Extracting prog: 3m36.35287119s
Minimizing prog: 1m58.479405761s
Simplifying prog options: 0s
Extracting C: 29.192217028s
Simplifying C: 8m15.774550804s


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 LegacyOptions:{Collide:false Fault:false FaultCall:0 FaultNth:0}}): syz_usb_connect
detailed listing:
executing program 0:
syz_usb_connect(0x0, 0x2d, &(0x7f0000000480)={{0x12, 0x1, 0x0, 0x78, 0x6c, 0xb3, 0x40, 0x424, 0xc001, 0x7fee, 0x0, 0x0, 0x0, 0x1, [{{0x9, 0x2, 0x1b, 0x1, 0x0, 0x0, 0x30, 0x0, [{{0x9, 0x4, 0xe6, 0x0, 0x1, 0x5c, 0xd5, 0xfd, 0x0, [], [{{0x9, 0x5, 0x4, 0xc, 0x400, 0x63, 0x9, 0x3}}]}}]}}]}}, 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 LegacyOptions:{Collide:false Fault:false FaultCall:0 FaultNth:0}}): syz_usb_connect
detailed listing:
executing program 0:
syz_usb_connect(0x0, 0x2d, &(0x7f0000000480)={{0x12, 0x1, 0x0, 0x78, 0x6c, 0xb3, 0x40, 0x424, 0xc001, 0x7fee, 0x0, 0x0, 0x0, 0x1, [{{0x9, 0x2, 0x1b, 0x1, 0x0, 0x0, 0x30, 0x0, [{{0x9, 0x4, 0xe6, 0x0, 0x1, 0x5c, 0xd5, 0xfd, 0x0, [], [{{0x9, 0x5, 0x4, 0xc, 0x400, 0x63, 0x9, 0x3}}]}}]}}]}}, 0x0)

program crashed: KASAN: slab-use-after-free Read in hdm_disconnect
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 LegacyOptions:{Collide:false Fault:false FaultCall:0 FaultNth:0}}): syz_usb_connect
detailed listing:
executing program 0:
syz_usb_connect(0x0, 0x0, 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 LegacyOptions:{Collide:false Fault:false FaultCall:0 FaultNth:0}}): syz_usb_connect
program crashed: KASAN: slab-use-after-free Read in hdm_disconnect
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 LegacyOptions:{Collide:false Fault:false FaultCall:0 FaultNth:0}}): syz_usb_connect
program crashed: KASAN: slab-use-after-free Read in hdm_disconnect
testing compiled C program (duration=1m40s, {Threaded:false 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 LegacyOptions:{Collide:false Fault:false FaultCall:0 FaultNth:0}}): syz_usb_connect
program crashed: KASAN: slab-use-after-free Read in hdm_disconnect
testing compiled C program (duration=1m40s, {Threaded:false Repeat:true RepeatTimes:0 Procs:1 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 LegacyOptions:{Collide:false Fault:false FaultCall:0 FaultNth:0}}): syz_usb_connect
program crashed: KASAN: slab-use-after-free Read in hdm_disconnect
testing compiled C program (duration=1m40s, {Threaded:false Repeat:true RepeatTimes:0 Procs:1 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:false Sysctl:true Swap:false UseTmpDir:true HandleSegv:true Trace:false LegacyOptions:{Collide:false Fault:false FaultCall:0 FaultNth:0}}): syz_usb_connect
program crashed: KASAN: slab-use-after-free Read in hdm_disconnect
testing compiled C program (duration=1m40s, {Threaded:false Repeat:true RepeatTimes:0 Procs:1 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:false Sysctl:true Swap:false UseTmpDir:false HandleSegv:true Trace:false LegacyOptions:{Collide:false Fault:false FaultCall:0 FaultNth:0}}): syz_usb_connect
program crashed: KASAN: slab-use-after-free Read in hdm_disconnect
