2021-06-02 18:14:06

by Kees Cook

Subject: [PATCH] net: bonding: Use strscpy() instead of manually-truncated strncpy()

Silence this warning by just using strscpy() directly:

drivers/net/bonding/bond_main.c:4877:3: warning: 'strncpy' specified bound 16 equals destination size [-Wstringop-truncation]
4877 | strncpy(params->primary, primary, IFNAMSIZ);
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Reported-by: kernel test robot <[email protected]>
Link: https://lore.kernel.org/lkml/[email protected]
Signed-off-by: Kees Cook <[email protected]>
---
drivers/net/bonding/bond_main.c | 6 ++----
1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index c5a646d06102..ecfc48f2d0d0 100644
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -5329,10 +5329,8 @@ static int bond_check_params(struct bond_params *params)
(struct reciprocal_value) { 0 };
}

- if (primary) {
- strncpy(params->primary, primary, IFNAMSIZ);
- params->primary[IFNAMSIZ - 1] = 0;
- }
+ if (primary)
+ strscpy(params->primary, primary, sizeof(params->primary));

memcpy(params->arp_targets, arp_target, sizeof(arp_target));

--
2.25.1

2021-06-02 19:50:34

by Shoaib Rao

Subject: Re: [PATCH] net: bonding: Use strscpy() instead of manually-truncated strncpy()

Would it make sense to also replace the other strncpy in the same file.

Shoaib

On 6/2/21 11:11 AM, Kees Cook wrote:
> Silence this warning by just using strscpy() directly:
>
> drivers/net/bonding/bond_main.c:4877:3: warning: 'strncpy' specified bound 16 equals destination size [-Wstringop-truncation]
> 4877 | strncpy(params->primary, primary, IFNAMSIZ);
> | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> Reported-by: kernel test robot <[email protected]>
> Link: https://lore.kernel.org/lkml/[email protected]
> Signed-off-by: Kees Cook <[email protected]>
> ---
> drivers/net/bonding/bond_main.c | 6 ++----
> 1 file changed, 2 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
> index c5a646d06102..ecfc48f2d0d0 100644
> --- a/drivers/net/bonding/bond_main.c
> +++ b/drivers/net/bonding/bond_main.c
> @@ -5329,10 +5329,8 @@ static int bond_check_params(struct bond_params *params)
> (struct reciprocal_value) { 0 };
> }
>
> - if (primary) {
> - strncpy(params->primary, primary, IFNAMSIZ);
> - params->primary[IFNAMSIZ - 1] = 0;
> - }
> + if (primary)
> + strscpy(params->primary, primary, sizeof(params->primary));
>
> memcpy(params->arp_targets, arp_target, sizeof(arp_target));
>

2021-06-02 20:06:06

by Kees Cook

Subject: Re: [PATCH] net: bonding: Use strscpy() instead of manually-truncated strncpy()

On Wed, Jun 02, 2021 at 12:46:46PM -0700, Rao Shoaib wrote:
> Would it make sense to also replace the other strncpy in the same file.

strncpy(ifr.ifr_name, slave_dev->name, IFNAMSIZ);

I couldn't tell if this was a non-string, if it needed padding, etc. The
one I fixed below appears to be null-terminated? (Though now that I look
at it, perhaps it should be using strscpy_pad().)

And there are a bunch of other manual truncations in the kernel on
ifr_name:

$ git grep ifr_name | grep 'IFNAMSIZ.*=.*0'
drivers/net/tun.c: ifr.ifr_name[IFNAMSIZ-1] = '\0';
net/core/dev_ioctl.c: ifr->ifr_name[IFNAMSIZ-1] = 0;
net/core/dev_ioctl.c: ifr->ifr_name[IFNAMSIZ-1] = 0;
net/decnet/dn_dev.c: ifr->ifr_name[IFNAMSIZ-1] = 0;
net/ieee802154/socket.c: ifr.ifr_name[IFNAMSIZ-1] = 0;
net/ipv4/devinet.c: ifr->ifr_name[IFNAMSIZ - 1] = 0;
net/wireless/wext-core.c: iwr.ifr_name[IFNAMSIZ-1] = 0;
tools/lib/bpf/xsk.c: ifr.ifr_name[IFNAMSIZ - 1] = '\0';

And given the copy_to_user() that might happen, I think this should
absolutely be strscpy_pad(). I will send a v2...

-Kees

>
> Shoaib
>
> On 6/2/21 11:11 AM, Kees Cook wrote:
> > Silence this warning by just using strscpy() directly:
> >
> > drivers/net/bonding/bond_main.c:4877:3: warning: 'strncpy' specified bound 16 equals destination size [-Wstringop-truncation]
> > 4877 | strncpy(params->primary, primary, IFNAMSIZ);
> > | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> >
> > Reported-by: kernel test robot <[email protected]>
> > Link: https://lore.kernel.org/lkml/[email protected]
> > Signed-off-by: Kees Cook <[email protected]>
> > ---
> > drivers/net/bonding/bond_main.c | 6 ++----
> > 1 file changed, 2 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
> > index c5a646d06102..ecfc48f2d0d0 100644
> > --- a/drivers/net/bonding/bond_main.c
> > +++ b/drivers/net/bonding/bond_main.c
> > @@ -5329,10 +5329,8 @@ static int bond_check_params(struct bond_params *params)
> > (struct reciprocal_value) { 0 };
> > }
> > - if (primary) {
> > - strncpy(params->primary, primary, IFNAMSIZ);
> > - params->primary[IFNAMSIZ - 1] = 0;
> > - }
> > + if (primary)
> > + strscpy(params->primary, primary, sizeof(params->primary));
> > memcpy(params->arp_targets, arp_target, sizeof(arp_target));

--
Kees Cook