Extracting prog: 4m9.037358724s
Minimizing prog: 6m13.267166033s
Simplifying prog options: 0s
Extracting C: 44.804442714s
Simplifying C: 23m49.209655276s


extracting reproducer from 1 programs
testing a last program of every proc
single: executing 1 programs separately with timeout 30s
testing program (duration=30s, {Threaded:true Repeat:true RepeatTimes:0 Procs:5 Slowdown:1 Sandbox:none SandboxArg:0 Leak:false NetInjection:true NetDevices:true NetReset:true Cgroups:true BinfmtMisc:true CloseFDs:true KCSAN:false DevlinkPCI:false NicVF:false USB:true VhciInjection:true Wifi:true IEEE802154:true Sysctl:true Swap:true UseTmpDir:true HandleSegv:true Trace:false CallComments:true LegacyOptions:{Collide:false Fault:false FaultCall:0 FaultNth:0}}): syz_usb_connect
detailed listing:
executing program 0:
syz_usb_connect(0x5, 0x2d, &(0x7f00000005c0)=ANY=[@ANYBLOB="9f01000083667d1040206502d14e0102030109021b000100000000090400000190f19c000905f3ede8e9384088477da5163aeacac5aef6b35899848f884763144ec6a2aeada635e54cdc8fb569daf4797849ac735823c41a718ab016b0c1ec7613250780", @ANYRESHEX=0x0, @ANYRESDEC=0x0, @ANYRESHEX, @ANYRES32, @ANYRES8=0x0], 0x0)

program did not crash
single: failed to extract reproducer
single: executing 1 programs separately with timeout 1m40s
testing program (duration=1m40s, {Threaded:true Repeat:true RepeatTimes:0 Procs:5 Slowdown:1 Sandbox:none SandboxArg:0 Leak:false NetInjection:true NetDevices:true NetReset:true Cgroups:true BinfmtMisc:true CloseFDs:true KCSAN:false DevlinkPCI:false NicVF:false USB:true VhciInjection:true Wifi:true IEEE802154:true Sysctl:true Swap:true UseTmpDir:true HandleSegv:true Trace:false CallComments:true LegacyOptions:{Collide:false Fault:false FaultCall:0 FaultNth:0}}): syz_usb_connect
detailed listing:
executing program 0:
syz_usb_connect(0x5, 0x2d, &(0x7f00000005c0)=ANY=[@ANYBLOB="9f01000083667d1040206502d14e0102030109021b000100000000090400000190f19c000905f3ede8e9384088477da5163aeacac5aef6b35899848f884763144ec6a2aeada635e54cdc8fb569daf4797849ac735823c41a718ab016b0c1ec7613250780", @ANYRESHEX=0x0, @ANYRESDEC=0x0, @ANYRESHEX, @ANYRES32, @ANYRES8=0x0], 0x0)

program crashed: KASAN: slab-use-after-free Read in em28xx_init_extension
single: successfully extracted reproducer
found reproducer with 1 syscalls
minimizing guilty program
testing program (duration=1m40s, {Threaded:true Repeat:true RepeatTimes:0 Procs:5 Slowdown:1 Sandbox:none SandboxArg:0 Leak:false NetInjection:true NetDevices:true NetReset:true Cgroups:true BinfmtMisc:true CloseFDs:true KCSAN:false DevlinkPCI:false NicVF:false USB:true VhciInjection:true Wifi:true IEEE802154:true Sysctl:true Swap:true UseTmpDir:true HandleSegv:true Trace:false CallComments:true LegacyOptions:{Collide:false Fault:false FaultCall:0 FaultNth:0}}): syz_usb_connect
detailed listing:
executing program 0:
syz_usb_connect(0x5, 0x2d, 0x0, 0x0)

program did not crash
testing program (duration=1m40s, {Threaded:true Repeat:true RepeatTimes:0 Procs:5 Slowdown:1 Sandbox:none SandboxArg:0 Leak:false NetInjection:true NetDevices:true NetReset:true Cgroups:true BinfmtMisc:true CloseFDs:true KCSAN:false DevlinkPCI:false NicVF:false USB:true VhciInjection:true Wifi:true IEEE802154:true Sysctl:true Swap:true UseTmpDir:true HandleSegv:true Trace:false CallComments:true LegacyOptions:{Collide:false Fault:false FaultCall:0 FaultNth:0}}): syz_usb_connect
detailed listing:
executing program 0:
syz_usb_connect(0x5, 0x2d, &(0x7f00000005c0)=ANY=[], 0x0)

program did not crash
testing program (duration=1m40s, {Threaded:true Repeat:true RepeatTimes:0 Procs:5 Slowdown:1 Sandbox:none SandboxArg:0 Leak:false NetInjection:true NetDevices:true NetReset:true Cgroups:true BinfmtMisc:true CloseFDs:true KCSAN:false DevlinkPCI:false NicVF:false USB:true VhciInjection:true Wifi:true IEEE802154:true Sysctl:true Swap:true UseTmpDir:true HandleSegv:true Trace:false CallComments:true LegacyOptions:{Collide:false Fault:false FaultCall:0 FaultNth:0}}): syz_usb_connect
detailed listing:
executing program 0:
syz_usb_connect(0x5, 0x2d, &(0x7f00000005c0)=ANY=[@ANYBLOB, @ANYRESHEX=0x0, @ANYRESDEC=0x0, @ANYRESHEX, @ANYRES32, @ANYRES8=0x0], 0x0)

