From: Kees Cook Date: Fri, 16 Feb 2024 23:31:32 +0000 (-0800) Subject: netfilter: x_tables: Use unsafe_memcpy() for 0-sized destination X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=26f4dac11775a1ca24e2605cb30e828d4dbdea93;p=linux.git netfilter: x_tables: Use unsafe_memcpy() for 0-sized destination The struct xt_entry_target fake flexible array has not be converted to a true flexible array, which is mainly blocked by it being both UAPI and used in the middle of other structures. In order to properly check for 0-sized destinations in memcpy(), an exception must be made for the one place where it is still a destination. Since memcpy() was already skipping checks for 0-sized destinations, using unsafe_memcpy() is no change in behavior. Signed-off-by: Kees Cook Reviewed-by: Simon Horman Signed-off-by: Florian Westphal --- diff --git a/net/netfilter/x_tables.c b/net/netfilter/x_tables.c index 21624d68314f9..da5d929c7c85b 100644 --- a/net/netfilter/x_tables.c +++ b/net/netfilter/x_tables.c @@ -1142,7 +1142,8 @@ void xt_compat_target_from_user(struct xt_entry_target *t, void **dstptr, if (target->compat_from_user) target->compat_from_user(t->data, ct->data); else - memcpy(t->data, ct->data, tsize - sizeof(*ct)); + unsafe_memcpy(t->data, ct->data, tsize - sizeof(*ct), + /* UAPI 0-sized destination */); tsize += off; t->u.user.target_size = tsize;