testing compiled C program (duration=1m40s, {Threaded:false Repeat:true RepeatTimes:0 Procs:1 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:false Sysctl:true Swap:false UseTmpDir:false HandleSegv:false Trace:false LegacyOptions:{Collide:false Fault:false FaultCall:0 FaultNth:0}}): syz_usb_connect
program crashed: KASAN: slab-use-after-free Read in hdm_disconnect
testing compiled C program (duration=1m40s, {Threaded:false Repeat:true RepeatTimes:0 Procs:1 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:false Sysctl:false Swap:false UseTmpDir:false HandleSegv:false Trace:false LegacyOptions:{Collide:false Fault:false FaultCall:0 FaultNth:0}}): syz_usb_connect
program crashed: KASAN: slab-use-after-free Read in hdm_disconnect
testing program (duration=1m40s, {Threaded:false Repeat:true RepeatTimes:0 Procs:1 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:false Sysctl:false Swap:false UseTmpDir:false HandleSegv:false Trace:false LegacyOptions:{Collide:false Fault:false FaultCall:0 FaultNth:0}}): syz_usb_connect
detailed listing:
executing program 0:
syz_usb_connect(0x0, 0x2d, &(0x7f0000000480)={{0x12, 0x1, 0x0, 0x78, 0x6c, 0xb3, 0x40, 0x424, 0xc001, 0x7fee, 0x0, 0x0, 0x0, 0x1, [{{0x9, 0x2, 0x1b, 0x1, 0x0, 0x0, 0x30, 0x0, [{{0x9, 0x4, 0xe6, 0x0, 0x1, 0x5c, 0xd5, 0xfd, 0x0, [], [{{0x9, 0x5, 0x4, 0xc, 0x400, 0x63, 0x9, 0x3}}]}}]}}]}}, 0x0)

program crashed: KASAN: slab-use-after-free Read in hdm_disconnect
validation run: crashed=true
testing program (duration=1m40s, {Threaded:false Repeat:true RepeatTimes:0 Procs:1 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:false Sysctl:false Swap:false UseTmpDir:false HandleSegv:false Trace:false LegacyOptions:{Collide:false Fault:false FaultCall:0 FaultNth:0}}): syz_usb_connect
detailed listing:
executing program 0:
syz_usb_connect(0x0, 0x2d, &(0x7f0000000480)={{0x12, 0x1, 0x0, 0x78, 0x6c, 0xb3, 0x40, 0x424, 0xc001, 0x7fee, 0x0, 0x0, 0x0, 0x1, [{{0x9, 0x2, 0x1b, 0x1, 0x0, 0x0, 0x30, 0x0, [{{0x9, 0x4, 0xe6, 0x0, 0x1, 0x5c, 0xd5, 0xfd, 0x0, [], [{{0x9, 0x5, 0x4, 0xc, 0x400, 0x63, 0x9, 0x3}}]}}]}}]}}, 0x0)

program crashed: KASAN: slab-use-after-free Read in hdm_disconnect
validation run: crashed=true
testing program (duration=1m40s, {Threaded:false Repeat:true RepeatTimes:0 Procs:1 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:false Sysctl:false Swap:false UseTmpDir:false HandleSegv:false Trace:false LegacyOptions:{Collide:false Fault:false FaultCall:0 FaultNth:0}}): syz_usb_connect
detailed listing:
executing program 0:
syz_usb_connect(0x0, 0x2d, &(0x7f0000000480)={{0x12, 0x1, 0x0, 0x78, 0x6c, 0xb3, 0x40, 0x424, 0xc001, 0x7fee, 0x0, 0x0, 0x0, 0x1, [{{0x9, 0x2, 0x1b, 0x1, 0x0, 0x0, 0x30, 0x0, [{{0x9, 0x4, 0xe6, 0x0, 0x1, 0x5c, 0xd5, 0xfd, 0x0, [], [{{0x9, 0x5, 0x4, 0xc, 0x400, 0x63, 0x9, 0x3}}]}}]}}]}}, 0x0)

program crashed: KASAN: slab-use-after-free Read in hdm_disconnect
validation run: crashed=true
reproducing took 18m26.595823462s
repro crashed as (corrupted=false):
usb 1-1: config 0 descriptor??
