[PATCH] net: dsa: vsc73xx: replace deprecated strncpy with ethtool_sprintf

[PATCH] net: dsa: vsc73xx: replace deprecated strncpy with ethtool_sprintf

[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.

ethtool_sprintf() is designed specifically for get_strings() usage.
Let's replace strncpy in favor of this more robust and easier to
understand interface.

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/dsa/vitesse-vsc73xx-core.c | 20 ++++++--------------
 1 file changed, 6 insertions(+), 14 deletions(-)

diff --git a/drivers/net/dsa/vitesse-vsc73xx-core.c b/drivers/net/dsa/vitesse-vsc73xx-core.c
index 4f09e7438f3b..09955fdea2ff 100644
--- a/drivers/net/dsa/vitesse-vsc73xx-core.c
+++ b/drivers/net/dsa/vitesse-vsc73xx-core.c
@@ -928,7 +928,8 @@ static void vsc73xx_get_strings(struct dsa_switch *ds, int port, u32 stringset,
 	const struct vsc73xx_counter *cnt;
 	struct vsc73xx *vsc = ds->priv;
 	u8 indices[6];
-	int i, j;
+	u8 *buf = data;
+	int i;
 	u32 val;
 	int ret;
 
@@ -948,10 +949,7 @@ static void vsc73xx_get_strings(struct dsa_switch *ds, int port, u32 stringset,
 	indices[5] = ((val >> 26) & 0x1f); /* TX counter 2 */
 
 	/* The first counters is the RX octets */
-	j = 0;
-	strncpy(data + j * ETH_GSTRING_LEN,
-		"RxEtherStatsOctets", ETH_GSTRING_LEN);
-	j++;
+	ethtool_sprintf(&buf, "RxEtherStatsOctets");
 
 	/* Each port supports recording 3 RX counters and 3 TX counters,
 	 * figure out what counters we use in this set-up and return the
@@ -962,22 +960,16 @@ static void vsc73xx_get_strings(struct dsa_switch *ds, int port, u32 stringset,
 	for (i = 0; i < 3; i++) {
 		cnt = vsc73xx_find_counter(vsc, indices[i], false);
 		if (cnt)
-			strncpy(data + j * ETH_GSTRING_LEN,
-				cnt->name, ETH_GSTRING_LEN);
-		j++;
+			ethtool_sprintf(&buf, "%s", cnt->name);
 	}
 
 	/* TX stats begins with the number of TX octets */
-	strncpy(data + j * ETH_GSTRING_LEN,
-		"TxEtherStatsOctets", ETH_GSTRING_LEN);
-	j++;
+	ethtool_sprintf(&buf, "TxEtherStatsOctets");
 
 	for (i = 3; i < 6; i++) {
 		cnt = vsc73xx_find_counter(vsc, indices[i], true);
 		if (cnt)
-			strncpy(data + j * ETH_GSTRING_LEN,
-				cnt->name, ETH_GSTRING_LEN);
-		j++;
+			ethtool_sprintf(&buf, "%s", cnt->name);
 	}
 }
 

---
base-commit: cbf3a2cb156a2c911d8f38d8247814b4c07f49a2
change-id: 20231009-strncpy-drivers-net-dsa-vitesse-vsc73xx-core-c-1cfd0ac2d81b

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

Re: [PATCH] net: dsa: vsc73xx: replace deprecated strncpy with ethtool_sprintf

[Florian Fainelli]

On 10/9/23 15:54, 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.
> 
> ethtool_sprintf() is designed specifically for get_strings() usage.
> Let's replace strncpy in favor of this more robust and easier to
> understand interface.
> 
> 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>

Reviewed-by: Florian Fainelli <florian.fainelli@broadcom.com>
-- 
Florian

Re: [PATCH] net: dsa: vsc73xx: replace deprecated strncpy with ethtool_sprintf

[Vladimir Oltean]

