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SubjectRe: [PATCH v2] net: bonding: Use strscpy() instead of manually-truncated strncpy()
Date
Kees Cook <keescook@chromium.org> wrote:

>Silence this warning by just using strscpy_pad() 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);
> | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
>Additionally replace other strncpy() uses, as it is considered deprecated:
>https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings
>
>Reported-by: kernel test robot <lkp@intel.com>
>Link: https://lore.kernel.org/lkml/202102150705.fdR6obB0-lkp@intel.com
>Signed-off-by: Kees Cook <keescook@chromium.org>

There's one more "strncpy(...); primary[IFNAMSIZ - 1] = 0;" set
in bond_options.c:bond_option_primary_set(), doesn't it also generate
this warning?

Either way, the change looks good to me.

Acked-by: Jay Vosburgh <jay.vosburgh@canonical.com>

-J


>---
>v2:
> - switch to strscpy_pad() and replace earlier strncpy() too
>v1: https://lore.kernel.org/lkml/20210602181133.3326856-1-keescook@chromium.org
>---
> drivers/net/bonding/bond_main.c | 8 +++-----
> 1 file changed, 3 insertions(+), 5 deletions(-)
>
>diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
>index c5a646d06102..e9cb716ad849 100644
>--- a/drivers/net/bonding/bond_main.c
>+++ b/drivers/net/bonding/bond_main.c
>@@ -620,7 +620,7 @@ static int bond_check_dev_link(struct bonding *bond,
> */
>
> /* Yes, the mii is overlaid on the ifreq.ifr_ifru */
>- strncpy(ifr.ifr_name, slave_dev->name, IFNAMSIZ);
>+ strscpy_pad(ifr.ifr_name, slave_dev->name, IFNAMSIZ);
> mii = if_mii(&ifr);
> if (ioctl(slave_dev, &ifr, SIOCGMIIPHY) == 0) {
> mii->reg_num = MII_BMSR;
>@@ -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_pad(params->primary, primary, sizeof(params->primary));
>
> memcpy(params->arp_targets, arp_target, sizeof(arp_target));
>
>--
>2.25.1

---
-Jay Vosburgh, jay.vosburgh@canonical.com

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