Hi,
My kernel crashes every time X starts (for the past week). It started happening with the nvidia 3.90 drivers that were compiled with gcc 8.
nvidia-bug-report.log.gz: https://ufile.io/q7fg4
This is what dmesg gives me:
[ 229.521617] ------------[ cut here ]------------
[ 229.521620] Bad or missing usercopy whitelist? Kernel memory overwrite attempt detected to SLUB object 'nvidia_stack_cache' (offset 12204, size 4)!
[ 229.521629] WARNING: CPU: 3 PID: 1716 at mm/usercopy.c:81 usercopy_warn+0x7d/0xa0
[ 229.521630] Modules linked in: rfcomm fuse vhost_net vhost tap xt_CHECKSUM iptable_mangle ipt_MASQUERADE nf_nat_masquerade_ipv4 iptable_nat nf_nat_ipv4 nf_nat nf_conntrack_ipv4 nf_defrag_ipv4 xt_conntrack nf_conntrack libcrc32c ipt_REJECT nf_reject_ipv4 xt_tcpudp tun bridge stp llc devlink ebtable_filter ebtables ip6table_filter ip6_tables iptable_filter bnep nct6775 hwmon_vid snd_hda_codec_hdmi nvidia_drm(PO) nls_iso8859_1 nvidia_modeset(PO) eeepc_wmi snd_hda_codec_realtek nls_cp437 asus_wmi snd_hda_codec_generic iTCO_wdt iTCO_vendor_support wmi_bmof sparse_keymap vfat mxm_wmi wl(PO) fat nvidia(PO) intel_rapl x86_pkg_temp_thermal intel_powerclamp coretemp btusb kvm_intel btrtl cfg80211 btbcm kvm btintel drm_kms_helper bluetooth drm snd_hda_intel intel_cstate snd_hda_codec intel_uncore intel_rapl_perf
[ 229.521655] snd_hda_core agpgart ipmi_devintf snd_hwdep ipmi_msghandler snd_pcm pcspkr syscopyarea sysfillrect ecdh_generic sysimgblt e1000e fb_sys_fops snd_timer rfkill i2c_i801 snd mei_me ptp mousedev input_leds led_class joydev lpc_ich soundcore mei shpchp pps_core rtc_cmos wmi evdev mac_hid i2c_dev sg crypto_user ip_tables x_tables algif_skcipher af_alg uas usb_storage hid_generic usbhid hid sr_mod cdrom sd_mod crct10dif_pclmul crc32_pclmul ghash_clmulni_intel pcbc ahci libahci aesni_intel xhci_pci libata crypto_simd glue_helper ehci_pci cryptd xhci_hcd ehci_hcd scsi_mod usbcore usb_common aes_x86_64 ext4 crc32c_generic crc32c_intel crc16 mbcache jbd2 fscrypto dm_crypt dm_mod vfio_pci irqbypass vfio_virqfd vfio_iommu_type1 vfio
[ 229.521688] CPU: 3 PID: 1716 Comm: Xorg Tainted: P O 4.16.7-1-ARCH #1
[ 229.521689] Hardware name: System manufacturer System Product Name/RAMPAGE IV BLACK EDITION, BIOS 0801 07/04/2014
[ 229.521690] RIP: 0010:usercopy_warn+0x7d/0xa0
[ 229.521691] RSP: 0018:ffffae214715fcb0 EFLAGS: 00010282
[ 229.521692] RAX: 0000000000000000 RBX: 0000000000000004 RCX: 0000000000000001
[ 229.521692] RDX: 0000000080000001 RSI: ffffffffbde7071c RDI: 00000000ffffffff
[ 229.521693] RBP: 0000000000000000 R08: 0000000000000098 R09: 0000000000000590
[ 229.521694] R10: 0000000000000000 R11: 0000000000000001 R12: ffffa1847aecdfb0
[ 229.521694] R13: ffffa1847aecdfac R14: ffffa18480ca9800 R15: ffffa18480ca9800
[ 229.521695] FS: 00007fb3264c3940(0000) GS:ffffa1874fcc0000(0000) knlGS:0000000000000000