On Mon, Oct 09, 2023 at 10:54:37PM +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.
> 
> ethtool_sprintf() is designed specifically for get_strings() usage.
> Let's replace strncpy in favor of this more robust and easier to
> understand interface.
> 
> 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/dsa/vitesse-vsc73xx-core.c | 20 ++++++--------------
>  1 file changed, 6 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/net/dsa/vitesse-vsc73xx-core.c b/drivers/net/dsa/vitesse-vsc73xx-core.c
> index 4f09e7438f3b..09955fdea2ff 100644
> --- a/drivers/net/dsa/vitesse-vsc73xx-core.c
> +++ b/drivers/net/dsa/vitesse-vsc73xx-core.c
> @@ -928,7 +928,8 @@ static void vsc73xx_get_strings(struct dsa_switch *ds, int port, u32 stringset,
>  	const struct vsc73xx_counter *cnt;
>  	struct vsc73xx *vsc = ds->priv;
>  	u8 indices[6];
> -	int i, j;
> +	u8 *buf = data;
> +	int i;
>  	u32 val;
>  	int ret;
>  
> @@ -948,10 +949,7 @@ static void vsc73xx_get_strings(struct dsa_switch *ds, int port, u32 stringset,
>  	indices[5] = ((val >> 26) & 0x1f); /* TX counter 2 */
>  
>  	/* The first counters is the RX octets */
> -	j = 0;
> -	strncpy(data + j * ETH_GSTRING_LEN,
> -		"RxEtherStatsOctets", ETH_GSTRING_LEN);
> -	j++;
> +	ethtool_sprintf(&buf, "RxEtherStatsOctets");

Here you don't use "%s", but everywhere else you do. Can't you just pass
the counter name everywhere, without "%s"?

>  
>  	/* Each port supports recording 3 RX counters and 3 TX counters,
>  	 * figure out what counters we use in this set-up and return the
> @@ -962,22 +960,16 @@ static void vsc73xx_get_strings(struct dsa_switch *ds, int port, u32 stringset,
>  	for (i = 0; i < 3; i++) {
>  		cnt = vsc73xx_find_counter(vsc, indices[i], false);
>  		if (cnt)
> -			strncpy(data + j * ETH_GSTRING_LEN,
> -				cnt->name, ETH_GSTRING_LEN);
> -		j++;
> +			ethtool_sprintf(&buf, "%s", cnt->name);

The code conversion is not functionally identical, and I think it's a
bit hard to make it identical.

The VSC7395 has 45 port counters, but it seems that it can only monitor
and display 8 of them at a time - 2 fixed and 6 configurable through
some windows.

vsc73xx_get_strings() detects which counter is each window configured
for, based on the value of the CNT_CTRL_CFG hardware register (VSC73XX_C_CFG
in the code). It displays a different string depending on the hardware
value.

The code must deal with the case where vsc73xx_find_counter() returns
NULL, aka the hardware window is configured for a value that vsc73xx_tx_counters[]
and vsc73xx_rx_counters[] don't know about.

Currently, the way that this is treated is by skipping the strncpy()
(and thus leaving an empty string), and incrementing j to get to the
next ethtool counter, and next window.

The order of the strings in vsc73xx_get_strings() needs to be strongly
correlated to the order of the counters from vsc73xx_get_ethtool_stats().
So, the driver would still print counter values for the unknown windows,
it will just not provide a string for them.

In your proposal, the increment of j basically goes into the "if (cnt)"
block because it's embedded within ethtool_sprintf(), which means that
if a hardware counter is unknown, the total number of reported strings
will be less than 8. Which is very problematic, because vsc73xx_get_sset_count()
says that 8 strings are reported. Also, all the counter strings after
the unknown one will be shifted to the left.

I suggest that "if (!cnt)", you should call ethtool_sprintf() with an
empty string, to preserve the original behavior.

>  	}
>  
>  	/* TX stats begins with the number of TX octets */
> -	strncpy(data + j * ETH_GSTRING_LEN,
> -		"TxEtherStatsOctets", ETH_GSTRING_LEN);
> -	j++;
> +	ethtool_sprintf(&buf, "TxEtherStatsOctets");
>  
>  	for (i = 3; i < 6; i++) {
>  		cnt = vsc73xx_find_counter(vsc, indices[i], true);
>  		if (cnt)
> -			strncpy(data + j * ETH_GSTRING_LEN,
> -				cnt->name, ETH_GSTRING_LEN);
> -		j++;
> +			ethtool_sprintf(&buf, "%s", cnt->name);
>  	}
>  }
>  
> 
> ---
> base-commit: cbf3a2cb156a2c911d8f38d8247814b4c07f49a2
> change-id: 20231009-strncpy-drivers-net-dsa-vitesse-vsc73xx-core-c-1cfd0ac2d81b
> 
> Best regards,
> --
> Justin Stitt <justinstitt@google.com>
> 

