Commit message: scsi: libsas: stop discovering if oob mode is disconnected

The discovering of sas port is driven by workqueue in libsas. When libsas
is processing port events or phy events in workqueue, new events may rise
up and change the state of some structures such as asd_sas_phy.  This may
cause some problems such as follows:

==>thread 1                       ==>thread 2

                                  ==>phy up
                                  ==>phy_up_v3_hw()
                                    ==>oob_mode = SATA_OOB_MODE;
                                  ==>phy down quickly
                                  ==>hisi_sas_phy_down()
                                    ==>sas_ha->notify_phy_event()
                                    ==>sas_phy_disconnected()
                                      ==>oob_mode = OOB_NOT_CONNECTED
==>workqueue wakeup
==>sas_form_port()
  ==>sas_discover_domain()
    ==>sas_get_port_device()
      ==>oob_mode is OOB_NOT_CONNECTED and device
         is wrongly taken as expander

This at last lead to the panic when libsas trying to issue a command to
discover the device.

[183047.614035] Unable to handle kernel NULL pointer dereference at
virtual address 0000000000000058
[183047.622896] Mem abort info:
[183047.625762]   ESR = 0x96000004
[183047.628893]   Exception class = DABT (current EL), IL = 32 bits
[183047.634888]   SET = 0, FnV = 0
[183047.638015]   EA = 0, S1PTW = 0
[183047.641232] Data abort info:
[183047.644189]   ISV = 0, ISS = 0x00000004
[183047.648100]   CM = 0, WnR = 0
[183047.651145] user pgtable: 4k pages, 48-bit VAs, pgdp =
00000000b7df67be
[183047.657834] [0000000000000058] pgd=0000000000000000
[183047.662789] Internal error: Oops: 96000004 [#1] SMP
[183047.667740] Process kworker/u16:2 (pid: 31291, stack limit =
0x00000000417c4974)
[183047.675208] CPU: 0 PID: 3291 Comm: kworker/u16:2 Tainted: G
W  OE 4.19.36-vhulk1907.1.0.h410.eulerosv2r8.aarch64 #1
[183047.687015] Hardware name: N/A N/A/Kunpeng Desktop Board D920S10,
BIOS 0.15 10/22/2019
[183047.695007] Workqueue: 0000:74:02.0_disco_q sas_discover_domain
[183047.700999] pstate: 20c00009 (nzCv daif +PAN +UAO)
[183047.705864] pc : prep_ata_v3_hw+0xf8/0x230 [hisi_sas_v3_hw]
[183047.711510] lr : prep_ata_v3_hw+0xb0/0x230 [hisi_sas_v3_hw]
[183047.717153] sp : ffff00000f28ba60
[183047.720541] x29: ffff00000f28ba60 x28: ffff8026852d7228
[183047.725925] x27: ffff8027dba3e0a8 x26: ffff8027c05fc200
[183047.731310] x25: 0000000000000000 x24: ffff8026bafa8dc0
[183047.736695] x23: ffff8027c05fc218 x22: ffff8026852d7228
[183047.742079] x21: ffff80007c2f2940 x20: ffff8027c05fc200
[183047.747464] x19: 0000000000f80800 x18: 0000000000000010
[183047.752848] x17: 0000000000000000 x16: 0000000000000000
[183047.758232] x15: ffff000089a5a4ff x14: 0000000000000005
[183047.763617] x13: ffff000009a5a50e x12: ffff8026bafa1e20
[183047.769001] x11: ffff0000087453b8 x10: ffff00000f28b870
[183047.774385] x9 : 0000000000000000 x8 : ffff80007e58f9b0
[183047.779770] x7 : 0000000000000000 x6 : 000000000000003f
[183047.785154] x5 : 0000000000000040 x4 : ffffffffffffffe0
[183047.790538] x3 : 00000000000000f8 x2 : 0000000002000007
[183047.795922] x1 : 0000000000000008 x0 : 0000000000000000
[183047.801307] Call trace:
[183047.803827]  prep_ata_v3_hw+0xf8/0x230 [hisi_sas_v3_hw]
[183047.809127]  hisi_sas_task_prep+0x750/0x888 [hisi_sas_main]
[183047.814773]  hisi_sas_task_exec.isra.7+0x88/0x1f0 [hisi_sas_main]
[183047.820939]  hisi_sas_queue_command+0x28/0x38 [hisi_sas_main]
[183047.826757]  smp_execute_task_sg+0xec/0x218
[183047.831013]  smp_execute_task+0x74/0xa0
[183047.834921]  sas_discover_expander.part.7+0x9c/0x5f8
[183047.839959]  sas_discover_root_expander+0x90/0x160
[183047.844822]  sas_discover_domain+0x1b8/0x1e8
[183047.849164]  process_one_work+0x1b4/0x3f8
[183047.853246]  worker_thread+0x54/0x470
[183047.856981]  kthread+0x134/0x138
[183047.860283]  ret_from_fork+0x10/0x18
[183047.863931] Code: f9407a80 528000e2 39409281 72a04002 (b9405800)
[183047.870097] kernel fault(0x1) notification starting on CPU 0
[183047.875828] kernel fault(0x1) notification finished on CPU 0
[183047.881559] Modules linked in: unibsp(OE) hns3(OE) hclge(OE)
hnae3(OE) mem_drv(OE) hisi_sas_v3_hw(OE) hisi_sas_main(OE)
[183047.892418] ---[ end trace 4cc26083fc11b783  ]---
[183047.897107] Kernel panic - not syncing: Fatal exception
[183047.902403] kernel fault(0x5) notification starting on CPU 0
[183047.908134] kernel fault(0x5) notification finished on CPU 0
[183047.913865] SMP: stopping secondary CPUs
[183047.917861] Kernel Offset: disabled
[183047.921422] CPU features: 0x2,a2a00a38
[183047.925243] Memory Limit: none
[183047.928372] kernel reboot(0x2) notification starting on CPU 0
[183047.934190] kernel reboot(0x2) notification finished on CPU 0
[183047.940008] ---[ end Kernel panic - not syncing: Fatal exception
]---