usb 1-1: USB disconnect, device number 2
==================================================================
BUG: KASAN: slab-use-after-free in hdm_disconnect+0xf4/0x18c drivers/most/most_usb.c:1125
Read of size 8 at addr ffff0000d6c398a8 by task kworker/0:0/9

CPU: 0 UID: 0 PID: 9 Comm: kworker/0:0 Not tainted 6.16.0-rc7-syzkaller-g82af5ea7c611 #0 PREEMPT 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Workqueue: usb_hub_wq hub_event
Call trace:
 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:499 (C)
 __dump_stack+0x30/0x40 lib/dump_stack.c:94
 dump_stack_lvl+0xd8/0x12c lib/dump_stack.c:120
 print_address_description+0xa8/0x220 mm/kasan/report.c:378
 print_report+0x68/0x84 mm/kasan/report.c:480
 kasan_report+0xb0/0x110 mm/kasan/report.c:593
 __asan_report_load8_noabort+0x20/0x2c mm/kasan/report_generic.c:381
 hdm_disconnect+0xf4/0x18c drivers/most/most_usb.c:1125
 usb_unbind_interface+0x244/0x7c8 drivers/usb/core/driver.c:458
 device_remove drivers/base/dd.c:569 [inline]
 __device_release_driver drivers/base/dd.c:1272 [inline]
 device_release_driver_internal+0x3f8/0x658 drivers/base/dd.c:1295
 device_release_driver+0x28/0x38 drivers/base/dd.c:1318
 bus_remove_device+0x310/0x3b0 drivers/base/bus.c:579
 device_del+0x47c/0x808 drivers/base/core.c:3881
 usb_disable_device+0x33c/0x780 drivers/usb/core/message.c:1418
 usb_disconnect+0x284/0x82c drivers/usb/core/hub.c:2344
 hub_port_connect drivers/usb/core/hub.c:5406 [inline]
 hub_port_connect_change drivers/usb/core/hub.c:5706 [inline]
 port_event drivers/usb/core/hub.c:5870 [inline]
 hub_event+0x1688/0x3c78 drivers/usb/core/hub.c:5952
 process_one_work+0x7e8/0x155c kernel/workqueue.c:3238
 process_scheduled_works kernel/workqueue.c:3321 [inline]
 worker_thread+0x958/0xed8 kernel/workqueue.c:3402
 kthread+0x5fc/0x75c kernel/kthread.c:464
 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:844

Allocated by task 9:
 kasan_save_stack mm/kasan/common.c:47 [inline]
 kasan_save_track+0x40/0x78 mm/kasan/common.c:68
 kasan_save_alloc_info+0x44/0x54 mm/kasan/generic.c:562
 poison_kmalloc_redzone mm/kasan/common.c:377 [inline]
 __kasan_kmalloc+0x9c/0xb4 mm/kasan/common.c:394
 kasan_kmalloc include/linux/kasan.h:260 [inline]
 __kmalloc_cache_noprof+0x2a4/0x3fc mm/slub.c:4359
 kmalloc_noprof include/linux/slab.h:905 [inline]
 kzalloc_noprof include/linux/slab.h:1039 [inline]
 hdm_probe+0x9c/0x1044 drivers/most/most_usb.c:959
 usb_probe_interface+0x584/0xa44 drivers/usb/core/driver.c:396
 call_driver_probe drivers/base/dd.c:-1 [inline]
 really_probe+0x394/0x910 drivers/base/dd.c:657
 __driver_probe_device+0x180/0x2d4 drivers/base/dd.c:799
 driver_probe_device+0x78/0x330 drivers/base/dd.c:829
 __device_attach_driver+0x290/0x4e0 drivers/base/dd.c:957
 bus_for_each_drv+0x220/0x2b4 drivers/base/bus.c:462
 __device_attach+0x26c/0x388 drivers/base/dd.c:1029
 device_initial_probe+0x24/0x34 drivers/base/dd.c:1078
 bus_probe_device+0x178/0x240 drivers/base/bus.c:537
 device_add+0x71c/0xa60 drivers/base/core.c:3692
 usb_set_configuration+0x1640/0x1bac drivers/usb/core/message.c:2210
 usb_generic_driver_probe+0x8c/0x144 drivers/usb/core/generic.c:250
 usb_probe_device+0x1a4/0x348 drivers/usb/core/driver.c:291
 call_driver_probe drivers/base/dd.c:-1 [inline]
 really_probe+0x394/0x910 drivers/base/dd.c:657
 __driver_probe_device+0x180/0x2d4 drivers/base/dd.c:799
 driver_probe_device+0x78/0x330 drivers/base/dd.c:829
 __device_attach_driver+0x290/0x4e0 drivers/base/dd.c:957
 bus_for_each_drv+0x220/0x2b4 drivers/base/bus.c:462
 __device_attach+0x26c/0x388 drivers/base/dd.c:1029
 device_initial_probe+0x24/0x34 drivers/base/dd.c:1078
 bus_probe_device+0x178/0x240 drivers/base/bus.c:537
 device_add+0x71c/0xa60 drivers/base/core.c:3692
 usb_new_device+0x7f0/0x1220 drivers/usb/core/hub.c:2694