Re: [PATCH] net: dsa: vsc73xx: replace deprecated strncpy with ethtool_sprintf

[Justin Stitt]

On Tue, Oct 10, 2023 at 4:20 AM Vladimir Oltean <olteanv@gmail.com> wrote:
>
> On Mon, Oct 09, 2023 at 10:54:37PM +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.
> >
> > ethtool_sprintf() is designed specifically for get_strings() usage.
> > Let's replace strncpy in favor of this more robust and easier to
> > understand interface.
> >
> > 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/dsa/vitesse-vsc73xx-core.c | 20 ++++++--------------
> >  1 file changed, 6 insertions(+), 14 deletions(-)
> >
> > diff --git a/drivers/net/dsa/vitesse-vsc73xx-core.c b/drivers/net/dsa/vitesse-vsc73xx-core.c
> > index 4f09e7438f3b..09955fdea2ff 100644
> > --- a/drivers/net/dsa/vitesse-vsc73xx-core.c
> > +++ b/drivers/net/dsa/vitesse-vsc73xx-core.c
> > @@ -928,7 +928,8 @@ static void vsc73xx_get_strings(struct dsa_switch *ds, int port, u32 stringset,
> >       const struct vsc73xx_counter *cnt;
> >       struct vsc73xx *vsc = ds->priv;
> >       u8 indices[6];
> > -     int i, j;
> > +     u8 *buf = data;
> > +     int i;
> >       u32 val;
> >       int ret;
> >
> > @@ -948,10 +949,7 @@ static void vsc73xx_get_strings(struct dsa_switch *ds, int port, u32 stringset,
> >       indices[5] = ((val >> 26) & 0x1f); /* TX counter 2 */
> >
> >       /* The first counters is the RX octets */
> > -     j = 0;
> > -     strncpy(data + j * ETH_GSTRING_LEN,
> > -             "RxEtherStatsOctets", ETH_GSTRING_LEN);
> > -     j++;
> > +     ethtool_sprintf(&buf, "RxEtherStatsOctets");
>
> Here you don't use "%s", but everywhere else you do. Can't you just pass
> the counter name everywhere, without "%s"?
>
> >
> >       /* Each port supports recording 3 RX counters and 3 TX counters,
> >        * figure out what counters we use in this set-up and return the
> > @@ -962,22 +960,16 @@ static void vsc73xx_get_strings(struct dsa_switch *ds, int port, u32 stringset,
> >       for (i = 0; i < 3; i++) {
> >               cnt = vsc73xx_find_counter(vsc, indices[i], false);
> >               if (cnt)
> > -                     strncpy(data + j * ETH_GSTRING_LEN,
> > -                             cnt->name, ETH_GSTRING_LEN);
> > -             j++;
> > +                     ethtool_sprintf(&buf, "%s", cnt->name);
>
> The code conversion is not functionally identical, and I think it's a
> bit hard to make it identical.
>
> The VSC7395 has 45 port counters, but it seems that it can only monitor
> and display 8 of them at a time - 2 fixed and 6 configurable through
> some windows.
>
> vsc73xx_get_strings() detects which counter is each window configured
> for, based on the value of the CNT_CTRL_CFG hardware register (VSC73XX_C_CFG
> in the code). It displays a different string depending on the hardware
> value.
>
> The code must deal with the case where vsc73xx_find_counter() returns
> NULL, aka the hardware window is configured for a value that vsc73xx_tx_counters[]
> and vsc73xx_rx_counters[] don't know about.
>
> Currently, the way that this is treated is by skipping the strncpy()
> (and thus leaving an empty string), and incrementing j to get to the
> next ethtool counter, and next window.
>
> The order of the strings in vsc73xx_get_strings() needs to be strongly
> correlated to the order of the counters from vsc73xx_get_ethtool_stats().
> So, the driver would still print counter values for the unknown windows,
> it will just not provide a string for them.
>
> In your proposal, the increment of j basically goes into the "if (cnt)"
> block because it's embedded within ethtool_sprintf(), which means that
> if a hardware counter is unknown, the total number of reported strings
> will be less than 8. Which is very problematic, because vsc73xx_get_sset_count()
> says that 8 strings are reported. Also, all the counter strings after
> the unknown one will be shifted to the left.
>
> I suggest that "if (!cnt)", you should call ethtool_sprintf() with an
> empty string, to preserve the original behavior.