program did not crash
extracting C reproducer
testing compiled C program (duration=1m40s, {Threaded:true Repeat:true RepeatTimes:0 Procs:5 Slowdown:1 Sandbox:none SandboxArg:0 Leak:false NetInjection:true NetDevices:true NetReset:true Cgroups:true BinfmtMisc:true CloseFDs:true KCSAN:false DevlinkPCI:false NicVF:false USB:true VhciInjection:true Wifi:true IEEE802154:true Sysctl:true Swap:true UseTmpDir:true HandleSegv:true Trace:false CallComments:true LegacyOptions:{Collide:false Fault:false FaultCall:0 FaultNth:0}}): syz_usb_connect
program crashed: KASAN: slab-use-after-free Read in em28xx_init_extension
simplifying C reproducer
testing compiled C program (duration=1m40s, {Threaded:false Repeat:true RepeatTimes:0 Procs:5 Slowdown:1 Sandbox:none SandboxArg:0 Leak:false NetInjection:true NetDevices:true NetReset:true Cgroups:true BinfmtMisc:true CloseFDs:true KCSAN:false DevlinkPCI:false NicVF:false USB:true VhciInjection:true Wifi:true IEEE802154:true Sysctl:true Swap:true UseTmpDir:true HandleSegv:true Trace:false CallComments:true LegacyOptions:{Collide:false Fault:false FaultCall:0 FaultNth:0}}): syz_usb_connect
program crashed: BUG: corrupted list in em28xx_init_extension
a never seen crash title: BUG: corrupted list in em28xx_init_extension, ignore
testing compiled C program (duration=1m40s, {Threaded:true Repeat:true RepeatTimes:0 Procs:1 Slowdown:1 Sandbox:none SandboxArg:0 Leak:false NetInjection:true NetDevices:true NetReset:true Cgroups:true BinfmtMisc:true CloseFDs:true KCSAN:false DevlinkPCI:false NicVF:false USB:true VhciInjection:true Wifi:true IEEE802154:true Sysctl:true Swap:true UseTmpDir:true HandleSegv:true Trace:false CallComments:true LegacyOptions:{Collide:false Fault:false FaultCall:0 FaultNth:0}}): syz_usb_connect
program crashed: BUG: corrupted list in em28xx_init_extension
a never seen crash title: BUG: corrupted list in em28xx_init_extension, ignore
testing compiled C program (duration=1m40s, {Threaded:true Repeat:true RepeatTimes:0 Procs:5 Slowdown:1 Sandbox: SandboxArg:0 Leak:false NetInjection:false NetDevices:false NetReset:false Cgroups:false BinfmtMisc:false CloseFDs:false KCSAN:false DevlinkPCI:false NicVF:false USB:false VhciInjection:false Wifi:false IEEE802154:true Sysctl:true Swap:false UseTmpDir:true HandleSegv:true Trace:false CallComments:true LegacyOptions:{Collide:false Fault:false FaultCall:0 FaultNth:0}}): syz_usb_connect
program crashed: KASAN: use-after-free Read in em28xx_init_extension
a never seen crash title: KASAN: use-after-free Read in em28xx_init_extension, ignore
testing compiled C program (duration=1m40s, {Threaded:true Repeat:true RepeatTimes:0 Procs:5 Slowdown:1 Sandbox:none SandboxArg:0 Leak:false NetInjection:false NetDevices:true NetReset:true Cgroups:true BinfmtMisc:true CloseFDs:true KCSAN:false DevlinkPCI:false NicVF:false USB:true VhciInjection:true Wifi:true IEEE802154:true Sysctl:true Swap:true UseTmpDir:true HandleSegv:true Trace:false CallComments:true LegacyOptions:{Collide:false Fault:false FaultCall:0 FaultNth:0}}): syz_usb_connect
program crashed: BUG: corrupted list in em28xx_init_extension
a never seen crash title: BUG: corrupted list in em28xx_init_extension, ignore
testing compiled C program (duration=1m40s, {Threaded:true Repeat:true RepeatTimes:0 Procs:5 Slowdown:1 Sandbox:none SandboxArg:0 Leak:false NetInjection:true NetDevices:false NetReset:true Cgroups:true BinfmtMisc:true CloseFDs:true KCSAN:false DevlinkPCI:false NicVF:false USB:true VhciInjection:true Wifi:true IEEE802154:true Sysctl:true Swap:true UseTmpDir:true HandleSegv:true Trace:false CallComments:true LegacyOptions:{Collide:false Fault:false FaultCall:0 FaultNth:0}}): syz_usb_connect
program crashed: KASAN: slab-use-after-free Read in em28xx_close_extension
a never seen crash title: KASAN: slab-use-after-free Read in em28xx_close_extension, ignore
testing compiled C program (duration=1m40s, {Threaded:true Repeat:true RepeatTimes:0 Procs:5 Slowdown:1 Sandbox:none SandboxArg:0 Leak:false NetInjection:true NetDevices:true NetReset:false Cgroups:true BinfmtMisc:true CloseFDs:true KCSAN:false DevlinkPCI:false NicVF:false USB:true VhciInjection:true Wifi:true IEEE802154:true Sysctl:true Swap:true UseTmpDir:true HandleSegv:true Trace:false CallComments:true LegacyOptions:{Collide:false Fault:false FaultCall:0 FaultNth:0}}): syz_usb_connect
program crashed: BUG: corrupted list in em28xx_init_extension
a never seen crash title: BUG: corrupted list in em28xx_init_extension, ignore
testing compiled C program (duration=1m40s, {Threaded:true Repeat:true RepeatTimes:0 Procs:5 Slowdown:1 Sandbox:none SandboxArg:0 Leak:false NetInjection:true NetDevices:true NetReset:true Cgroups:false BinfmtMisc:true CloseFDs:true KCSAN:false DevlinkPCI:false NicVF:false USB:true VhciInjection:true Wifi:true IEEE802154:true Sysctl:true Swap:true UseTmpDir:true HandleSegv:true Trace:false CallComments:true LegacyOptions:{Collide:false Fault:false FaultCall:0 FaultNth:0}}): syz_usb_connect
program crashed: KASAN: slab-out-of-bounds Read in em28xx_close_extension
a never seen crash title: KASAN: slab-out-of-bounds Read in em28xx_close_extension, ignore
testing compiled C program (duration=1m40s, {Threaded:true Repeat:true RepeatTimes:0 Procs:5 Slowdown:1 Sandbox:none SandboxArg:0 Leak:false NetInjection:true NetDevices:true NetReset:true Cgroups:true BinfmtMisc:false CloseFDs:true KCSAN:false DevlinkPCI:false NicVF:false USB:true VhciInjection:true Wifi:true IEEE802154:true Sysctl:true Swap:true UseTmpDir:true HandleSegv:true Trace:false CallComments:true LegacyOptions:{Collide:false Fault:false FaultCall:0 FaultNth:0}}): syz_usb_connect
program crashed: BUG: corrupted list in em28xx_close_extension
a never seen crash title: BUG: corrupted list in em28xx_close_extension, ignore
testing compiled C program (duration=1m40s, {Threaded:true Repeat:true RepeatTimes:0 Procs:5 Slowdown:1 Sandbox:none SandboxArg:0 Leak:false NetInjection:true NetDevices:true NetReset:true Cgroups:true BinfmtMisc:true CloseFDs:true KCSAN:false DevlinkPCI:false NicVF:false USB:false VhciInjection:true Wifi:true IEEE802154:true Sysctl:true Swap:true UseTmpDir:true HandleSegv:true Trace:false CallComments:true LegacyOptions:{Collide:false Fault:false FaultCall:0 FaultNth:0}}): syz_usb_connect
program crashed: BUG: corrupted list in em28xx_init_extension
a never seen crash title: BUG: corrupted list in em28xx_init_extension, ignore
testing compiled C program (duration=1m40s, {Threaded:true Repeat:true RepeatTimes:0 Procs:5 Slowdown:1 Sandbox:none SandboxArg:0 Leak:false NetInjection:true NetDevices:true NetReset:true Cgroups:true BinfmtMisc:true CloseFDs:true KCSAN:false DevlinkPCI:false NicVF:false USB:true VhciInjection:false Wifi:true IEEE802154:true Sysctl:true Swap:true UseTmpDir:true HandleSegv:true Trace:false CallComments:true LegacyOptions:{Collide:false Fault:false FaultCall:0 FaultNth:0}}): syz_usb_connect
program crashed: BUG: corrupted list in em28xx_close_extension
a never seen crash title: BUG: corrupted list in em28xx_close_extension, ignore
testing compiled C program (duration=1m40s, {Threaded:true Repeat:true RepeatTimes:0 Procs:5 Slowdown:1 Sandbox:none SandboxArg:0 Leak:false NetInjection:true NetDevices:true NetReset:true Cgroups:true BinfmtMisc:true CloseFDs:true KCSAN:false DevlinkPCI:false NicVF:false USB:true VhciInjection:true Wifi:false IEEE802154:true Sysctl:true Swap:true UseTmpDir:true HandleSegv:true Trace:false CallComments:true LegacyOptions:{Collide:false Fault:false FaultCall:0 FaultNth:0}}): syz_usb_connect
program crashed: BUG: corrupted list in em28xx_init_extension
a never seen crash title: BUG: corrupted list in em28xx_init_extension, ignore
testing compiled C program (duration=1m40s, {Threaded:true Repeat:true RepeatTimes:0 Procs:5 Slowdown:1 Sandbox:none SandboxArg:0 Leak:false NetInjection:true NetDevices:true NetReset:true Cgroups:true BinfmtMisc:true CloseFDs:true KCSAN:false DevlinkPCI:false NicVF:false USB:true VhciInjection:true Wifi:true IEEE802154:false Sysctl:true Swap:true UseTmpDir:true HandleSegv:true Trace:false CallComments:true LegacyOptions:{Collide:false Fault:false FaultCall:0 FaultNth:0}}): syz_usb_connect
program crashed: BUG: corrupted list in em28xx_close_extension
a never seen crash title: BUG: corrupted list in em28xx_close_extension, ignore
testing compiled C program (duration=1m40s, {Threaded:true Repeat:true RepeatTimes:0 Procs:5 Slowdown:1 Sandbox:none SandboxArg:0 Leak:false NetInjection:true NetDevices:true NetReset:true Cgroups:true BinfmtMisc:true CloseFDs:true KCSAN:false DevlinkPCI:false NicVF:false USB:true VhciInjection:true Wifi:true IEEE802154:true Sysctl:true Swap:true UseTmpDir:true HandleSegv:false Trace:false CallComments:true LegacyOptions:{Collide:false Fault:false FaultCall:0 FaultNth:0}}): syz_usb_connect
program crashed: BUG: corrupted list in em28xx_close_extension
a never seen crash title: BUG: corrupted list in em28xx_close_extension, ignore
testing compiled C program (duration=1m40s, {Threaded:true Repeat:true RepeatTimes:0 Procs:5 Slowdown:1 Sandbox:none SandboxArg:0 Leak:false NetInjection:true NetDevices:true NetReset:true Cgroups:true BinfmtMisc:true CloseFDs:true KCSAN:false DevlinkPCI:false NicVF:false USB:true VhciInjection:true Wifi:true IEEE802154:true Sysctl:false Swap:true UseTmpDir:true HandleSegv:true Trace:false CallComments:true LegacyOptions:{Collide:false Fault:false FaultCall:0 FaultNth:0}}): syz_usb_connect
program crashed: BUG: corrupted list in em28xx_close_extension
a never seen crash title: BUG: corrupted list in em28xx_close_extension, ignore
testing compiled C program (duration=1m40s, {Threaded:true Repeat:true RepeatTimes:0 Procs:5 Slowdown:1 Sandbox:none SandboxArg:0 Leak:false NetInjection:true NetDevices:true NetReset:true Cgroups:true BinfmtMisc:true CloseFDs:true KCSAN:false DevlinkPCI:false NicVF:false USB:true VhciInjection:true Wifi:true IEEE802154:true Sysctl:true Swap:false UseTmpDir:true HandleSegv:true Trace:false CallComments:true LegacyOptions:{Collide:false Fault:false FaultCall:0 FaultNth:0}}): syz_usb_connect
program crashed: KASAN: use-after-free Read in em28xx_init_extension
a never seen crash title: KASAN: use-after-free Read in em28xx_init_extension, ignore
testing program (duration=1m40s, {Threaded:true Repeat:true RepeatTimes:0 Procs:5 Slowdown:1 Sandbox:none SandboxArg:0 Leak:false NetInjection:true NetDevices:true NetReset:true Cgroups:true BinfmtMisc:true CloseFDs:true KCSAN:false DevlinkPCI:false NicVF:false USB:true VhciInjection:true Wifi:true IEEE802154:true Sysctl:true Swap:true UseTmpDir:true HandleSegv:true Trace:false CallComments:true LegacyOptions:{Collide:false Fault:false FaultCall:0 FaultNth:0}}): syz_usb_connect
detailed listing:
executing program 0:
syz_usb_connect(0x5, 0x2d, &(0x7f00000005c0)=ANY=[@ANYBLOB="9f01000083667d1040206502d14e0102030109021b000100000000090400000190f19c000905f3ede8e9384088477da5163aeacac5aef6b35899848f884763144ec6a2aeada635e54cdc8fb569daf4797849ac735823c41a718ab016b0c1ec7613250780", @ANYRESHEX=0x0, @ANYRESDEC=0x0, @ANYRESHEX, @ANYRES32, @ANYRES8=0x0], 0x0)

