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List:       linux-scsi
Subject:    [REGRESSION v4.3] scsi_dh: use-after-free when removing scsi device
From:       Junichi Nomura <j-nomura () ce ! jp ! nec ! com>
Date:       2015-09-30 0:35:50
Message-ID: 20150930003549.GA4857 () xzibit ! linux ! bs1 ! fc ! nec ! co ! jp
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With v4.3-rc3, stress testing of SCSI device addition/removal quickly
trigger random crash in memory allocator (e.g. __kmalloc).  I found that
a commit 086b91d052eb ("scsi_dh: integrate into the core SCSI code")
moved the call of scsi_dh->detach() to very early part of sdev tear down
process (scsi_remove_device()). As a result, related data structure such
as alua_dh_data can be freed while rtpg/stpg are still in-flight.

Here is an example of crash log.  You can see strange rtpg log
'port group 25a43100' for 514:0:0:0 after 'Detached':

> > [  170.518427] sd 517:0:0:0: [sdd] Attached SCSI disk
> > [  170.528681] sd 514:0:0:0: alua: Detached
> > [  170.528720] sd 517:0:0:0: alua: Detached
> > [  170.528827] sd 515:0:0:0: alua: Detached
> > [  170.528922] sd 514:0:0:0: alua: port group 25a43100 state A non-preferred \
> > supports tolusna [  170.528924] device-mapper: multipath: Failing path 8:16.
> > [  170.529059] device-mapper: table: 253:0: multipath: error getting device
> > [  170.529060] device-mapper: ioctl: error adding target to table
> > [  170.529212] device-mapper: multipath: Failing path 8:0.
> > [  170.540498] sd 516:0:0:0: alua: Detached
> > [  170.540543] sd 515:0:0:0: [sdb] Synchronizing SCSI cache
> > [  170.541849] sd 517:0:0:0: [sdd] Synchronizing SCSI cache
> > [  170.542393] sd 514:0:0:0: [sda] Synchronizing SCSI cache
> > [  170.546836] BUG: unable to handle kernel paging request at 0000001028000000
> > [  170.548499] IP: [<ffffffff811dce0a>] kmem_cache_alloc_trace+0x7a/0x1f0
> > [  170.550069] sd 516:0:0:0: [sdc] Synchronizing SCSI cache
> > [  170.551540] PGD 0 
> > [  170.552686] Oops: 0000 [#1] SMP 
> > [  170.553946] Modules linked in: dm_queue_length sd_mod iscsi_tcp libiscsi_tcp \
> > libiscsi scsi_transport_iscsi nls_utf8 isofs cirrus ttm drm_kms_helper \
> > syscopyarea crct10dif_pclmul sysfillrect crc32_pclmul sys imgblt \
> > ghash_clmulni_intel fb_sys_fops aesni_intel drm lrw gf128mul virtio_console \
> > glue_helper ablk_helper ppdev cryptd parport_pc i2c_piix4 serio_raw pcspkr \
> > parport i2c_core virtio_balloon acpi_cpufreq xfs l ibcrc32c sr_mod cdrom \
> > ata_generic pata_acpi virtio_blk virtio_net crc32c_intel floppy ata_piix \
> > virtio_pci libata virtio_ring virtio sunrpc dm_mirror dm_region_hash dm_log \
> > dm_multipath dm_mod [  170.564500] CPU: 2 PID: 2255 Comm: systemd-udevd Not \
> > tainted 4.3.0-rc3 #1 [  170.566078] Hardware name: 
> > [  170.567655] task: ffff88002c729580 ti: ffff8802212e8000 task.ti: \
> > ffff8802212e8000 [  170.569320] RIP: 0010:[<ffffffff811dce0a>]  \
> > [<ffffffff811dce0a>] kmem_cache_alloc_trace+0x7a/0x1f0 [  170.571208] RSP: \