Wow, thanks for the feedback here. I agree that the current
proposal is problematic. I wonder what you think about
using a ternary to avoid smelly code dupe:

for (i = 0; i < 3; i++) {
        cnt = vsc73xx_find_counter(vsc, indices[i], false);
        ethtool_sprintf(&buf, "%s", cnt ? cnt->name : "");
}

>
> >       }
> >
> >       /* TX stats begins with the number of TX octets */
> > -     strncpy(data + j * ETH_GSTRING_LEN,
> > -             "TxEtherStatsOctets", ETH_GSTRING_LEN);
> > -     j++;
> > +     ethtool_sprintf(&buf, "TxEtherStatsOctets");
> >
> >       for (i = 3; i < 6; i++) {
> >               cnt = vsc73xx_find_counter(vsc, indices[i], true);
> >               if (cnt)
> > -                     strncpy(data + j * ETH_GSTRING_LEN,
> > -                             cnt->name, ETH_GSTRING_LEN);
> > -             j++;
> > +                     ethtool_sprintf(&buf, "%s", cnt->name);
> >       }
> >  }
> >
> >
> > ---
> > base-commit: cbf3a2cb156a2c911d8f38d8247814b4c07f49a2
> > change-id: 20231009-strncpy-drivers-net-dsa-vitesse-vsc73xx-core-c-1cfd0ac2d81b
> >
> > Best regards,
> > --
> > Justin Stitt <justinstitt@google.com>
> >
>

Thanks
Justin

Re: [PATCH] net: dsa: vsc73xx: replace deprecated strncpy with ethtool_sprintf

[Vladimir Oltean]

On Tue, Oct 10, 2023 at 10:44:42AM -0700, Justin Stitt wrote:
> Wow, thanks for the feedback here. I agree that the current
> proposal is problematic. I wonder what you think about
> using a ternary to avoid smelly code dupe:
> 
> for (i = 0; i < 3; i++) {
>         cnt = vsc73xx_find_counter(vsc, indices[i], false);
>         ethtool_sprintf(&buf, "%s", cnt ? cnt->name : "");
> }

Looks like that would address my comment, and it looks okay.

Re: [PATCH] net: dsa: vsc73xx: replace deprecated strncpy with ethtool_sprintf

[Justin Stitt]

On Tue, Oct 10, 2023 at 4:20 AM Vladimir Oltean <olteanv@gmail.com> wrote:
>
> On Mon, Oct 09, 2023 at 10:54:37PM +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.
> >
> > ethtool_sprintf() is designed specifically for get_strings() usage.
> > Let's replace strncpy in favor of this more robust and easier to
> > understand interface.
> >
> > 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/dsa/vitesse-vsc73xx-core.c | 20 ++++++--------------
> >  1 file changed, 6 insertions(+), 14 deletions(-)
> >
> > diff --git a/drivers/net/dsa/vitesse-vsc73xx-core.c b/drivers/net/dsa/vitesse-vsc73xx-core.c
> > index 4f09e7438f3b..09955fdea2ff 100644
> > --- a/drivers/net/dsa/vitesse-vsc73xx-core.c
> > +++ b/drivers/net/dsa/vitesse-vsc73xx-core.c
> > @@ -928,7 +928,8 @@ static void vsc73xx_get_strings(struct dsa_switch *ds, int port, u32 stringset,
> >       const struct vsc73xx_counter *cnt;
> >       struct vsc73xx *vsc = ds->priv;
> >       u8 indices[6];
> > -     int i, j;
> > +     u8 *buf = data;
> > +     int i;
> >       u32 val;
> >       int ret;
> >
> > @@ -948,10 +949,7 @@ static void vsc73xx_get_strings(struct dsa_switch *ds, int port, u32 stringset,
> >       indices[5] = ((val >> 26) & 0x1f); /* TX counter 2 */
> >
> >       /* The first counters is the RX octets */
> > -     j = 0;
> > -     strncpy(data + j * ETH_GSTRING_LEN,
> > -             "RxEtherStatsOctets", ETH_GSTRING_LEN);
> > -     j++;
> > +     ethtool_sprintf(&buf, "RxEtherStatsOctets");
>
> Here you don't use "%s", but everywhere else you do. Can't you just pass
> the counter name everywhere, without "%s"?