program crashed: KASAN: slab-out-of-bounds Read in em28xx_init_extension
validation run: crashed=true
testing program (duration=1m40s, {Threaded:true Repeat:true RepeatTimes:0 Procs:5 Slowdown:1 Sandbox:none SandboxArg:0 Leak:false NetInjection:true NetDevices:true NetReset:true Cgroups:true BinfmtMisc:true CloseFDs:true KCSAN:false DevlinkPCI:false NicVF:false USB:true VhciInjection:true Wifi:true IEEE802154:true Sysctl:true Swap:true UseTmpDir:true HandleSegv:true Trace:false CallComments:true LegacyOptions:{Collide:false Fault:false FaultCall:0 FaultNth:0}}): syz_usb_connect
detailed listing:
executing program 0:
syz_usb_connect(0x5, 0x2d, &(0x7f00000005c0)=ANY=[@ANYBLOB="9f01000083667d1040206502d14e0102030109021b000100000000090400000190f19c000905f3ede8e9384088477da5163aeacac5aef6b35899848f884763144ec6a2aeada635e54cdc8fb569daf4797849ac735823c41a718ab016b0c1ec7613250780", @ANYRESHEX=0x0, @ANYRESDEC=0x0, @ANYRESHEX, @ANYRES32, @ANYRES8=0x0], 0x0)