[ 229.521696] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 229.521697] CR2: 00007fb31e509f70 CR3: 00000004592b4005 CR4: 00000000001626e0
[ 229.521697] Call Trace:
[ 229.521701] __check_object_size+0xf0/0x180
[ 229.521827] ? os_memcpy_from_user+0x1b/0x40 [nvidia]
[ 229.521936] ? _nv001114rm+0x7df/0x850 [nvidia]
[ 229.522050] ? rm_ioctl+0x73/0x100 [nvidia]
[ 229.522054] ? __kmalloc+0xf0/0x220
[ 229.522118] ? nvidia_ioctl+0x532/0x710 [nvidia]
[ 229.522192] ? nvidia_frontend_unlocked_ioctl+0x3a/0x50 [nvidia]
[ 229.522194] ? do_vfs_ioctl+0xa4/0x610
[ 229.522196] ? __fput+0x124/0x1e0
[ 229.522198] ? preempt_count_add+0x68/0xa0
[ 229.522200] ? SyS_ioctl+0x74/0x80
[ 229.522202] ? do_syscall_64+0x74/0x190
[ 229.522204] ? entry_SYSCALL_64_after_hwframe+0x3d/0xa2
[ 229.522206] Code: a9 e7 bd 41 51 4d 89 d8 48 c7 c0 39 a8 e6 bd 49 89 f1 48 89 f9 48 0f 45 c2 48 c7 c7 38 aa e7 bd 4c 89 d2 48 89 c6 e8 0d d7 e3 ff <0f> 0b 48 83 c4 18 c3 48 c7 c6 1c 07 e7 bd 49 89 f1 49 89 f3 eb
[ 229.522226] ---[ end trace 5fe876c61ea774f4 ]---
nvidia-bug-report.log.gz (84.3 KB)
https://devtalk.nvidia.com/default/topic/1031067/linux/-linux416-nvidia-390-48-nvidia_stack_cache-rip-0010-usercopy_warn-0x7e-0xa0/
After trying the option on this form:
slab_common.usercopy_fallback=Y
The bug reporter hangs and outputs this now https://ufile.io/w4f1d
Now I get stuff like this:
[ 245.387083] INFO: task Xorg:827 blocked for more than 120 seconds.
[ 245.387086] Tainted: P O 4.16.7-1-ARCH #1
[ 245.387088] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 245.387091] Xorg D 0 827 757 0x00400000
[ 245.387094] Call Trace:
[ 245.387099] ? __schedule+0x282/0x890
[ 245.387106] schedule+0x32/0x90
[ 245.387110] schedule_timeout+0x311/0x4a0
[ 245.387115] ? enqueue_task_fair+0x99/0x6f0
[ 245.387120] ? native_sched_clock+0x5d/0x90
[ 245.387123] ? resched_curr+0x23/0xd0
[ 245.387128] __down+0x7d/0xd0
[ 245.387133] down+0x3b/0x50
[ 245.387317] os_acquire_mutex+0x30/0x40 [nvidia]
[ 245.387641] _nv031508rm+0x5c/0x120 [nvidia]
[ 245.387966] ? _nv008486rm+0x218/0x2b0 [nvidia]
[ 245.388289] ? _nv001019rm+0xe/0x20 [nvidia]
[ 245.388614] ? _nv007522rm+0xd8/0x100 [nvidia]
[ 245.388925] ? _nv001114rm+0x637/0x850 [nvidia]
[ 245.389236] ? rm_ioctl+0x73/0x100 [nvidia]
[ 245.389242] ? __kmalloc+0xf1/0x220
[ 245.389426] ? nvidia_ioctl+0x532/0x710 [nvidia]
[ 245.389608] ? nvidia_frontend_unlocked_ioctl+0x3a/0x50 [nvidia]
[ 245.389629] ? do_vfs_ioctl+0xa4/0x610
[ 245.389633] ? _raw_spin_unlock+0x16/0x30
[ 245.389636] ? do_fcntl+0x554/0x640
[ 245.389640] ? kmem_cache_free+0x1d4/0x200
[ 245.389645] ? SyS_ioctl+0x74/0x80
[ 245.389649] ? do_syscall_64+0x74/0x190
[ 245.389652] ? entry_SYSCALL_64_after_hwframe+0x3d/0xa2
[ 368.261040] INFO: task kworker/5:1:91 blocked for more than 120 seconds.
