net: ieee802154: fix nl802154 add llsec key

stable inclusion
from stable-5.10.30
commit d06a96e7280351193967e48331b350cd0816b81c
bugzilla: 51791

--------------------------------

commit 20d5fe2d upstream.

This patch fixes a nullpointer dereference if NL802154_ATTR_SEC_KEY is
not set by the user. If this is the case nl802154 will return -EINVAL.

Reported-by:  <syzbot+ce4e062c2d51977ddc50@syzkaller.appspotmail.com>
Signed-off-by: Alexander Aring <aahringo@redhat.com>
Link: https://lore.kernel.org/r/20210221174321.14210-3-aahringo@redhat.com


Signed-off-by: Stefan Schmidt <stefan@datenfreihafen.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Chen Jun <chenjun102@huawei.com>
Acked-by:   Weilong Chen <chenweilong@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>