[PATCH] udevProcessCSS: fix segfault
Boris Fiuczynski
fiuczy at linux.ibm.com
Tue Sep 22 08:45:09 UTC 2020
On 9/22/20 8:26 AM, Erik Skultety wrote:
> On Mon, Sep 21, 2020 at 07:06:32PM +0200, Marc Hartmayer wrote:
>> Don't process subchannel devices where `def->driver` is not set. This
>> fixes the following segfault:
>>
>> Thread 21 "nodedev-init" received signal SIGSEGV, Segmentation fault.
>> [Switching to Thread 0x3ffb08fc910 (LWP 64303)]
>> (gdb) bt
>> #0 0x000003fffd1272b4 in __strcmp_vx () at /lib64/libc.so.6
>> #1 0x000003ffc260c3a8 in udevProcessCSS (device=0x3ff9018d130, def=0x3ff90194a90)
>> #2 0x000003ffc260cb78 in udevGetDeviceDetails (device=0x3ff9018d130, def=0x3ff90194a90)
>> #3 0x000003ffc260d126 in udevAddOneDevice (device=0x3ff9018d130)
>> #4 0x000003ffc260d414 in udevProcessDeviceListEntry (udev=0x3ffa810d800, list_entry=0x3ff90001990)
>> #5 0x000003ffc260d638 in udevEnumerateDevices (udev=0x3ffa810d800)
>> #6 0x000003ffc260e08e in nodeStateInitializeEnumerate (opaque=0x3ffa810d800)
>> #7 0x000003fffdaa14b6 in virThreadHelper (data=0x3ffa810df00)
>> #8 0x000003fffc309ed6 in start_thread ()
>> #9 0x000003fffd185e66 in thread_start ()
>> (gdb) p *def
>> $2 = {
>> name = 0x0,
>> sysfs_path = 0x3ff90198e80 "/sys/devices/css0/0.0.ff40",
>
> Okay, this patch fixes the segfault. However, if ^this generated it because the
> driver name is not set, how do we even get to the resulting device tree as
> outlined in 05e6cdafa6e0?
>
> +- css_0_0_003a
> |
> +- ccw_0_0_1a2b
> |
> +- scsi_host0
>
> What kind of CSS device is the one causing the error? If we skip this CSS
> device, we don't generate a name for it and don't put it in the list, so I'm
> quite puzzled on what I missed in the IBM document and thus in the review
> process.
>
> FWIW:
> Reviewed-by: Erik Skultety <eskultet at redhat.com>
>
Erik,
for whatever reason Marcs system does not have the subchannel device
driver "chsc_subchannel" loaded. Therefore the subchannel is not bound
to any driver and by the way this would be a filtered device since we
want to show the users only io_subchannel and vfio_ccw subchannels.
The tree above shows a subchannel bound to the io_subchannel device driver.
Maybe it helps you to see a full example of how it looks on my system:
# virsh nodedev-list --tree
computer
|
+- css_0_0_000e
| |
| +- ccw_0_0_f500
|
+- css_0_0_000f
| |
| +- ccw_0_0_f501
|
+- css_0_0_0010
| |
| +- ccw_0_0_f502
|
+- css_0_0_0011
| |
| +- ccw_0_0_bd00
|
+- css_0_0_0012
| |
| +- ccw_0_0_bd01
|
+- css_0_0_0013
| |
| +- ccw_0_0_bd02
|
+- css_0_0_002f
| |
| +- ccw_0_0_19c0
| |
| +- scsi_host3
| |
| +- scsi_target3_0_1
| |
| +- scsi_3_0_1_1078935649
| |
| +- block_sda_36005076307ffc5e3000000000000614f
| +- scsi_generic_sg0
|
+- css_0_0_0038
| |
| +- ccw_0_0_1900
| |
| +- scsi_host1
| |
| +- scsi_target1_0_0
| | |
| | +- scsi_1_0_0_1075986530