[ 368.261044] Tainted: P O 4.16.7-1-ARCH #1
[ 368.261045] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 368.261046] kworker/5:1 D 0 91 2 0x80000000
[ 368.261181] Workqueue: events os_execute_work_item [nvidia]
[ 368.261182] Call Trace:
[ 368.261189] ? __schedule+0x282/0x890
[ 368.261191] schedule+0x32/0x90
[ 368.261193] schedule_timeout+0x311/0x4a0
[ 368.261194] ? schedule+0x3c/0x90
[ 368.261195] ? schedule_timeout+0x311/0x4a0
[ 368.261197] __down+0x7d/0xd0
[ 368.261198] ? acpi_idle_do_entry+0x20/0x40
[ 368.261202] down+0x3b/0x50
[ 368.261267] os_acquire_mutex+0x30/0x40 [nvidia]
[ 368.261381] _nv008497rm+0x307/0x3c0 [nvidia]
[ 368.261496] ? _nv031539rm+0x7e/0xb0 [nvidia]
[ 368.261644] ? _nv007749rm+0x6f/0x180 [nvidia]
[ 368.261753] ? _nv001065rm+0x84/0xe0 [nvidia]
[ 368.261861] ? rm_execute_work_item+0x49/0xc0 [nvidia]
[ 368.261864] ? sysfs_slab_alias+0x61/0x80
[ 368.261929] ? os_execute_work_item+0x40/0x60 [nvidia]
[ 368.261931] ? process_one_work+0x1d1/0x3b0
[ 368.261933] ? worker_thread+0x2b/0x3d0
[ 368.261934] ? process_one_work+0x3b0/0x3b0
[ 368.261935] ? kthread+0x112/0x130
[ 368.261936] ? kthread_create_on_node+0x60/0x60
[ 368.261938] ? ret_from_fork+0x35/0x40
[ 368.261950] INFO: task nvidia-persiste:709 blocked for more than 120 seconds.
[ 368.261952] Tainted: P O 4.16.7-1-ARCH #1
[ 368.261952] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 368.261953] nvidia-persiste D 0 709 1 0x00000004
[ 368.261954] Call Trace:
[ 368.261956] ? __schedule+0x282/0x890
[ 368.261958] schedule+0x32/0x90
[ 368.261959] schedule_timeout+0x311/0x4a0
[ 368.261961] ? _raw_spin_unlock_irqrestore+0x20/0x40
[ 368.261962] ? try_to_wake_up+0x222/0x460
[ 368.261964] __down+0x7d/0xd0
[ 368.261966] ? preempt_count_add+0x68/0xa0
[ 368.261967] down+0x3b/0x50
[ 368.262032] os_acquire_mutex+0x30/0x40 [nvidia]
[ 368.262146] _nv031508rm+0x5c/0x120 [nvidia]
[ 368.262260] ? _nv007532rm+0x129/0x1b0 [nvidia]
[ 368.262369] ? rm_kernel_rmapi_op+0x11e/0x150 [nvidia]
[ 368.262380] ? nvkms_call_rm+0x4b/0x80 [nvidia_modeset]
[ 368.262388] ? _nv002311kms+0x47/0x60 [nvidia_modeset]
[ 368.262396] ? _nv000233kms+0x87/0x350 [nvidia_modeset]
[ 368.262404] ? _nv000004kms+0x231/0x420 [nvidia_modeset]
[ 368.262410] ? nvkms_call_rm+0x5b/0x80 [nvidia_modeset]
[ 368.262418] ? _nv002282kms+0xf4/0x130 [nvidia_modeset]
[ 368.262425] ? _nv001956kms+0x525/0x5f0 [nvidia_modeset]
[ 368.262431] ? _nv001958kms+0x131/0x160 [nvidia_modeset]
[ 368.262437] ? nvkms_alloc+0x1f/0x50 [nvidia_modeset]
[ 368.262442] ? _nv000003kms+0x275/0x2a0 [nvidia_modeset]
[ 368.262444] ? __check_object_size+0xfb/0x180
[ 368.262450] ? nvKmsIoctl+0x117/0x230 [nvidia_modeset]
[ 368.262455] ? _nv001962kms+0x3d0/0x3d0 [nvidia_modeset]
[ 368.262456] ? preempt_count_add+0x68/0xa0
[ 368.262458] ? _raw_spin_lock_irqsave+0x25/0x50
[ 368.262463] ? nvkms_ioctl_common+0x3b/0x80 [nvidia_modeset]
[ 368.262469] ? nvkms_ioctl+0x67/0xa0 [nvidia_modeset]
[ 368.262532] ? nvidia_frontend_unlocked_ioctl+0x3a/0x50 [nvidia]
[ 368.262534] ? do_vfs_ioctl+0xa4/0x610
[ 368.262536] ? __do_page_fault+0x237/0x570
[ 368.262538] ? SyS_ioctl+0x74/0x80
[ 368.262540] ? do_syscall_64+0x74/0x190
[ 368.262541] ? entry_SYSCALL_64_after_hwframe+0x3d/0xa2
[ 368.262549] INFO: task Xorg:827 blocked for more than 120 seconds.