program crashed: BUG: corrupted list in em28xx_init_extension
validation run: crashed=true
testing program (duration=1m40s, {Threaded:true Repeat:true RepeatTimes:0 Procs:5 Slowdown:1 Sandbox:none SandboxArg:0 Leak:false NetInjection:true NetDevices:true NetReset:true Cgroups:true BinfmtMisc:true CloseFDs:true KCSAN:false DevlinkPCI:false NicVF:false USB:true VhciInjection:true Wifi:true IEEE802154:true Sysctl:true Swap:true UseTmpDir:true HandleSegv:true Trace:false CallComments:true LegacyOptions:{Collide:false Fault:false FaultCall:0 FaultNth:0}}): syz_usb_connect
detailed listing:
executing program 0:
syz_usb_connect(0x5, 0x2d, &(0x7f00000005c0)=ANY=[@ANYBLOB="9f01000083667d1040206502d14e0102030109021b000100000000090400000190f19c000905f3ede8e9384088477da5163aeacac5aef6b35899848f884763144ec6a2aeada635e54cdc8fb569daf4797849ac735823c41a718ab016b0c1ec7613250780", @ANYRESHEX=0x0, @ANYRESDEC=0x0, @ANYRESHEX, @ANYRES32, @ANYRES8=0x0], 0x0)

program crashed: KASAN: slab-use-after-free Read in em28xx_init_extension
validation run: crashed=true
reproducing took 40m5.428061453s
repro crashed as (corrupted=false):
em28xx 3-1:0.0: New device syz syz @ 480 Mbps (2040:0265, interface 0, class 0)
em28xx 3-1:0.0: Audio interface 0 found (Vendor Class)
em28xx 3-1:0.0: unknown em28xx chip ID (0)
em28xx 3-1:0.0: Config register raw data: 0xfffffffb
em28xx 3-1:0.0: AC97 chip type couldn't be determined
em28xx 3-1:0.0: No AC97 audio processor
==================================================================
BUG: KASAN: slab-use-after-free in __list_add_valid_or_report+0x6a/0x130 lib/list_debug.c:32
Read of size 8 at addr ffff8880474b8290 by task kworker/0:7/5996