 hub_port_connect drivers/usb/core/hub.c:5566 [inline]
 hub_port_connect_change drivers/usb/core/hub.c:5706 [inline]
 port_event drivers/usb/core/hub.c:5870 [inline]
 hub_event+0x211c/0x3c78 drivers/usb/core/hub.c:5952
 process_one_work+0x7e8/0x155c kernel/workqueue.c:3238
 process_scheduled_works kernel/workqueue.c:3321 [inline]
 worker_thread+0x958/0xed8 kernel/workqueue.c:3402
 kthread+0x5fc/0x75c kernel/kthread.c:464
 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:844

Freed by task 9:
 kasan_save_stack mm/kasan/common.c:47 [inline]
 kasan_save_track+0x40/0x78 mm/kasan/common.c:68
 kasan_save_free_info+0x58/0x70 mm/kasan/generic.c:576
 poison_slab_object mm/kasan/common.c:247 [inline]
 __kasan_slab_free+0x68/0x88 mm/kasan/common.c:264
 kasan_slab_free include/linux/kasan.h:233 [inline]
 slab_free_hook mm/slub.c:2381 [inline]
 slab_free mm/slub.c:4643 [inline]
 kfree+0x17c/0x474 mm/slub.c:4842
 release_mdev+0x20/0x30 drivers/most/most_usb.c:932
 device_release+0x8c/0x1ac drivers/base/core.c:-1
 kobject_cleanup lib/kobject.c:689 [inline]
 kobject_release lib/kobject.c:720 [inline]
 kref_put include/linux/kref.h:65 [inline]
 kobject_put+0x2b0/0x438 lib/kobject.c:737
 put_device drivers/base/core.c:3800 [inline]
 device_unregister+0x3c/0xcc drivers/base/core.c:3923
 most_deregister_interface+0x3e0/0x42c drivers/most/core.c:1402
 hdm_disconnect+0xdc/0x18c drivers/most/most_usb.c:1123
 usb_unbind_interface+0x244/0x7c8 drivers/usb/core/driver.c:458
 device_remove drivers/base/dd.c:569 [inline]
 __device_release_driver drivers/base/dd.c:1272 [inline]
 device_release_driver_internal+0x3f8/0x658 drivers/base/dd.c:1295
 device_release_driver+0x28/0x38 drivers/base/dd.c:1318
 bus_remove_device+0x310/0x3b0 drivers/base/bus.c:579
 device_del+0x47c/0x808 drivers/base/core.c:3881
 usb_disable_device+0x33c/0x780 drivers/usb/core/message.c:1418
 usb_disconnect+0x284/0x82c drivers/usb/core/hub.c:2344
 hub_port_connect drivers/usb/core/hub.c:5406 [inline]
 hub_port_connect_change drivers/usb/core/hub.c:5706 [inline]
 port_event drivers/usb/core/hub.c:5870 [inline]
 hub_event+0x1688/0x3c78 drivers/usb/core/hub.c:5952
 process_one_work+0x7e8/0x155c kernel/workqueue.c:3238
 process_scheduled_works kernel/workqueue.c:3321 [inline]
 worker_thread+0x958/0xed8 kernel/workqueue.c:3402
 kthread+0x5fc/0x75c kernel/kthread.c:464
 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:844

The buggy address belongs to the object at ffff0000d6c38000
 which belongs to the cache kmalloc-8k of size 8192
The buggy address is located 6312 bytes inside of
 freed 8192-byte region [ffff0000d6c38000, ffff0000d6c3a000)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x116c38
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
anon flags: 0x5ffc00000000040(head|node=0|zone=2|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 05ffc00000000040 ffff0000c0002280 0000000000000000 dead000000000001
raw: 0000000000000000 0000000080020002 00000000f5000000 0000000000000000
head: 05ffc00000000040 ffff0000c0002280 0000000000000000 dead000000000001
head: 0000000000000000 0000000080020002 00000000f5000000 0000000000000000
head: 05ffc00000000003 fffffdffc35b0e01 00000000ffffffff 00000000ffffffff
head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000008
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff0000d6c39780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff0000d6c39800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff0000d6c39880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                  ^
 ffff0000d6c39900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff0000d6c39980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
------------[ cut here ]------------
refcount_t: underflow; use-after-free.