[ 368.262551] Tainted: P O 4.16.7-1-ARCH #1
[ 368.262551] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 368.262552] Xorg D 0 827 757 0x00400000
[ 368.262553] Call Trace:
[ 368.262555] ? __schedule+0x282/0x890
[ 368.262557] schedule+0x32/0x90
[ 368.262558] schedule_timeout+0x311/0x4a0
[ 368.262560] ? enqueue_task_fair+0x99/0x6f0
[ 368.262563] ? native_sched_clock+0x5d/0x90
[ 368.262564] ? resched_curr+0x23/0xd0
[ 368.262566] __down+0x7d/0xd0
[ 368.262568] down+0x3b/0x50
[ 368.262632] os_acquire_mutex+0x30/0x40 [nvidia]
[ 368.262746] _nv031508rm+0x5c/0x120 [nvidia]
[ 368.262860] ? _nv008486rm+0x218/0x2b0 [nvidia]
[ 368.262973] ? _nv001019rm+0xe/0x20 [nvidia]
[ 368.263087] ? _nv007522rm+0xd8/0x100 [nvidia]
[ 368.263196] ? _nv001114rm+0x637/0x850 [nvidia]
[ 368.263305] ? rm_ioctl+0x73/0x100 [nvidia]
[ 368.263307] ? __kmalloc+0xf1/0x220
[ 368.263371] ? nvidia_ioctl+0x532/0x710 [nvidia]
[ 368.263435] ? nvidia_frontend_unlocked_ioctl+0x3a/0x50 [nvidia]
[ 368.263437] ? do_vfs_ioctl+0xa4/0x610
[ 368.263438] ? _raw_spin_unlock+0x16/0x30
[ 368.263439] ? do_fcntl+0x554/0x640
[ 368.263440] ? kmem_cache_free+0x1d4/0x200
[ 368.263442] ? SyS_ioctl+0x74/0x80
[ 368.263443] ? do_syscall_64+0x74/0x190
[ 368.263445] ? entry_SYSCALL_64_after_hwframe+0x3d/0xa2
[ 491.137899] INFO: task kworker/5:1:91 blocked for more than 120 seconds.
