`strncpy` is deprecated for use on NUL-terminated destination strings [1].
A suitable replacement is `strscpy` [2] due to the fact that it
guarantees NUL-termination on its destination buffer argument which is
_not_ the case for `strncpy`!
In this case, we are able to drop the now superfluous `... - 1`
instances because `strscpy` will automatically truncate the last byte by
setting it to a NUL byte if the source size exceeds the destination size
or if the source string is not NUL-terminated.
I've also opted to remove the seemingly useless char* casts. I'm not
sure why they're present at all since (after expanding the `ifr_name`
macro) `ifr.ifr_ifrn.ifrn_name` is a char* already.
All in all, `strscpy` is a more robust and less ambiguous interface
while also letting us remove some `... -1`'s which cleans things up a
bit.
[1]: http://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings
[2]: https://manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html
Link: https://github.com/KSPP/linux/issues/90
Cc: [email protected]
Signed-off-by: Justin Stitt <[email protected]>
---
arch/um/drivers/vector_user.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/arch/um/drivers/vector_user.c b/arch/um/drivers/vector_user.c
index c650e428432b..c719e1ec4645 100644
--- a/arch/um/drivers/vector_user.c
+++ b/arch/um/drivers/vector_user.c
@@ -141,7 +141,7 @@ static int create_tap_fd(char *iface)
}
memset(&ifr, 0, sizeof(ifr));
ifr.ifr_flags = IFF_TAP | IFF_NO_PI | IFF_VNET_HDR;
- strncpy((char *)&ifr.ifr_name, iface, sizeof(ifr.ifr_name) - 1);
+ strscpy(ifr.ifr_name, iface, sizeof(ifr.ifr_name));
err = ioctl(fd, TUNSETIFF, (void *) &ifr);
if (err != 0) {
@@ -171,7 +171,7 @@ static int create_raw_fd(char *iface, int flags, int proto)
goto raw_fd_cleanup;
}
memset(&ifr, 0, sizeof(ifr));
- strncpy((char *)&ifr.ifr_name, iface, sizeof(ifr.ifr_name) - 1);
+ strscpy(ifr.ifr_name, iface, sizeof(ifr.ifr_name));
if (ioctl(fd, SIOCGIFINDEX, (void *) &ifr) < 0) {
err = -errno;
goto raw_fd_cleanup;
---
base-commit: c1a515d3c0270628df8ae5f5118ba859b85464a2
change-id: 20230807-arch-um-drivers-ad44050885d0
Best regards,
--
Justin Stitt <[email protected]>
On 07/08/2023 19:22, Justin Stitt wrote:
> `strncpy` is deprecated for use on NUL-terminated destination strings [1].
>
> A suitable replacement is `strscpy` [2] due to the fact that it
> guarantees NUL-termination on its destination buffer argument which is
> _not_ the case for `strncpy`!
>
> In this case, we are able to drop the now superfluous `... - 1`
> instances because `strscpy` will automatically truncate the last byte by
> setting it to a NUL byte if the source size exceeds the destination size
> or if the source string is not NUL-terminated.
>
> I've also opted to remove the seemingly useless char* casts. I'm not
> sure why they're present at all since (after expanding the `ifr_name`
> macro) `ifr.ifr_ifrn.ifrn_name` is a char* already.
>
> All in all, `strscpy` is a more robust and less ambiguous interface
> while also letting us remove some `... -1`'s which cleans things up a
> bit.
>
> [1]: http://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings
> [2]: https://manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html
>
> Link: https://github.com/KSPP/linux/issues/90
> Cc: [email protected]
> Signed-off-by: Justin Stitt <[email protected]>
> ---
> arch/um/drivers/vector_user.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/arch/um/drivers/vector_user.c b/arch/um/drivers/vector_user.c
> index c650e428432b..c719e1ec4645 100644
> --- a/arch/um/drivers/vector_user.c
> +++ b/arch/um/drivers/vector_user.c
> @@ -141,7 +141,7 @@ static int create_tap_fd(char *iface)
> }
> memset(&ifr, 0, sizeof(ifr));
> ifr.ifr_flags = IFF_TAP | IFF_NO_PI | IFF_VNET_HDR;
> - strncpy((char *)&ifr.ifr_name, iface, sizeof(ifr.ifr_name) - 1);
> + strscpy(ifr.ifr_name, iface, sizeof(ifr.ifr_name));
>
> err = ioctl(fd, TUNSETIFF, (void *) &ifr);
> if (err != 0) {
> @@ -171,7 +171,7 @@ static int create_raw_fd(char *iface, int flags, int proto)
> goto raw_fd_cleanup;
> }
> memset(&ifr, 0, sizeof(ifr));
> - strncpy((char *)&ifr.ifr_name, iface, sizeof(ifr.ifr_name) - 1);
> + strscpy(ifr.ifr_name, iface, sizeof(ifr.ifr_name));
> if (ioctl(fd, SIOCGIFINDEX, (void *) &ifr) < 0) {
> err = -errno;
> goto raw_fd_cleanup;
>
> ---
> base-commit: c1a515d3c0270628df8ae5f5118ba859b85464a2
> change-id: 20230807-arch-um-drivers-ad44050885d0
>
> Best regards,
> --
> Justin Stitt <[email protected]>
>
>
> _______________________________________________
> linux-um mailing list
> [email protected]
> http://lists.infradead.org/mailman/listinfo/linux-um
>
Acked-by: Anton Ivanov <[email protected]>
--
Anton R. Ivanov
Cambridgegreys Limited. Registered in England. Company Number 10273661
https://www.cambridgegreys.com/
On Mon, 07 Aug 2023 18:22:30 +0000, Justin Stitt wrote:
> `strncpy` is deprecated for use on NUL-terminated destination strings [1].
>
> A suitable replacement is `strscpy` [2] due to the fact that it
> guarantees NUL-termination on its destination buffer argument which is
> _not_ the case for `strncpy`!
>
> In this case, we are able to drop the now superfluous `... - 1`
> instances because `strscpy` will automatically truncate the last byte by
> setting it to a NUL byte if the source size exceeds the destination size
> or if the source string is not NUL-terminated.
>
> [...]
Applied to for-next/hardening, thanks!
[1/1] um: vector: refactor deprecated strncpy
https://git.kernel.org/kees/c/30bed99e0c63
Take care,
--
Kees Cook