Re: [PATCH v1] driver core: Use list_del_init to replace list_del at device_links_purge()

[James Bottomley]

On Wed, 2020-01-08 at 14:50 +0000, John Garry wrote:
> On 08/01/2020 12:26, Greg KH wrote:
> > On Wed, Jan 08, 2020 at 07:34:04PM +0800, Luo Jiaxing wrote:
> > > We found that enabling kernel compilation options
> > > CONFIG_SCSI_ENCLOSURE and
> > > CONFIG_ENCLOSURE_SERVICES, repeated initialization and deletion
> > > of the same
> > > SCSI device will cause system panic, as follows:
> > > [72.425705] Unable to handle kernel paging request at virtual
> > > address
> > > dead000000000108
> > > ...
> > > [72.595093] Call trace:
> > > [72.597532] device_del + 0x194 / 0x3a0
> > > [72.601012] enclosure_remove_device + 0xbc / 0xf8
> > > [72.605445] ses_intf_remove + 0x9c / 0xd8
> > > [72.609185] device_del + 0xf8 / 0x3a0
> > > [72.612576] device_unregister + 0x14 / 0x30
> > > [72.616489] __scsi_remove_device + 0xf4 / 0x140
> > > [72.620747] scsi_remove_device + 0x28 / 0x40
> > > [72.624745] scsi_remove_target + 0x1c8 / 0x220
> > > 
> > > After analysis, we see that in the error scenario, the ses module
> > > has the
> > > following calling sequence:
> > > device_register() -> device_del() -> device_add() ->
> > > device_del().
> > > The first call to device_del() is fine, but the second call to
> > > device_del()
> > > will cause a system panic.
> > 
> > Is this all on the same device structure?  If so, that's not ok,
> > you
> > can't do that, once device_del() is called on the memory location,
> > you
> > can not call device_add() on it again.
> > 
> > How are you triggering this from userspace?
> 
> This can be triggered by causing the SCSI device to be lost, found,
> and 
> lost again:
> 
> root@(none)$ pwd
> /sys/class/sas_phy/phy-0:0:2
> root@(none)$ echo 0 > enable
> [   48.828139] sas: smp_execute_task_sg: task to dev
> 500e004aaaaaaa1f 
> response: 0x0 status 0x2
> root@(none)$
> [   48.837040] sas: ex 500e004aaaaaaa1f phy02 change count has
> changed
> [   48.846961] sd 0:0:0:0: [sda] Synchronizing SCSI cache
> [   48.852120] sd 0:0:0:0: [sda] Synchronize Cache(10) failed:
> Result: 
> hostbyte=0x04 driverbyte=0x00
> [   48.898111] hisi_sas_v3_hw 0000:74:02.0: dev[2:1] is gone
> 
> root@(none)$ echo 1 > enable
> root@(none)$
> [   51.967416] sas: ex 500e004aaaaaaa1f phy02 change count has
> changed
> [   51.974022] hisi_sas_v3_hw 0000:74:02.0: dev[7:1] found
> [   51.991305] scsi 0:0:5:0: Direct-Access     SEAGATE  ST2000NM0045 
> N004 PQ: 0 ANSI: 6
> [   52.003609] sd 0:0:5:0: [sda] 3907029168 512-byte logical blocks: 
> (2.00 TB/1.82 TiB)
> [   52.012010] sd 0:0:5:0: [sda] Write Protect is off
> [   52.022643] sd 0:0:5:0: [sda] Write cache: enabled, read cache: 
> enabled, supports DPO and FUA
> [   52.052429]  sda: sda1
> [   52.064439] sd 0:0:5:0: [sda] Attached SCSI disk
> 
> root@(none)$ echo 0 > enable
> [   54.112100] sas: smp_execute_task_sg: task to dev
> 500e004aaaaaaa1f 
> response: 0x0 status 0x2
> root@(none)$ [   54.120909] sas: ex 500e004aaaaaaa1f phy02 change
> count 
> has changed
> [   54.130202] Unable to handle kernel paging request at virtual
> address 
> dead000000000108
> [   54.138110] Mem abort info:
> [   54.140892]   ESR = 0x96000044
> [   54.143936]   EC = 0x25: DABT (current EL), IL = 32 bits
> [   54.149236]   SET = 0, FnV = 0
> [   54.152278]   EA = 0, S1PTW = 0
> [   54.155408] Data abort info:
> [   54.158275]   ISV = 0, ISS = 0x00000044
> [   54.162098]   CM = 0, WnR = 1
> [   54.165055] [dead000000000108] address between user and kernel 
> address ranges
> [   54.172179] Internal error: Oops: 96000044 [#1] PREEMPT SMP
> [   54.177737] Modules linked in:
> [   54.180780] CPU: 5 PID: 741 Comm: kworker/u192:2 Not tainted 
> 5.5.0-rc5-dirty #1535
> [   54.188334] Hardware name: Huawei D06 /D06, BIOS Hisilicon D06
> UEFI 
> RC0 - V1.16.01 03/15/2019
> [   54.196847] Workqueue: 0000:74:02.0_disco_q sas_revalidate_domain
> [   54.202927] pstate: 60c00009 (nZCv daif +PAN +UAO)
> [   54.207705] pc : device_del+0x194/0x398
> [   54.211527] lr : device_del+0x190/0x398
> [   54.215349] sp : ffff80001cc7bb20
> [   54.218650] x29: ffff80001cc7bb20 x28: ffff0023be042188
> [   54.223948] x27: ffff0023c04c0000 x26: ffff0023be042000
> [   54.229246] x25: ffff8000119f0f30 x24: ffff0023be268a30
> [   54.234544] x23: ffff0023be268018 x22: ffff800011879000
> [   54.239842] x21: ffff8000119f0000 x20: ffff8000119f06e0
> [   54.245140] x19: ffff0023be268990 x18: 0000000000000004
> [   54.250438] x17: 0000000000000007 x16: 0000000000000001
> [   54.255736] x15: ffff0023eac13610 x14: ffff0023eb74a7f8
> [   54.261034] x13: 0000000000000000 x12: ffff0023eac13610
> [   54.266332] x11: ffff0023eb74a6c8 x10: 0000000000000000
> [   54.271630] x9 : ffff0023eac13618 x8 : 0000000040040000
> [   54.276928] x7 : 0000000000000000 x6 : ffff0023be268a90
> [   54.282226] x5 : ffff0023be74aa00 x4 : 0000000000000000
> [   54.287524] x3 : ffff8000119f0f30 x2 : dead000000000100
> [   54.292821] x1 : dead000000000122 x0 : 0000000000000000
> [   54.298119] Call trace:
> [   54.300553]  device_del+0x194/0x398
> [   54.304030]  enclosure_remove_device+0xb4/0x100
> [   54.308548]  ses_intf_remove+0x98/0xd8
> [   54.312283]  device_del+0xfc/0x398
> [   54.315671]  device_unregister+0x14/0x30
> [   54.319580]  __scsi_remove_device+0xf0/0x130
> [   54.323836]  scsi_remove_device+0x28/0x40
> [   54.327832]  scsi_remove_target+0x1bc/0x250
> [   54.332002]  sas_rphy_remove+0x5c/0x60
> [   54.335738]  sas_rphy_delete+0x14/0x28
> [   54.339473]  sas_destruct_devices+0x5c/0x98
> [   54.343642]  sas_revalidate_domain+0xa0/0x178
> [   54.347986]  process_one_work+0x1e0/0x358
> [   54.351982]  worker_thread+0x40/0x488
> [   54.355631]  kthread+0x118/0x120
> [   54.358846]  ret_from_fork+0x10/0x18
> [   54.362410] Code: 91028278 aa1903e0 9415f01f a94c0662 (f9000441)
> [   54.368489] ---[ end trace 38c672fcf89c95f7 ]---
> 
> I tested on v5.4 and no such issue, but maybe the driver core
> changes 
> have exposed a ses/enclosure issue.
> 
> Checking:
> 
> int enclosure_remove_device(struct enclosure_device *edev, struct
> device 
> *dev)
> {
> 	struct enclosure_component *cdev;
> 	int i;
> 
> 	if (!edev || !dev)
> 		return -EINVAL;
> 
> 	for (i = 0; i < edev->components; i++) {
> 		cdev = &edev->component[i];
> 		if (cdev->dev == dev) {
> 			enclosure_remove_links(cdev);
> 			device_del(&cdev->cdev);
> 			put_device(dev);
> 			cdev->dev = NULL;
> 			return device_add(&cdev->cdev);
> 		}
> 	}
> 	return -ENODEV;
> }

The design of the code is simply to remove the link to the inserted
device which has been removed.

I *think* this means the calls to device_del and device_add are
unnecessary and should go.  enclosure_remove_links and the put of the
enclosed device should be sufficient.

James