[ 491.137905] Tainted: P O 4.16.7-1-ARCH #1
[ 491.137906] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 491.137908] kworker/5:1 D 0 91 2 0x80000000
[ 491.138073] Workqueue: events os_execute_work_item [nvidia]
[ 491.138074] Call Trace:
[ 491.138083] ? __schedule+0x282/0x890
[ 491.138086] schedule+0x32/0x90
[ 491.138089] schedule_timeout+0x311/0x4a0
[ 491.138091] ? schedule+0x3c/0x90
[ 491.138093] ? schedule_timeout+0x311/0x4a0
[ 491.138096] __down+0x7d/0xd0
[ 491.138098] ? acpi_idle_do_entry+0x20/0x40
[ 491.138102] down+0x3b/0x50
[ 491.138203] os_acquire_mutex+0x30/0x40 [nvidia]
[ 491.138379] _nv008497rm+0x307/0x3c0 [nvidia]
[ 491.138555] ? _nv031539rm+0x7e/0xb0 [nvidia]
[ 491.138784] ? _nv007749rm+0x6f/0x180 [nvidia]
[ 491.138952] ? _nv001065rm+0x84/0xe0 [nvidia]
[ 491.139120] ? rm_execute_work_item+0x49/0xc0 [nvidia]
[ 491.139123] ? sysfs_slab_alias+0x61/0x80
[ 491.139224] ? os_execute_work_item+0x40/0x60 [nvidia]
[ 491.139227] ? process_one_work+0x1d1/0x3b0
[ 491.139229] ? worker_thread+0x2b/0x3d0
[ 491.139231] ? process_one_work+0x3b0/0x3b0
[ 491.139233] ? kthread+0x112/0x130
[ 491.139234] ? kthread_create_on_node+0x60/0x60
[ 491.139236] ? ret_from_fork+0x35/0x40
[ 491.139252] INFO: task nvidia-persiste:709 blocked for more than 120 seconds.
[ 491.139254] Tainted: P O 4.16.7-1-ARCH #1
[ 491.139255] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 491.139256] nvidia-persiste D 0 709 1 0x00000004
[ 491.139258] Call Trace:
[ 491.139261] ? __schedule+0x282/0x890
[ 491.139264] schedule+0x32/0x90
[ 491.139266] schedule_timeout+0x311/0x4a0
[ 491.139268] ? _raw_spin_unlock_irqrestore+0x20/0x40
[ 491.139270] ? try_to_wake_up+0x222/0x460
[ 491.139273] __down+0x7d/0xd0
[ 491.139275] ? preempt_count_add+0x68/0xa0
[ 491.139277] down+0x3b/0x50
[ 491.139378] os_acquire_mutex+0x30/0x40 [nvidia]
[ 491.139553] _nv031508rm+0x5c/0x120 [nvidia]
[ 491.139738] ? _nv007532rm+0x129/0x1b0 [nvidia]
[ 491.139905] ? rm_kernel_rmapi_op+0x11e/0x150 [nvidia]
[ 491.139919] ? nvkms_call_rm+0x4b/0x80 [nvidia_modeset]
[ 491.139932] ? _nv002311kms+0x47/0x60 [nvidia_modeset]
[ 491.139945] ? _nv000233kms+0x87/0x350 [nvidia_modeset]
[ 491.139957] ? _nv000004kms+0x231/0x420 [nvidia_modeset]
[ 491.139966] ? nvkms_call_rm+0x5b/0x80 [nvidia_modeset]
[ 491.139979] ? _nv002282kms+0xf4/0x130 [nvidia_modeset]
[ 491.139989] ? _nv001956kms+0x525/0x5f0 [nvidia_modeset]
[ 491.139999] ? _nv001958kms+0x131/0x160 [nvidia_modeset]
[ 491.140007] ? nvkms_alloc+0x1f/0x50 [nvidia_modeset]
[ 491.140016] ? _nv000003kms+0x275/0x2a0 [nvidia_modeset]
[ 491.140019] ? __check_object_size+0xfb/0x180
[ 491.140028] ? nvKmsIoctl+0x117/0x230 [nvidia_modeset]
[ 491.140037] ? _nv001962kms+0x3d0/0x3d0 [nvidia_modeset]
[ 491.140038] ? preempt_count_add+0x68/0xa0
[ 491.140040] ? _raw_spin_lock_irqsave+0x25/0x50
[ 491.140049] ? nvkms_ioctl_common+0x3b/0x80 [nvidia_modeset]
[ 491.140057] ? nvkms_ioctl+0x67/0xa0 [nvidia_modeset]
[ 491.140155] ? nvidia_frontend_unlocked_ioctl+0x3a/0x50 [nvidia]
[ 491.140158] ? do_vfs_ioctl+0xa4/0x610
[ 491.140160] ? __do_page_fault+0x237/0x570
[ 491.140163] ? SyS_ioctl+0x74/0x80
[ 491.140166] ? do_syscall_64+0x74/0x190
[ 491.140168] ? entry_SYSCALL_64_after_hwframe+0x3d/0xa2
[ 491.140179] INFO: task Xorg:827 blocked for more than 120 seconds.
