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 <keescook@xxxxxxxxxxxx> --- Cc: Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx> Cc: Jozsef Kadlecsik <kadlec@xxxxxxxxxxxxx> Cc: Florian Westphal <fw@xxxxxxxxx> Cc: "David S. Miller" <davem@xxxxxxxxxxxxx> Cc: Eric Dumazet <edumazet@xxxxxxxxxx> Cc: Jakub Kicinski <kuba@xxxxxxxxxx> Cc: Paolo Abeni <pabeni@xxxxxxxxxx> Cc: Gustavo A. R. Silva <gustavo@xxxxxxxxxxxxxx> Cc: netfilter-devel@xxxxxxxxxxxxxxx Cc: coreteam@xxxxxxxxxxxxx Cc: netdev@xxxxxxxxxxxxxxx --- net/netfilter/x_tables.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/net/netfilter/x_tables.c b/net/netfilter/x_tables.c index 21624d68314f..da5d929c7c85 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; -- 2.34.1