CPU: 0 UID: 0 PID: 5996 Comm: kworker/0:7 Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Workqueue: usb_hub_wq hub_event
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 print_address_description+0x55/0x1e0 mm/kasan/report.c:378
 print_report+0x58/0x70 mm/kasan/report.c:482
 kasan_report+0x117/0x150 mm/kasan/report.c:595
 __list_add_valid_or_report+0x6a/0x130 lib/list_debug.c:32
 __list_add_valid include/linux/list.h:96 [inline]
 __list_add include/linux/list.h:158 [inline]
 list_add_tail include/linux/list.h:191 [inline]
 em28xx_init_extension+0x56/0x1d0 drivers/media/usb/em28xx/em28xx-core.c:1245
 em28xx_init_dev+0x9f6/0x2210 drivers/media/usb/em28xx/em28xx-cards.c:3887
 em28xx_usb_probe+0x17b2/0x2dd0 drivers/media/usb/em28xx/em28xx-cards.c:4258
 usb_probe_interface+0x653/0xc60 drivers/usb/core/driver.c:396
 call_driver_probe drivers/base/dd.c:-1 [inline]
 really_probe+0x254/0xae0 drivers/base/dd.c:706
 __driver_probe_device+0x1e8/0x360 drivers/base/dd.c:868
 driver_probe_device+0x4f/0x240 drivers/base/dd.c:898
 __device_attach_driver+0x270/0x410 drivers/base/dd.c:1026
 bus_for_each_drv+0x25b/0x2f0 drivers/base/bus.c:500
 __device_attach+0x2c7/0x450 drivers/base/dd.c:1098
 device_initial_probe+0xa1/0xd0 drivers/base/dd.c:1153
 bus_probe_device+0x12d/0x220 drivers/base/bus.c:620
 device_add+0x7d7/0xb80 drivers/base/core.c:3772
 usb_set_configuration+0x1ad8/0x2180 drivers/usb/core/message.c:2268
 usb_generic_driver_probe+0x8d/0x150 drivers/usb/core/generic.c:250
 usb_probe_device+0x1c3/0x3b0 drivers/usb/core/driver.c:291
 call_driver_probe drivers/base/dd.c:-1 [inline]
 really_probe+0x254/0xae0 drivers/base/dd.c:706
 __driver_probe_device+0x1e8/0x360 drivers/base/dd.c:868
 driver_probe_device+0x4f/0x240 drivers/base/dd.c:898
 __device_attach_driver+0x270/0x410 drivers/base/dd.c:1026
 bus_for_each_drv+0x25b/0x2f0 drivers/base/bus.c:500
 __device_attach+0x2c7/0x450 drivers/base/dd.c:1098
 device_initial_probe+0xa1/0xd0 drivers/base/dd.c:1153
 bus_probe_device+0x12d/0x220 drivers/base/bus.c:620
 device_add+0x7d7/0xb80 drivers/base/core.c:3772
 usb_new_device+0x99a/0x1680 drivers/usb/core/hub.c:2703
 hub_port_connect drivers/usb/core/hub.c:5575 [inline]
 hub_port_connect_change drivers/usb/core/hub.c:5715 [inline]
 port_event drivers/usb/core/hub.c:5879 [inline]
 hub_event+0x28cf/0x4cf0 drivers/usb/core/hub.c:5961
 process_one_work kernel/workqueue.c:3322 [inline]
 process_scheduled_works+0xa8e/0x14e0 kernel/workqueue.c:3405
 worker_thread+0xa47/0xfb0 kernel/workqueue.c:3486
 kthread+0x388/0x470 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>

Allocated by task 13:
 kasan_save_stack mm/kasan/common.c:57 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
 unpoison_slab_object mm/kasan/common.c:340 [inline]
 __kasan_slab_alloc+0x6c/0x80 mm/kasan/common.c:366
 kasan_slab_alloc include/linux/kasan.h:253 [inline]
 slab_post_alloc_hook mm/slub.c:4584 [inline]
 slab_alloc_node mm/slub.c:4917 [inline]
 kmem_cache_alloc_node_noprof+0x3eb/0x670 mm/slub.c:4989
 kmalloc_reserve net/core/skbuff.c:615 [inline]
 __alloc_skb+0x276/0x7a0 net/core/skbuff.c:715
 alloc_skb include/linux/skbuff.h:1384 [inline]
 nlmsg_new include/net/netlink.h:1055 [inline]
 inet6_ifa_notify net/ipv6/addrconf.c:5645 [inline]
 __ipv6_ifa_notify+0x1d0/0xc60 net/ipv6/addrconf.c:6305
 ipv6_ifa_notify net/ipv6/addrconf.c:6357 [inline]
 addrconf_dad_completed+0x1b5/0xe60 net/ipv6/addrconf.c:4355
 addrconf_dad_work+0xdda/0x16e0 net/ipv6/addrconf.c:-1
 process_one_work kernel/workqueue.c:3322 [inline]
 process_scheduled_works+0xa8e/0x14e0 kernel/workqueue.c:3405
 worker_thread+0xa47/0xfb0 kernel/workqueue.c:3486
 kthread+0x388/0x470 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

Freed by task 13:
 kasan_save_stack mm/kasan/common.c:57 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
 kasan_save_free_info+0x40/0x50 mm/kasan/generic.c:584
 poison_slab_object mm/kasan/common.c:253 [inline]
 __kasan_slab_free+0x5c/0x80 mm/kasan/common.c:285
 kasan_slab_free include/linux/kasan.h:235 [inline]
 slab_free_hook mm/slub.c:2677 [inline]
 slab_free mm/slub.c:6377 [inline]
 kfree+0x1c5/0x6c0 mm/slub.c:6692
 skb_kfree_head net/core/skbuff.c:1083 [inline]
 skb_free_head net/core/skbuff.c:1095 [inline]
 skb_release_data+0x85e/0xab0 net/core/skbuff.c:1122
 skb_release_all net/core/skbuff.c:1197 [inline]
 __kfree_skb+0x5d/0x210 net/core/skbuff.c:1211
 netlink_broadcast_filtered+0xd97/0xea0 net/netlink/af_netlink.c:1541
 nlmsg_multicast_filtered include/net/netlink.h:1165 [inline]
 nlmsg_multicast include/net/netlink.h:1184 [inline]
 nlmsg_notify+0xe3/0x1a0 net/netlink/af_netlink.c:2599
 inet6_ifa_notify net/ipv6/addrconf.c:5656 [inline]
 __ipv6_ifa_notify+0x21e/0xc60 net/ipv6/addrconf.c:6305
 ipv6_ifa_notify net/ipv6/addrconf.c:6357 [inline]
 addrconf_dad_completed+0x1b5/0xe60 net/ipv6/addrconf.c:4355
 addrconf_dad_work+0xdda/0x16e0 net/ipv6/addrconf.c:-1
 process_one_work kernel/workqueue.c:3322 [inline]
 process_scheduled_works+0xa8e/0x14e0 kernel/workqueue.c:3405
 worker_thread+0xa47/0xfb0 kernel/workqueue.c:3486
 kthread+0x388/0x470 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