WARNING: CPU: 0 PID: 9 at lib/refcount.c:28 refcount_warn_saturate+0x154/0x1f8 lib/refcount.c:28
Modules linked in:
CPU: 0 UID: 0 PID: 9 Comm: kworker/0:0 Tainted: G    B               6.16.0-rc7-syzkaller-g82af5ea7c611 #0 PREEMPT 
Tainted: [B]=BAD_PAGE
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Workqueue: usb_hub_wq hub_event
pstate: 60400005 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
pc : refcount_warn_saturate+0x154/0x1f8 lib/refcount.c:28
lr : refcount_warn_saturate+0x154/0x1f8 lib/refcount.c:28
sp : ffff800097a67330
x29: ffff800097a67330 x28: ffff0000da60a0b0 x27: 1fffe0001ad87000
x26: 1fffe0001ad87007 x25: dfff800000000000 x24: ffff800092495ab0
x23: 1fffe0001ad870a1 x22: ffff0000d6c3803c x21: 0000000000000000
x20: ffff0000d6c38038 x19: ffff800092c65000 x18: 00000000ffffffff
x17: 0000000000000000 x16: ffff80008ae69508 x15: ffff700011ee0158
x14: 1ffff00011ee0158 x13: 0000000000000004 x12: ffffffffffffffff
x11: ffff700011ee0158 x10: 0000000000ff0100 x9 : 60fc1274729f8600
x8 : 60fc1274729f8600 x7 : 0000000000000001 x6 : 0000000000000001
x5 : ffff800097a66c78 x4 : ffff80008f776bc0 x3 : ffff80008054bdfc
x2 : 0000000000000000 x1 : 0000000100000000 x0 : 0000000000000000
Call trace:
 refcount_warn_saturate+0x154/0x1f8 lib/refcount.c:28 (P)
 __refcount_sub_and_test include/linux/refcount.h:400 [inline]
 __refcount_dec_and_test include/linux/refcount.h:432 [inline]
 refcount_dec_and_test include/linux/refcount.h:450 [inline]
 kref_put include/linux/kref.h:64 [inline]
 kobject_put+0x194/0x438 lib/kobject.c:737
 put_device+0x28/0x40 drivers/base/core.c:3800
 hdm_disconnect+0x174/0x18c drivers/most/most_usb.c:1130
 usb_unbind_interface+0x244/0x7c8 drivers/usb/core/driver.c:458
 device_remove drivers/base/dd.c:569 [inline]
 __device_release_driver drivers/base/dd.c:1272 [inline]
 device_release_driver_internal+0x3f8/0x658 drivers/base/dd.c:1295
 device_release_driver+0x28/0x38 drivers/base/dd.c:1318
 bus_remove_device+0x310/0x3b0 drivers/base/bus.c:579
 device_del+0x47c/0x808 drivers/base/core.c:3881
 usb_disable_device+0x33c/0x780 drivers/usb/core/message.c:1418
 usb_disconnect+0x284/0x82c drivers/usb/core/hub.c:2344
 hub_port_connect drivers/usb/core/hub.c:5406 [inline]
 hub_port_connect_change drivers/usb/core/hub.c:5706 [inline]
 port_event drivers/usb/core/hub.c:5870 [inline]
 hub_event+0x1688/0x3c78 drivers/usb/core/hub.c:5952
 process_one_work+0x7e8/0x155c kernel/workqueue.c:3238
 process_scheduled_works kernel/workqueue.c:3321 [inline]
 worker_thread+0x958/0xed8 kernel/workqueue.c:3402
 kthread+0x5fc/0x75c kernel/kthread.c:464
 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:844
irq event stamp: 44563
hardirqs last  enabled at (44563): [<ffff80008aeff2b4>] __exit_to_kernel_mode arch/arm64/kernel/entry-common.c:86 [inline]
hardirqs last  enabled at (44563): [<ffff80008aeff2b4>] exit_to_kernel_mode+0xc0/0xf0 arch/arm64/kernel/entry-common.c:96
hardirqs last disabled at (44562): [<ffff80008aefc6f4>] __el1_irq arch/arm64/kernel/entry-common.c:650 [inline]
hardirqs last disabled at (44562): [<ffff80008aefc6f4>] el1_interrupt+0x24/0x54 arch/arm64/kernel/entry-common.c:668
softirqs last  enabled at (41128): [<ffff8000803cedfc>] softirq_handle_end kernel/softirq.c:425 [inline]