> > 0018:ffff8802212ebe40  EFLAGS: 00010282 [  170.572715] RAX: 0000000000000000 RBX: \
> > 00000000000080d0 RCX: 0000000000017622
> > [  170.574461] RDX: 0000000000017621 RSI: 00000000000080d0 RDI:
> > ffff880237001800
> > [  170.576148] RBP: ffff8802212ebe78 R08: 000000000001a160 R09:
> > ffff8800afda5460
> > [  170.577902] R10: ffffffff81206740 R11: 0000000000000202 R12:
> > 00000000000080d0
> > [  170.579530] R13: ffff880237001800 R14: 0000001028000000 R15:
> > ffff880237001800
> > [  170.581276] FS:  00007fd7236ae880(0000) GS:ffff88023fd00000(0000)
> > knlGS:0000000000000000
> > [  170.583110] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > [  170.584596] CR2: 0000001028000000 CR3: 0000000225199000 CR4:
> > 00000000001406e0
> > [  170.586320] Stack:
> > [  170.587495]  ffffffff81206740 0000000000000088 ffff8800bb1cec60
> > ffff8802212ebf28
> > [  170.589280]  0000000000000800 ffff8802212ebf20 0000558c20687b50
> > ffff8802212ebe90
> > [  170.591131]  ffffffff81206740 ffff8800bb1cec60 ffff8802212ebed8
> > ffffffff81206c56
> > [  170.592929] Call Trace:
> > [  170.594228]  [<ffffffff81206740>] ? alloc_pipe_info+0x20/0xb0
> > [  170.595895]  [<ffffffff81206740>] alloc_pipe_info+0x20/0xb0
> > [  170.597637]  [<ffffffff81206c56>] create_pipe_files+0x56/0x230
> > [  170.599337]  [<ffffffff8112408f>] ? __audit_syscall_entry+0xaf/0x100
> > [  170.601071]  [<ffffffff81206e64>] __do_pipe_flags+0x34/0xe0
> > [  170.602688]  [<ffffffff81206faf>] SyS_pipe2+0x2f/0xb0
> > [  170.604215]  [<ffffffff816859ae>] entry_SYSCALL_64_fastpath+0x12/0x71
> > [  170.605863] Code: 4c 03 05 2a d3 e2 7e 4d 8b 30 49 8b 40 10 4d 85 f6 0f 84 22 \
> > 01 00 00 48 85 c0 0f 84 19 01 00 00 49 63 47 20 48 8d 4a 01 4d 8b 07 <49> 8b 1c \
> > 06 4c 89 f0 65 49 0f c7 08 0f 94 c0 84 c0 74 b9 49 63  [  170.610895] RIP  \
> > [<ffffffff811dce0a>] kmem_cache_alloc_trace+0x7a/0x1f0 [  170.612728]  RSP \
> > <ffff8802212ebe40> [  170.614244] CR2: 0000001028000000
> > [  170.615745] ---[ end trace 02faa1e1a864f6bd ]---
> > [  170.617351] Kernel panic - not syncing: Fatal exception
> > [  170.619462] Kernel Offset: disabled
> > [  170.620946] ---[ end Kernel panic - not syncing: Fatal exception


Attached below is a sample reproducer for ALUA capable storage.

--- cut here --
#!/bin/bash

# Set appropriate values for your storage
hostno=2
host=host${hostno}
dev=${hostno}:0:0:0

service multipathd stop
multipath -F

n=1
while true; do
	echo "== loop $n ==" > /dev/kmsg

	echo "-- scan $host --" > /dev/kmsg
	echo '- - -' > /sys/class/scsi_host/${host}/scan

	echo "-- activate $dev --" > /dev/kmsg
	echo activate > /sys/class/scsi_device/${dev}/device/dh_state &

	echo "-- delete $dev --" > /dev/kmsg
	echo 1 > /sys/class/scsi_device/${dev}/device/delete

	n=$((n + 1))
done
--- cut here --

# lsscsi
[0:0:0:0]    cd/dvd  QEMU     QEMU DVD-ROM     1.5.  /dev/sr0 
[2:0:0:0]    disk    LIO-ORG  VirtioDisk       4.0   /dev/sda 
# ./a.sh

<system crash>

-- 
Jun'ichi Nomura, NEC Corporation--
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