The buggy address belongs to the object at ffff8880474b8000
 which belongs to the cache skbuff_small_head of size 704
The buggy address is located 656 bytes inside of
 freed 704-byte region [ffff8880474b8000, ffff8880474b82c0)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x474b8
head: order:2 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0x80000000000040(head|node=0|zone=1)
page_type: f5(slab)
raw: 0080000000000040 ffff88801ceeec80 dead000000000100 dead000000000122
raw: 0000000000000000 0000000800130013 00000000f5000000 0000000000000000
head: 0080000000000040 ffff88801ceeec80 dead000000000100 dead000000000122
head: 0000000000000000 0000000800130013 00000000f5000000 0000000000000000
head: 0080000000000002 ffffffffffffff01 00000000ffffffff 00000000ffffffff
head: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000004
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 2, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 5729, tgid 5729 (syz-executor), ts 133555957054, free_ts 133502109494
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x1f9/0x250 mm/page_alloc.c:1859
 prep_new_page mm/page_alloc.c:1867 [inline]
 get_page_from_freelist+0x262a/0x26a0 mm/page_alloc.c:3946
 __alloc_frozen_pages_noprof+0x18d/0x380 mm/page_alloc.c:5304
 alloc_slab_page mm/slub.c:3266 [inline]
 allocate_slab+0x79/0x5e0 mm/slub.c:3380
 new_slab mm/slub.c:3426 [inline]
 refill_objects+0x2d8/0x350 mm/slub.c:7310
 refill_sheaf mm/slub.c:2804 [inline]
 __pcs_replace_empty_main+0x330/0x690 mm/slub.c:4675
 alloc_from_pcs mm/slub.c:4773 [inline]
 slab_alloc_node mm/slub.c:4905 [inline]
 kmem_cache_alloc_node_noprof+0x4dc/0x670 mm/slub.c:4989
 kmalloc_reserve net/core/skbuff.c:615 [inline]
 __alloc_skb+0x276/0x7a0 net/core/skbuff.c:715
 netlink_sendmsg+0x5d4/0xb40 net/netlink/af_netlink.c:1875
 sock_sendmsg_nosec+0x13a/0x180 net/socket.c:775
 __sock_sendmsg net/socket.c:790 [inline]
 __sys_sendto+0x41e/0x5d0 net/socket.c:2252
 __do_sys_sendto net/socket.c:2259 [inline]
 __se_sys_sendto net/socket.c:2255 [inline]
 __x64_sys_sendto+0xde/0x100 net/socket.c:2255
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
page last free pid 10 tgid 10 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 __free_pages_prepare mm/page_alloc.c:1406 [inline]
 __free_frozen_pages+0x10e7/0x11c0 mm/page_alloc.c:2950
 kref_put include/linux/kref.h:65 [inline]
 em28xx_usb_disconnect+0x27f/0x2f0 drivers/media/usb/em28xx/em28xx-cards.c:4430
 usb_unbind_interface+0x295/0x9f0 drivers/usb/core/driver.c:458
 device_remove drivers/base/dd.c:618 [inline]
 __device_release_driver drivers/base/dd.c:1349 [inline]
 device_release_driver_internal+0x4f5/0x880 drivers/base/dd.c:1372
 bus_remove_device+0x449/0x560 drivers/base/bus.c:664
 device_del+0x528/0x8f0 drivers/base/core.c:3961
 usb_disable_device+0x3d4/0x8d0 drivers/usb/core/message.c:1478
 usb_disconnect+0x32d/0x990 drivers/usb/core/hub.c:2345
 hub_port_connect drivers/usb/core/hub.c:5415 [inline]
 hub_port_connect_change drivers/usb/core/hub.c:5715 [inline]
 port_event drivers/usb/core/hub.c:5879 [inline]
 hub_event+0x1bb7/0x4cf0 drivers/usb/core/hub.c:5961
 process_one_work kernel/workqueue.c:3322 [inline]
 process_scheduled_works+0xa8e/0x14e0 kernel/workqueue.c:3405
 worker_thread+0xa47/0xfb0 kernel/workqueue.c:3486
 kthread+0x388/0x470 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

Memory state around the buggy address:
 ffff8880474b8180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8880474b8200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8880474b8280: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
                         ^
 ffff8880474b8300: fc fc fc fc fc fc fc fc fa fb fb fb fb fb fb fb
 ffff8880474b8380: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

final repro crashed as (corrupted=false):
em28xx 3-1:0.0: New device syz syz @ 480 Mbps (2040:0265, interface 0, class 0)
em28xx 3-1:0.0: Audio interface 0 found (Vendor Class)
em28xx 3-1:0.0: unknown em28xx chip ID (0)
em28xx 3-1:0.0: Config register raw data: 0xfffffffb
em28xx 3-1:0.0: AC97 chip type couldn't be determined
em28xx 3-1:0.0: No AC97 audio processor
==================================================================
BUG: KASAN: slab-use-after-free in __list_add_valid_or_report+0x6a/0x130 lib/list_debug.c:32
Read of size 8 at addr ffff8880474b8290 by task kworker/0:7/5996

