbe);
> > |err_release_hw:
> > |	wx_clear_interrupt_scheme(wx);
> > |	wx_control_hw(wx, false);
> > |err_free_mac_table:
> > |	kfree(wx->mac_table);
> > |err_pci_release_regions:
> > |	pci_release_selected_regions(pdev,
> > |				     pci_select_bars(pdev, IORESOURCE_MEM));
> > |err_pci_disable_dev:
> > |	pci_disable_device(pdev);
> > |	return err;
> > |}
> > ... this means this strncpy (or now strscpy) is probably useless. For
> > now, let's make the swap to strscpy() as I am not sure if this is truly
> > dead code or not.
> 
> Hi Julian
> 
> I agree, this looks like dead code.
> 
> Jiawen, please could you submit a patch cleaning this up. Either swap
> to strscpy() and make use of the string, or delete it all.

Ah, I think I missed a line to print this string. I'm going to add it.