| Message ID | 20231012-strncpy-drivers-net-phy-mdio_bus-c-v1-1-15242e6f9ec4@google.com (mailing list archive) |
|---|---|
| State | Changes Requested |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | net: mdio: replace deprecated strncpy with strscpy | expand |
On Thu, Oct 12, 2023 at 09:53:03PM +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. Hi Justin You just sent two patches with the same Subject. That got me confused for a while, is it a resend? A new version? > 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: Andrew Lunn <andrew@lunn.ch> Andrew
On Thu, Oct 12, 2023 at 2:59 PM Andrew Lunn <andrew@lunn.ch> wrote: > > On Thu, Oct 12, 2023 at 09:53:03PM +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. > > Hi Justin > > You just sent two patches with the same Subject. That got me confused > for a while, is it a resend? A new version? Yep, just saw this. I'm working (top to bottom) on a list of strncpy hits. I have an automated tool fetch the prefix and update the subject line accordingly. They are two separate patches but ended up with the same exact subject line due to oversight and over-automation. Looking for guidance: Should I combine them into one patch? > > > 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: Andrew Lunn <andrew@lunn.ch> > > Andrew > Thanks Justin
On Thu, Oct 12, 2023 at 03:01:06PM -0700, Justin Stitt wrote: > On Thu, Oct 12, 2023 at 2:59 PM Andrew Lunn <andrew@lunn.ch> wrote: > > > > On Thu, Oct 12, 2023 at 09:53:03PM +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. > > > > Hi Justin > > > > You just sent two patches with the same Subject. That got me confused > > for a while, is it a resend? A new version? > > Yep, just saw this. > > I'm working (top to bottom) on a list of strncpy hits. I have an automated tool > fetch the prefix and update the subject line accordingly. They are two separate > patches but ended up with the same exact subject line due to oversight and > over-automation. > > Looking for guidance: > Should I combine them into one patch? No, it is fine. Just try to avoid it in the future. Andrew
On Thu, Oct 12, 2023 at 09:53:03PM +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. > > We expect mdiodev->modalias to be NUL-terminated based on its usage with > strcmp(): > | return strcmp(mdiodev->modalias, drv->name) == 0; > > Moreover, mdiodev->modalias is already zero-allocated: > | mdiodev = kzalloc(sizeof(*mdiodev), GFP_KERNEL); > ... which means the NUL-padding strncpy provides is not necessary. > > 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 good! Reviewed-by: Kees Cook <keescook@chromium.org>
diff --git a/drivers/net/phy/mdio_bus.c b/drivers/net/phy/mdio_bus.c index 25dcaa49ab8b..6cf73c15635b 100644 --- a/drivers/net/phy/mdio_bus.c +++ b/drivers/net/phy/mdio_bus.c @@ -506,7 +506,7 @@ static int mdiobus_create_device(struct mii_bus *bus, if (IS_ERR(mdiodev)) return -ENODEV; - strncpy(mdiodev->modalias, bi->modalias, + strscpy(mdiodev->modalias, bi->modalias, sizeof(mdiodev->modalias)); mdiodev->bus_match = mdio_device_bus_match; mdiodev->dev.platform_data = (void *)bi->platform_data;
strncpy() is deprecated for use on NUL-terminated destination strings [1] and as such we should prefer more robust and less ambiguous string interfaces. We expect mdiodev->modalias to be NUL-terminated based on its usage with strcmp(): | return strcmp(mdiodev->modalias, drv->name) == 0; Moreover, mdiodev->modalias is already zero-allocated: | mdiodev = kzalloc(sizeof(*mdiodev), GFP_KERNEL); ... which means the NUL-padding strncpy provides is not necessary. 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/phy/mdio_bus.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- base-commit: cbf3a2cb156a2c911d8f38d8247814b4c07f49a2 change-id: 20231012-strncpy-drivers-net-phy-mdio_bus-c-0a0d5e875712 Best regards, -- Justin Stitt <justinstitt@google.com>