CPU: 0 UID: 0 PID: 5996 Comm: kworker/0:7 Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Workqueue: usb_hub_wq hub_event
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 print_address_description+0x55/0x1e0 mm/kasan/report.c:378
 print_report+0x58/0x70 mm/kasan/report.c:482
 kasan_report+0x117/0x150 mm/kasan/report.c:595
 __list_add_valid_or_report+0x6a/0x130 lib/list_debug.c:32
 __list_add_valid include/linux/list.h:96 [inline]
 __list_add include/linux/list.h:158 [inline]
 list_add_tail include/linux/list.h:191 [inline]
 em28xx_init_extension+0x56/0x1d0 drivers/media/usb/em28xx/em28xx-core.c:1245
 em28xx_init_dev+0x9f6/0x2210 drivers/media/usb/em28xx/em28xx-cards.c:3887
 em28xx_usb_probe+0x17b2/0x2dd0 drivers/media/usb/em28xx/em28xx-cards.c:4258
 usb_probe_interface+0x653/0xc60 drivers/usb/core/driver.c:396
 call_driver_probe drivers/base/dd.c:-1 [inline]
 really_probe+0x254/0xae0 drivers/base/dd.c:706
 __driver_probe_device+0x1e8/0x360 drivers/base/dd.c:868
 driver_probe_device+0x4f/0x240 drivers/base/dd.c:898
 __device_attach_driver+0x270/0x410 drivers/base/dd.c:1026
 bus_for_each_drv+0x25b/0x2f0 drivers/base/bus.c:500
 __device_attach+0x2c7/0x450 drivers/base/dd.c:1098
 device_initial_probe+0xa1/0xd0 drivers/base/dd.c:1153
 bus_probe_device+0x12d/0x220 drivers/base/bus.c:620
 device_add+0x7d7/0xb80 drivers/base/core.c:3772
 usb_set_configuration+0x1ad8/0x2180 drivers/usb/core/message.c:2268
 usb_generic_driver_probe+0x8d/0x150 drivers/usb/core/generic.c:250
 usb_probe_device+0x1c3/0x3b0 drivers/usb/core/driver.c:291
 call_driver_probe drivers/base/dd.c:-1 [inline]
 really_probe+0x254/0xae0 drivers/base/dd.c:706
 __driver_probe_device+0x1e8/0x360 drivers/base/dd.c:868
 driver_probe_device+0x4f/0x240 drivers/base/dd.c:898
 __device_attach_driver+0x270/0x410 drivers/base/dd.c:1026
 bus_for_each_drv+0x25b/0x2f0 drivers/base/bus.c:500
 __device_attach+0x2c7/0x450 drivers/base/dd.c:1098
 device_initial_probe+0xa1/0xd0 drivers/base/dd.c:1153
 bus_probe_device+0x12d/0x220 drivers/base/bus.c:620
 device_add+0x7d7/0xb80 drivers/base/core.c:3772
 usb_new_device+0x99a/0x1680 drivers/usb/core/hub.c:2703
 hub_port_connect drivers/usb/core/hub.c:5575 [inline]
 hub_port_connect_change drivers/usb/core/hub.c:5715 [inline]
 port_event drivers/usb/core/hub.c:5879 [inline]
 hub_event+0x28cf/0x4cf0 drivers/usb/core/hub.c:5961
 process_one_work kernel/workqueue.c:3322 [inline]
 process_scheduled_works+0xa8e/0x14e0 kernel/workqueue.c:3405
 worker_thread+0xa47/0xfb0 kernel/workqueue.c:3486
 kthread+0x388/0x470 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>

Allocated by task 13:
 kasan_save_stack mm/kasan/common.c:57 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
 unpoison_slab_object mm/kasan/common.c:340 [inline]
 __kasan_slab_alloc+0x6c/0x80 mm/kasan/common.c:366
 kasan_slab_alloc include/linux/kasan.h:253 [inline]
 slab_post_alloc_hook mm/slub.c:4584 [inline]
 slab_alloc_node mm/slub.c:4917 [inline]
 kmem_cache_alloc_node_noprof+0x3eb/0x670 mm/slub.c:4989
 kmalloc_reserve net/core/skbuff.c:615 [inline]
 __alloc_skb+0x276/0x7a0 net/core/skbuff.c:715
 alloc_skb include/linux/skbuff.h:1384 [inline]
 nlmsg_new include/net/netlink.h:1055 [inline]
 inet6_ifa_notify net/ipv6/addrconf.c:5645 [inline]
 __ipv6_ifa_notify+0x1d0/0xc60 net/ipv6/addrconf.c:6305
 ipv6_ifa_notify net/ipv6/addrconf.c:6357 [inline]
 addrconf_dad_completed+0x1b5/0xe60 net/ipv6/addrconf.c:4355
 addrconf_dad_work+0xdda/0x16e0 net/ipv6/addrconf.c:-1
 process_one_work kernel/workqueue.c:3322 [inline]
 process_scheduled_works+0xa8e/0x14e0 kernel/workqueue.c:3405
 worker_thread+0xa47/0xfb0 kernel/workqueue.c:3486
 kthread+0x388/0x470 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