softirqs last  enabled at (41128): [<ffff8000803cedfc>] handle_softirqs+0xaf8/0xc88 kernel/softirq.c:607
softirqs last disabled at (41105): [<ffff800080020efc>] __do_softirq+0x14/0x20 kernel/softirq.c:613
---[ end trace 0000000000000000 ]---
usb 1-1: new high-speed USB device number 4 using dummy_hcd
usb 1-1: config 0 has an invalid interface number: 230 but max is 0
usb 1-1: config 0 has no interface number 0
usb 1-1: config 0 interface 230 altsetting 0 endpoint 0x4 has invalid maxpacket 1024, setting to 64
usb 1-1: New USB device found, idVendor=0424, idProduct=c001, bcdDevice=7f.ee
usb 1-1: New USB device strings: Mfr=0, Product=0, SerialNumber=0
usb 1-1: config 0 descriptor??

final repro crashed as (corrupted=false):
usb 1-1: config 0 descriptor??
usb 1-1: USB disconnect, device number 2
==================================================================
BUG: KASAN: slab-use-after-free in hdm_disconnect+0xf4/0x18c drivers/most/most_usb.c:1125
Read of size 8 at addr ffff0000d6c398a8 by task kworker/0:0/9

CPU: 0 UID: 0 PID: 9 Comm: kworker/0:0 Not tainted 6.16.0-rc7-syzkaller-g82af5ea7c611 #0 PREEMPT 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Workqueue: usb_hub_wq hub_event
Call trace:
 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:499 (C)
 __dump_stack+0x30/0x40 lib/dump_stack.c:94
 dump_stack_lvl+0xd8/0x12c lib/dump_stack.c:120
 print_address_description+0xa8/0x220 mm/kasan/report.c:378
 print_report+0x68/0x84 mm/kasan/report.c:480
 kasan_report+0xb0/0x110 mm/kasan/report.c:593
 __asan_report_load8_noabort+0x20/0x2c mm/kasan/report_generic.c:381
 hdm_disconnect+0xf4/0x18c drivers/most/most_usb.c:1125
 usb_unbind_interface+0x244/0x7c8 drivers/usb/core/driver.c:458
 device_remove drivers/base/dd.c:569 [inline]
 __device_release_driver drivers/base/dd.c:1272 [inline]
 device_release_driver_internal+0x3f8/0x658 drivers/base/dd.c:1295
 device_release_driver+0x28/0x38 drivers/base/dd.c:1318
 bus_remove_device+0x310/0x3b0 drivers/base/bus.c:579
 device_del+0x47c/0x808 drivers/base/core.c:3881
 usb_disable_device+0x33c/0x780 drivers/usb/core/message.c:1418
 usb_disconnect+0x284/0x82c drivers/usb/core/hub.c:2344
 hub_port_connect drivers/usb/core/hub.c:5406 [inline]
 hub_port_connect_change drivers/usb/core/hub.c:5706 [inline]
 port_event drivers/usb/core/hub.c:5870 [inline]
 hub_event+0x1688/0x3c78 drivers/usb/core/hub.c:5952
 process_one_work+0x7e8/0x155c kernel/workqueue.c:3238
 process_scheduled_works kernel/workqueue.c:3321 [inline]
 worker_thread+0x958/0xed8 kernel/workqueue.c:3402
 kthread+0x5fc/0x75c kernel/kthread.c:464
 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:844

Allocated by task 9:
 kasan_save_stack mm/kasan/common.c:47 [inline]
 kasan_save_track+0x40/0x78 mm/kasan/common.c:68
 kasan_save_alloc_info+0x44/0x54 mm/kasan/generic.c:562
 poison_kmalloc_redzone mm/kasan/common.c:377 [inline]
 __kasan_kmalloc+0x9c/0xb4 mm/kasan/common.c:394
 kasan_kmalloc include/linux/kasan.h:260 [inline]
 __kmalloc_cache_noprof+0x2a4/0x3fc mm/slub.c:4359
 kmalloc_noprof include/linux/slab.h:905 [inline]
 kzalloc_noprof include/linux/slab.h:1039 [inline]
 hdm_probe+0x9c/0x1044 drivers/most/most_usb.c:959