Because it's a string literal, no warning there. Maybe an argument
regarding style could be made. I have no style preference here
so I could send v2 if you feel strongly about it.

>
> >
> >       /* Each port supports recording 3 RX counters and 3 TX counters,
> >        * figure out what counters we use in this set-up and return the
> > @@ -962,22 +960,16 @@ static void vsc73xx_get_strings(struct dsa_switch *ds, int port, u32 stringset,
> >       for (i = 0; i < 3; i++) {
> >               cnt = vsc73xx_find_counter(vsc, indices[i], false);
> >               if (cnt)
> > -                     strncpy(data + j * ETH_GSTRING_LEN,
> > -                             cnt->name, ETH_GSTRING_LEN);
> > -             j++;
> > +                     ethtool_sprintf(&buf, "%s", cnt->name);
>
> The code conversion is not functionally identical, and I think it's a
> bit hard to make it identical.
>
> The VSC7395 has 45 port counters, but it seems that it can only monitor
> and display 8 of them at a time - 2 fixed and 6 configurable through
> some windows.
>
> vsc73xx_get_strings() detects which counter is each window configured
> for, based on the value of the CNT_CTRL_CFG hardware register (VSC73XX_C_CFG
> in the code). It displays a different string depending on the hardware
> value.
>
> The code must deal with the case where vsc73xx_find_counter() returns
> NULL, aka the hardware window is configured for a value that vsc73xx_tx_counters[]
> and vsc73xx_rx_counters[] don't know about.
>
> Currently, the way that this is treated is by skipping the strncpy()
> (and thus leaving an empty string), and incrementing j to get to the
> next ethtool counter, and next window.
>
> The order of the strings in vsc73xx_get_strings() needs to be strongly
> correlated to the order of the counters from vsc73xx_get_ethtool_stats().
> So, the driver would still print counter values for the unknown windows,
> it will just not provide a string for them.
>
> In your proposal, the increment of j basically goes into the "if (cnt)"
> block because it's embedded within ethtool_sprintf(), which means that
> if a hardware counter is unknown, the total number of reported strings
> will be less than 8. Which is very problematic, because vsc73xx_get_sset_count()
> says that 8 strings are reported. Also, all the counter strings after
> the unknown one will be shifted to the left.
>
> I suggest that "if (!cnt)", you should call ethtool_sprintf() with an
> empty string, to preserve the original behavior.
>
> >       }
> >
> >       /* TX stats begins with the number of TX octets */
> > -     strncpy(data + j * ETH_GSTRING_LEN,
> > -             "TxEtherStatsOctets", ETH_GSTRING_LEN);
> > -     j++;
> > +     ethtool_sprintf(&buf, "TxEtherStatsOctets");
> >
> >       for (i = 3; i < 6; i++) {
> >               cnt = vsc73xx_find_counter(vsc, indices[i], true);
> >               if (cnt)
> > -                     strncpy(data + j * ETH_GSTRING_LEN,
> > -                             cnt->name, ETH_GSTRING_LEN);
> > -             j++;
> > +                     ethtool_sprintf(&buf, "%s", cnt->name);
> >       }
> >  }
> >
> >
> > ---
> > base-commit: cbf3a2cb156a2c911d8f38d8247814b4c07f49a2
> > change-id: 20231009-strncpy-drivers-net-dsa-vitesse-vsc73xx-core-c-1cfd0ac2d81b
> >
> > Best regards,
> > --
> > Justin Stitt <justinstitt@google.com>
> >
>
Thanks
Justin

Re: [PATCH] net: dsa: vsc73xx: replace deprecated strncpy with ethtool_sprintf

[Vladimir Oltean]

On Tue, Oct 10, 2023 at 02:49:26PM -0700, Justin Stitt wrote:
> On Tue, Oct 10, 2023 at 4:20 AM Vladimir Oltean <olteanv@gmail.com> wrote:
> > Here you don't use "%s", but everywhere else you do. Can't you just pass
> > the counter name everywhere, without "%s"?
> 
> Because it's a string literal, no warning there. Maybe an argument
> regarding style could be made. I have no style preference here
> so I could send v2 if you feel strongly about it.

No, leave it alone here, don't add the "%s" where it's not needed.
But I guess you'll have to send a v2 anyway due to the other comment.