Freed by task 13:
 kasan_save_stack mm/kasan/common.c:57 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
 kasan_save_free_info+0x40/0x50 mm/kasan/generic.c:584
 poison_slab_object mm/kasan/common.c:253 [inline]
 __kasan_slab_free+0x5c/0x80 mm/kasan/common.c:285
 kasan_slab_free include/linux/kasan.h:235 [inline]
 slab_free_hook mm/slub.c:2677 [inline]
 slab_free mm/slub.c:6377 [inline]
 kfree+0x1c5/0x6c0 mm/slub.c:6692
 skb_kfree_head net/core/skbuff.c:1083 [inline]
 skb_free_head net/core/skbuff.c:1095 [inline]
 skb_release_data+0x85e/0xab0 net/core/skbuff.c:1122
 skb_release_all net/core/skbuff.c:1197 [inline]
 __kfree_skb+0x5d/0x210 net/core/skbuff.c:1211
 netlink_broadcast_filtered+0xd97/0xea0 net/netlink/af_netlink.c:1541
 nlmsg_multicast_filtered include/net/netlink.h:1165 [inline]
 nlmsg_multicast include/net/netlink.h:1184 [inline]
 nlmsg_notify+0xe3/0x1a0 net/netlink/af_netlink.c:2599
 inet6_ifa_notify net/ipv6/addrconf.c:5656 [inline]
 __ipv6_ifa_notify+0x21e/0xc60 net/ipv6/addrconf.c:6305
 ipv6_ifa_notify net/ipv6/addrconf.c:6357 [inline]
 addrconf_dad_completed+0x1b5/0xe60 net/ipv6/addrconf.c:4355
 addrconf_dad_work+0xdda/0x16e0 net/ipv6/addrconf.c:-1
 process_one_work kernel/workqueue.c:3322 [inline]
 process_scheduled_works+0xa8e/0x14e0 kernel/workqueue.c:3405
 worker_thread+0xa47/0xfb0 kernel/workqueue.c:3486
 kthread+0x388/0x470 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

The buggy address belongs to the object at ffff8880474b8000
 which belongs to the cache skbuff_small_head of size 704
The buggy address is located 656 bytes inside of
 freed 704-byte region [ffff8880474b8000, ffff8880474b82c0)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x474b8
head: order:2 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0x80000000000040(head|node=0|zone=1)
page_type: f5(slab)
raw: 0080000000000040 ffff88801ceeec80 dead000000000100 dead000000000122
raw: 0000000000000000 0000000800130013 00000000f5000000 0000000000000000
head: 0080000000000040 ffff88801ceeec80 dead000000000100 dead000000000122
head: 0000000000000000 0000000800130013 00000000f5000000 0000000000000000
head: 0080000000000002 ffffffffffffff01 00000000ffffffff 00000000ffffffff
head: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000004
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 2, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 5729, tgid 5729 (syz-executor), ts 133555957054, free_ts 133502109494
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x1f9/0x250 mm/page_alloc.c:1859
 prep_new_page mm/page_alloc.c:1867 [inline]
 get_page_from_freelist+0x262a/0x26a0 mm/page_alloc.c:3946
 __alloc_frozen_pages_noprof+0x18d/0x380 mm/page_alloc.c:5304
 alloc_slab_page mm/slub.c:3266 [inline]
 allocate_slab+0x79/0x5e0 mm/slub.c:3380
 new_slab mm/slub.c:3426 [inline]
 refill_objects+0x2d8/0x350 mm/slub.c:7310
 refill_sheaf mm/slub.c:2804 [inline]
 __pcs_replace_empty_main+0x330/0x690 mm/slub.c:4675
 alloc_from_pcs mm/slub.c:4773 [inline]
 slab_alloc_node mm/slub.c:4905 [inline]
 kmem_cache_alloc_node_noprof+0x4dc/0x670 mm/slub.c:4989
 kmalloc_reserve net/core/skbuff.c:615 [inline]
 __alloc_skb+0x276/0x7a0 net/core/skbuff.c:715
 netlink_sendmsg+0x5d4/0xb40 net/netlink/af_netlink.c:1875
 sock_sendmsg_nosec+0x13a/0x180 net/socket.c:775
 __sock_sendmsg net/socket.c:790 [inline]
 __sys_sendto+0x41e/0x5d0 net/socket.c:2252
 __do_sys_sendto net/socket.c:2259 [inline]
 __se_sys_sendto net/socket.c:2255 [inline]
 __x64_sys_sendto+0xde/0x100 net/socket.c:2255
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
page last free pid 10 tgid 10 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 __free_pages_prepare mm/page_alloc.c:1406 [inline]
 __free_frozen_pages+0x10e7/0x11c0 mm/page_alloc.c:2950
 kref_put include/linux/kref.h:65 [inline]
 em28xx_usb_disconnect+0x27f/0x2f0 drivers/media/usb/em28xx/em28xx-cards.c:4430
 usb_unbind_interface+0x295/0x9f0 drivers/usb/core/driver.c:458
 device_remove drivers/base/dd.c:618 [inline]
 __device_release_driver drivers/base/dd.c:1349 [inline]
 device_release_driver_internal+0x4f5/0x880 drivers/base/dd.c:1372
 bus_remove_device+0x449/0x560 drivers/base/bus.c:664
 device_del+0x528/0x8f0 drivers/base/core.c:3961
 usb_disable_device+0x3d4/0x8d0 drivers/usb/core/message.c:1478
 usb_disconnect+0x32d/0x990 drivers/usb/core/hub.c:2345
 hub_port_connect drivers/usb/core/hub.c:5415 [inline]
 hub_port_connect_change drivers/usb/core/hub.c:5715 [inline]
 port_event drivers/usb/core/hub.c:5879 [inline]
 hub_event+0x1bb7/0x4cf0 drivers/usb/core/hub.c:5961
 process_one_work kernel/workqueue.c:3322 [inline]
 process_scheduled_works+0xa8e/0x14e0 kernel/workqueue.c:3405
 worker_thread+0xa47/0xfb0 kernel/workqueue.c:3486
 kthread+0x388/0x470 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

Memory state around the buggy address:
 ffff8880474b8180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8880474b8200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8880474b8280: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
                         ^
 ffff8880474b8300: fc fc fc fc fc fc fc fc fa fb fb fb fb fb fb fb
 ffff8880474b8380: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================