 usb_probe_interface+0x584/0xa44 drivers/usb/core/driver.c:396
 call_driver_probe drivers/base/dd.c:-1 [inline]
 really_probe+0x394/0x910 drivers/base/dd.c:657
 __driver_probe_device+0x180/0x2d4 drivers/base/dd.c:799
 driver_probe_device+0x78/0x330 drivers/base/dd.c:829
 __device_attach_driver+0x290/0x4e0 drivers/base/dd.c:957
 bus_for_each_drv+0x220/0x2b4 drivers/base/bus.c:462
 __device_attach+0x26c/0x388 drivers/base/dd.c:1029
 device_initial_probe+0x24/0x34 drivers/base/dd.c:1078
 bus_probe_device+0x178/0x240 drivers/base/bus.c:537
 device_add+0x71c/0xa60 drivers/base/core.c:3692
 usb_set_configuration+0x1640/0x1bac drivers/usb/core/message.c:2210
 usb_generic_driver_probe+0x8c/0x144 drivers/usb/core/generic.c:250
 usb_probe_device+0x1a4/0x348 drivers/usb/core/driver.c:291
 call_driver_probe drivers/base/dd.c:-1 [inline]
 really_probe+0x394/0x910 drivers/base/dd.c:657
 __driver_probe_device+0x180/0x2d4 drivers/base/dd.c:799
 driver_probe_device+0x78/0x330 drivers/base/dd.c:829
 __device_attach_driver+0x290/0x4e0 drivers/base/dd.c:957
 bus_for_each_drv+0x220/0x2b4 drivers/base/bus.c:462
 __device_attach+0x26c/0x388 drivers/base/dd.c:1029
 device_initial_probe+0x24/0x34 drivers/base/dd.c:1078
 bus_probe_device+0x178/0x240 drivers/base/bus.c:537
 device_add+0x71c/0xa60 drivers/base/core.c:3692
 usb_new_device+0x7f0/0x1220 drivers/usb/core/hub.c:2694
 hub_port_connect drivers/usb/core/hub.c:5566 [inline]
 hub_port_connect_change drivers/usb/core/hub.c:5706 [inline]
 port_event drivers/usb/core/hub.c:5870 [inline]
 hub_event+0x211c/0x3c78 drivers/usb/core/hub.c:5952
 process_one_work+0x7e8/0x155c kernel/workqueue.c:3238
 process_scheduled_works kernel/workqueue.c:3321 [inline]
 worker_thread+0x958/0xed8 kernel/workqueue.c:3402
 kthread+0x5fc/0x75c kernel/kthread.c:464
 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:844

Freed by task 9:
 kasan_save_stack mm/kasan/common.c:47 [inline]
 kasan_save_track+0x40/0x78 mm/kasan/common.c:68
 kasan_save_free_info+0x58/0x70 mm/kasan/generic.c:576
 poison_slab_object mm/kasan/common.c:247 [inline]
 __kasan_slab_free+0x68/0x88 mm/kasan/common.c:264
 kasan_slab_free include/linux/kasan.h:233 [inline]
 slab_free_hook mm/slub.c:2381 [inline]
 slab_free mm/slub.c:4643 [inline]
 kfree+0x17c/0x474 mm/slub.c:4842
 release_mdev+0x20/0x30 drivers/most/most_usb.c:932
 device_release+0x8c/0x1ac drivers/base/core.c:-1
 kobject_cleanup lib/kobject.c:689 [inline]
 kobject_release lib/kobject.c:720 [inline]
 kref_put include/linux/kref.h:65 [inline]
 kobject_put+0x2b0/0x438 lib/kobject.c:737
 put_device drivers/base/core.c:3800 [inline]
 device_unregister+0x3c/0xcc drivers/base/core.c:3923
 most_deregister_interface+0x3e0/0x42c drivers/most/core.c:1402
 hdm_disconnect+0xdc/0x18c drivers/most/most_usb.c:1123
 usb_unbind_interface+0x244/0x7c8 drivers/usb/core/driver.c:458
 device_remove drivers/base/dd.c:569 [inline]
 __device_release_driver drivers/base/dd.c:1272 [inline]
 device_release_driver_internal+0x3f8/0x658 drivers/base/dd.c:1295
 device_release_driver+0x28/0x38 drivers/base/dd.c:1318
 bus_remove_device+0x310/0x3b0 drivers/base/bus.c:579
 device_del+0x47c/0x808 drivers/base/core.c:3881