Fixes: 2908d778ab3e ("[SCSI] aic94xx: new driver")
Link: https://lore.kernel.org/r/20191206011118.46909-1-yanaijie@huawei.com
Reported-by: Gao Chuan <gaochuan4@huawei.com>
Reviewed-by: John Garry <john.garry@huawei.com>
Signed-off-by: Jason Yan <yanaijie@huawei.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
CVE: CVE-2019-19965
CWE: CWE-476
Vulnerability description: In the Linux kernel through 5.4.6, there is a NULL pointer dereference in drivers/scsi/libsas/sas_discover.c because of mishandling of port disconnection during discovery, related to a PHY down race condition, aka CID-f70267f379b5.

Project: linux
File: sas_discover.c

static int sas_get_port_device(struct asd_sas_port *port)
{
	struct asd_sas_phy *phy;
	struct sas_rphy *rphy;
	struct domain_device *dev;
	int rc = -ENODEV;

	dev = sas_alloc_device();
	if (!dev)
		return -ENOMEM;

	spin_lock_irq(&port->phy_list_lock);
	if (list_empty(&port->phy_list)) {
		spin_unlock_irq(&port->phy_list_lock);
		sas_put_device(dev);
		return -ENODEV;
	}
	phy = container_of(port->phy_list.next, struct asd_sas_phy, port_phy_el);
	spin_lock(&phy->frame_rcvd_lock);
	memcpy(dev->frame_rcvd, phy->frame_rcvd, min(sizeof(dev->frame_rcvd),
					     (size_t)phy->frame_rcvd_size));
	spin_unlock(&phy->frame_rcvd_lock);
	spin_unlock_irq(&port->phy_list_lock);

	if (dev->frame_rcvd[0] == 0x34 && port->oob_mode == SATA_OOB_MODE) {
		struct dev_to_host_fis *fis =
			(struct dev_to_host_fis *) dev->frame_rcvd;
		if (fis->interrupt_reason == 1 && fis->lbal == 1 &&
		    fis->byte_count_low==0x69 && fis->byte_count_high == 0x96
		    && (fis->device & ~0x10) == 0)
			dev->dev_type = SAS_SATA_PM;
		else
			dev->dev_type = SAS_SATA_DEV;
		dev->tproto = SAS_PROTOCOL_SATA;
	} else {
		struct sas_identify_frame *id =
			(struct sas_identify_frame *) dev->frame_rcvd;
		dev->dev_type = id->dev_type;
		dev->iproto = id->initiator_bits;
		dev->tproto = id->target_bits;
	}

	sas_init_dev(dev);

	dev->port = port;
	switch (dev->dev_type) {
	case SAS_SATA_DEV:
		rc = sas_ata_init(dev);
		if (rc) {
			rphy = NULL;
			break;
		}
		/* fall through */
	case SAS_END_DEVICE:
		rphy = sas_end_device_alloc(port->port);
		break;
	case SAS_EDGE_EXPANDER_DEVICE:
		rphy = sas_expander_alloc(port->port,
					  SAS_EDGE_EXPANDER_DEVICE);
		break;
	case SAS_FANOUT_EXPANDER_DEVICE:
		rphy = sas_expander_alloc(port->port,
					  SAS_FANOUT_EXPANDER_DEVICE);
		break;
	default:
		pr_warn("ERROR: Unidentified device type %d\n", dev->dev_type);
		rphy = NULL;
		break;
	}

	if (!rphy) {
		sas_put_device(dev);
		return rc;
	}

	rphy->identify.phy_identifier = phy->phy->identify.phy_identifier;
	memcpy(dev->sas_addr, port->attached_sas_addr, SAS_ADDR_SIZE);
	sas_fill_in_rphy(dev, rphy);
	sas_hash_addr(dev->hashed_sas_addr, dev->sas_addr);
	port->port_dev = dev;
	dev->linkrate = port->linkrate;
	dev->min_linkrate = port->linkrate;
	dev->max_linkrate = port->linkrate;
	dev->pathways = port->num_phys;
	memset(port->disc.fanout_sas_addr, 0, SAS_ADDR_SIZE);
	memset(port->disc.eeds_a, 0, SAS_ADDR_SIZE);
	memset(port->disc.eeds_b, 0, SAS_ADDR_SIZE);
	port->disc.max_level = 0;
	sas_device_set_phy(dev, port->port);

	dev->rphy = rphy;
	get_device(&dev->rphy->dev);

	if (dev_is_sata(dev) || dev->dev_type == SAS_END_DEVICE)
		list_add_tail(&dev->disco_list_node, &port->disco_list);
	else {
		spin_lock_irq(&port->dev_list_lock);
		list_add_tail(&dev->dev_list_node, &port->dev_list);
		spin_unlock_irq(&port->dev_list_lock);
	}

	spin_lock_irq(&port->phy_list_lock);
	list_for_each_entry(phy, &port->phy_list, port_phy_el)
		sas_phy_set_target(phy, dev);
	spin_unlock_irq(&port->phy_list_lock);

	return 0;
}