Running sosreport/slabtop causes kernel panic after drm module unload/reload

Issue

• sosreport or running slabtop (even cat /proc/slabinfo) causes kernel panic

<3>SLAB: cache with size 2096 has lost its name
<5>Bridge firewalling registered
<1>BUG: unable to handle kernel paging request at ffffffffa0e1896a
<1>IP: [<ffffffff812980e9>] strnlen+0x9/0x40
<4>PGD 1a8f067 PUD 1a93063 PMD 183804a067 PTE 0
<4>Oops: 0000 [#1] SMP 
<4>last sysfs file: /sys/module/dm_log/refcnt
<4>CPU 21 
<4>Modules linked in: bridge nvidia(P)(U) autofs4 nfs lockd fscache auth_rpcgss nfs_acl sunrpc 8021q garp stp llc ppdev parport_pc parport fuse cpufreq_ondemand acpi_cpufreq freq_table mperf ipv6 ipeak(U) regex(U) uinput sg microcode serio_raw iTCO_wdt iTCO_vendor_support igb i2c_algo_bit dcdbas ixgbe dca mdio snd_hda_codec_hdmi sb_edac edac_core snd_hda_codec_realtek i2c_i801 i2c_core snd_hda_codec_generic lpc_ich mfd_core snd_hda_intel snd_hda_codec snd_hwdep snd_seq snd_seq_device snd_pcm snd_timer snd soundcore snd_page_alloc e1000e ptp pps_core shpchp ext4 jbd2 mbcache sd_mod crc_t10dif sr_mod cdrom xhci_hcd megaraid_sas ahci wmi dm_mirror dm_region_hash dm_log dm_mod [last unloaded: drm]
<4>
<4>Pid: 12038, comm: sosreport Tainted: P           -- ------------    2.6.32-573.3.1.el6.x86_64 #1 Dell Inc. Precision T7610/0NK70N
<4>RIP: 0010:[<ffffffff812980e9>]  [<ffffffff812980e9>] strnlen+0x9/0x40
..
<4>Process sosreport (pid: 12038, threadinfo ffff883045c2c000, task ffff8830477c1520)
..
<4>Call Trace:
<4> [<ffffffff81299500>] string+0x40/0x100
<4> [<ffffffff8129af38>] vsnprintf+0x218/0x5e0
<4> [<ffffffff81156e6f>] ? vma_adjust+0x11f/0x5e0
<4> [<ffffffff811b76f2>] seq_vprintf+0x32/0x60
<4> [<ffffffff811b775d>] seq_printf+0x3d/0x40
<4> [<ffffffff81177eaa>] s_show+0x26a/0x330
<4> [<ffffffff811b7ae9>] seq_read+0x289/0x400
<4> [<ffffffff811fd39e>] proc_reg_read+0x7e/0xc0
<4> [<ffffffff81192215>] vfs_read+0xb5/0x1a0
<4> [<ffffffff81192fc6>] ? fget_light_pos+0x16/0x50
<4> [<ffffffff81192561>] sys_read+0x51/0xb0
<4> [<ffffffff810e88ae>] ? __audit_syscall_exit+0x25e/0x290
<4> [<ffffffff8100b0d2>] system_call_fastpath+0x16/0x1b

• unloading and loading drm module multiple times can cause panic

Kernel panic - not syncing: kmem_cache_create(): failed to create slab `idr2_layer_cache'

Pid: 6149, comm: modprobe Not tainted 2.6.32-573.22.1.el6.x86_64 #1
Call Trace:
 [<ffffffff81538c41>] ? panic+0xa7/0x16f
 [<ffffffff81011085>] ? show_trace+0x15/0x20
 [<ffffffff8117b750>] ? kmem_cache_create+0x520/0x5a0
 [<ffffffff8129f7e0>] ? kvasprintf+0x70/0x90
 [<ffffffffa0218000>] ? drm_core_init+0x0/0x13b [drm]
 [<ffffffffa0218000>] ? drm_core_init+0x0/0x13b [drm]
 [<ffffffffa021815a>] ? idr2_init_cache+0x1f/0x28 [drm]
 [<ffffffffa021816c>] ? drm_backport_init+0x9/0xd [drm]
 [<ffffffffa021800e>] ? drm_core_init+0xe/0x13b [drm]
 [<ffffffffa0218000>] ? drm_core_init+0x0/0x13b [drm]
 [<ffffffff810020d0>] ? do_one_initcall+0xc0/0x280
 [<ffffffff810c2f71>] ? sys_init_module+0xe1/0x250
 [<ffffffff8100b0d2>] ? system_call_fastpath+0x16/0x1b