[ 491.140181] Tainted: P O 4.16.7-1-ARCH #1
[ 491.140182] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 491.140183] Xorg D 0 827 757 0x00400000
[ 491.140185] Call Trace:
[ 491.140188] ? __schedule+0x282/0x890
[ 491.140191] schedule+0x32/0x90
[ 491.140193] schedule_timeout+0x311/0x4a0
[ 491.140196] ? enqueue_task_fair+0x99/0x6f0
[ 491.140199] ? native_sched_clock+0x5d/0x90
[ 491.140201] ? resched_curr+0x23/0xd0
[ 491.140204] __down+0x7d/0xd0
[ 491.140206] down+0x3b/0x50
[ 491.140307] os_acquire_mutex+0x30/0x40 [nvidia]
[ 491.140482] _nv031508rm+0x5c/0x120 [nvidia]
[ 491.140657] ? _nv008486rm+0x218/0x2b0 [nvidia]
[ 491.140832] ? _nv001019rm+0xe/0x20 [nvidia]
[ 491.141008] ? _nv007522rm+0xd8/0x100 [nvidia]
[ 491.141176] ? _nv001114rm+0x637/0x850 [nvidia]
[ 491.141344] ? rm_ioctl+0x73/0x100 [nvidia]
[ 491.141359] ? __kmalloc+0xf1/0x220
[ 491.141459] ? nvidia_ioctl+0x532/0x710 [nvidia]
[ 491.141557] ? nvidia_frontend_unlocked_ioctl+0x3a/0x50 [nvidia]
[ 491.141562] ? do_vfs_ioctl+0xa4/0x610
[ 491.141564] ? _raw_spin_unlock+0x16/0x30
[ 491.141566] ? do_fcntl+0x554/0x640
[ 491.141567] ? kmem_cache_free+0x1d4/0x200
[ 491.141570] ? SyS_ioctl+0x74/0x80
[ 491.141572] ? do_syscall_64+0x74/0x190
[ 491.141574] ? entry_SYSCALL_64_after_hwframe+0x3d/0xa2
[ 614.016281] INFO: task kworker/5:1:91 blocked for more than 120 seconds.
[ 614.016303] Tainted: P O 4.16.7-1-ARCH #1
[ 614.016306] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 614.016310] kworker/5:1 D 0 91 2 0x80000000
[ 614.016562] Workqueue: events os_execute_work_item [nvidia]
[ 614.016565] Call Trace:
[ 614.016578] ? __schedule+0x282/0x890
[ 614.016585] schedule+0x32/0x90
[ 614.016590] schedule_timeout+0x311/0x4a0
[ 614.016594] ? schedule+0x3c/0x90
[ 614.016598] ? schedule_timeout+0x311/0x4a0
[ 614.016604] __down+0x7d/0xd0
[ 614.016607] ? acpi_idle_do_entry+0x20/0x40
[ 614.016614] down+0x3b/0x50
[ 614.016816] os_acquire_mutex+0x30/0x40 [nvidia]
[ 614.017168] _nv008497rm+0x307/0x3c0 [nvidia]
[ 614.017521] ? _nv031539rm+0x7e/0xb0 [nvidia]
[ 614.017993] ? _nv007749rm+0x6f/0x180 [nvidia]
[ 614.018355] ? _nv001065rm+0x84/0xe0 [nvidia]
[ 614.018694] ? rm_execute_work_item+0x49/0xc0 [nvidia]
[ 614.018701] ? sysfs_slab_alias+0x61/0x80
[ 614.018902] ? os_execute_work_item+0x40/0x60 [nvidia]
[ 614.018907] ? process_one_work+0x1d1/0x3b0
[ 614.018912] ? worker_thread+0x2b/0x3d0
[ 614.018916] ? process_one_work+0x3b0/0x3b0
[ 614.018919] ? kthread+0x112/0x130
[ 614.018922] ? kthread_create_on_node+0x60/0x60
[ 614.018927] ? ret_from_fork+0x35/0x40
nvidia-bug-report.log.gz (66.5 KB)