Messages in this thread Patch in this message | | | Date | Tue, 10 Oct 2023 14:20:51 +0300 | From | Vladimir Oltean <> | Subject | Re: [PATCH] net: dsa: vsc73xx: replace deprecated strncpy with ethtool_sprintf |
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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> >
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