| | | |
| | | +- block_sdd_36005076307ffc5e30000000000006222
| | | +- scsi_generic_sg3
| | |
| | +- scsi_1_0_0_1078935649
| | |
| | +- block_sdc_36005076307ffc5e3000000000000614f
| | +- scsi_generic_sg2
| |
| +- scsi_target1_0_2
| |
| +- scsi_1_0_2_1075986530
| | |
| | +- block_sdf_36005076307ffc5e30000000000006222
| | +- scsi_generic_sg5
| |
| +- scsi_1_0_2_1078935649
| |
| +- block_sde_36005076307ffc5e3000000000000614f
| +- scsi_generic_sg4
|
+- css_0_0_003a
| |
| +- ccw_0_0_1940
| |
| +- scsi_host0
| |
| +- scsi_target0_0_1
| | |
| | +- scsi_0_0_1_1075986530
| | | |
| | | +- block_sdi_36005076307ffc5e30000000000006222
| | | +- scsi_generic_sg8
| | |
| | +- scsi_0_0_1_1078935649
| | |
| | +- block_sdh_36005076307ffc5e3000000000000614f
| | +- scsi_generic_sg7
| |
| +- scsi_target0_0_3
| |
| +- scsi_0_0_3_1075986530
| | |
| | +- block_sdg_36005076307ffc5e30000000000006222
| | +- scsi_generic_sg6
| |
| +- scsi_0_0_3_1078935649
| |
| +- block_sdb_36005076307ffc5e3000000000000614f
| +- scsi_generic_sg1
|
+- css_0_0_003c
| |
| +- ccw_0_0_1980
| |
| +- scsi_host2
|
+- css_0_0_006b
| |
| +- ccw_0_0_1000
| |
| +- block_dasdg_IBM_750000000DHVL1_0001_00
|
+- css_0_0_006c
| |
| +- ccw_0_0_1001
| |
| +- block_dasda_IBM_750000000DHVL1_0001_01
|
+- css_0_0_006d
| |
| +- ccw_0_0_1002
| |
| +- block_dasdb_IBM_750000000DHVL1_0001_02
|
+- css_0_0_006e
| |
| +- ccw_0_0_1003
| |
| +- block_dasdc_IBM_750000000DHVL1_0001_03
|
+- css_0_0_006f
| |
| +- ccw_0_0_1004
| |
| +- block_dasdd_IBM_750000000DHVL1_0001_04
|
+- css_0_0_0070
| |
| +- ccw_0_0_1005
| |
| +- block_dasdh_IBM_750000000DHVL1_0001_05
|
+- css_0_0_0071
| |
| +- ccw_0_0_1006
| |
| +- block_dasdf_IBM_750000000DHVL1_0001_06
|
+- css_0_0_0072
| |
| +- mdev_2e7237a7_0445_407e_b880_96f63a3cd17d
|
+- net_encbd00_02_ff_e3_80_c4_ef
+- net_encf500_02_ff_e3_80_76_89
+- net_lo_00_00_00_00_00_00
+- pci_0001_00_00_0
|
+- net_enP1s8_82_01_2d_0c_bb_b0
+- net_enP1s8d1_82_01_2d_0c_bb_b1
All subchannels but css_0_0_0072 are bound to io_subchannel.
css_0_0_0072 is bound to vfio-ccw and therefore lists an mdev as child.
Here are the xml dumps:
# virsh nodedev-dumpxml css_0_0_0071
<device>
<name>css_0_0_0071</name>
<path>/sys/devices/css0/0.0.0071</path>
<parent>computer</parent>
<driver>
<name>io_subchannel</name>
</driver>
<capability type='css'>
<cssid>0x0</cssid>
<ssid>0x0</ssid>
<devno>0x0071</devno>
</capability>
</device>
# virsh nodedev-dumpxml css_0_0_0072
<device>
<name>css_0_0_0072</name>
<path>/sys/devices/css0/0.0.0072</path>
<parent>computer</parent>
<driver>
<name>vfio_ccw</name>
</driver>
<capability type='css'>
<cssid>0x0</cssid>
<ssid>0x0</ssid>
<devno>0x0072</devno>
</capability>
</device>
I hope that helps a bit...
--
Mit freundlichen Grüßen/Kind regards
Boris Fiuczynski
IBM Deutschland Research & Development GmbH
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