scsi: iscsi: Restrict sessions and handles to admin capabilities

stable inclusion
from linux-4.19.179
commit ae84b246a76c4ace5997e5ca7e9fde3e1a526bc3
CVE: CVE-2021-27364/CVE-2021-27363

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

commit 688e8128b7a92df982709a4137ea4588d16f24aa upstream.

Protect the iSCSI transport handle, available in sysfs, by requiring
CAP_SYS_ADMIN to read it. Also protect the netlink socket by restricting
reception of messages to ones sent with CAP_SYS_ADMIN. This disables
normal users from being able to end arbitrary iSCSI sessions.

Cc: stable@vger.kernel.org
Reported-by: Adam Nichols <adam@grimm-co.com>
Reviewed-by: Chris Leech <cleech@redhat.com>
Reviewed-by: Mike Christie <michael.christie@oracle.com>
Signed-off-by: Lee Duncan <lduncan@suse.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Reviewed-by: Xiu Jianfeng <xiujianfeng@huawei.com>
Reviewed-by: Yufen Yu <yuyufen@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Signed-off-by: Cheng Jian <cj.chengjian@huawei.com>

drivers/scsi/scsi_transport_iscsi.c

@@ -119,6 +119,9 @@ show_transport_handle(struct device *dev, struct device_attribute *attr,
 		      char *buf)
 {
 	struct iscsi_internal *priv = dev_to_iscsi_internal(dev);
+
+	if (!capable(CAP_SYS_ADMIN))
+		return -EACCES;
 	return sprintf(buf, "%llu\n", (unsigned long long)iscsi_handle(priv->iscsi_transport));
 }
 static DEVICE_ATTR(handle, S_IRUGO, show_transport_handle, NULL);
@@ -3504,6 +3507,9 @@ iscsi_if_recv_msg(struct sk_buff *skb, struct nlmsghdr *nlh, uint32_t *group)
 	struct iscsi_cls_conn *conn;
 	struct iscsi_endpoint *ep = NULL;
 
+	if (!netlink_capable(skb, CAP_SYS_ADMIN))
+		return -EPERM;
+
 	if (nlh->nlmsg_type == ISCSI_UEVENT_PATH_UPDATE)
 		*group = ISCSI_NL_GRP_UIP;
 	else