 usb_disable_device+0x33c/0x780 drivers/usb/core/message.c:1418
 usb_disconnect+0x284/0x82c drivers/usb/core/hub.c:2344
 hub_port_connect drivers/usb/core/hub.c:5406 [inline]
 hub_port_connect_change drivers/usb/core/hub.c:5706 [inline]
 port_event drivers/usb/core/hub.c:5870 [inline]
 hub_event+0x1688/0x3c78 drivers/usb/core/hub.c:5952
 process_one_work+0x7e8/0x155c kernel/workqueue.c:3238
 process_scheduled_works kernel/workqueue.c:3321 [inline]
 worker_thread+0x958/0xed8 kernel/workqueue.c:3402
 kthread+0x5fc/0x75c kernel/kthread.c:464
 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:844

The buggy address belongs to the object at ffff0000d6c38000
 which belongs to the cache kmalloc-8k of size 8192
The buggy address is located 6312 bytes inside of
 freed 8192-byte region [ffff0000d6c38000, ffff0000d6c3a000)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x116c38
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
anon flags: 0x5ffc00000000040(head|node=0|zone=2|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 05ffc00000000040 ffff0000c0002280 0000000000000000 dead000000000001
raw: 0000000000000000 0000000080020002 00000000f5000000 0000000000000000
head: 05ffc00000000040 ffff0000c0002280 0000000000000000 dead000000000001
head: 0000000000000000 0000000080020002 00000000f5000000 0000000000000000
head: 05ffc00000000003 fffffdffc35b0e01 00000000ffffffff 00000000ffffffff
head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000008
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff0000d6c39780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff0000d6c39800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff0000d6c39880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                  ^
 ffff0000d6c39900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff0000d6c39980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
------------[ cut here ]------------
refcount_t: underflow; use-after-free.
WARNING: CPU: 0 PID: 9 at lib/refcount.c:28 refcount_warn_saturate+0x154/0x1f8 lib/refcount.c:28
Modules linked in:
CPU: 0 UID: 0 PID: 9 Comm: kworker/0:0 Tainted: G    B               6.16.0-rc7-syzkaller-g82af5ea7c611 #0 PREEMPT 
Tainted: [B]=BAD_PAGE
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Workqueue: usb_hub_wq hub_event
pstate: 60400005 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
pc : refcount_warn_saturate+0x154/0x1f8 lib/refcount.c:28
lr : refcount_warn_saturate+0x154/0x1f8 lib/refcount.c:28
sp : ffff800097a67330
x29: ffff800097a67330 x28: ffff0000da60a0b0 x27: 1fffe0001ad87000
x26: 1fffe0001ad87007 x25: dfff800000000000 x24: ffff800092495ab0
x23: 1fffe0001ad870a1 x22: ffff0000d6c3803c x21: 0000000000000000
x20: ffff0000d6c38038 x19: ffff800092c65000 x18: 00000000ffffffff
x17: 0000000000000000 x16: ffff80008ae69508 x15: ffff700011ee0158
x14: 1ffff00011ee0158 x13: 0000000000000004 x12: ffffffffffffffff
x11: ffff700011ee0158 x10: 0000000000ff0100 x9 : 60fc1274729f8600
x8 : 60fc1274729f8600 x7 : 0000000000000001 x6 : 0000000000000001
x5 : ffff800097a66c78 x4 : ffff80008f776bc0 x3 : ffff80008054bdfc
x2 : 0000000000000000 x1 : 0000000100000000 x0 : 0000000000000000
Call trace:
 refcount_warn_saturate+0x154/0x1f8 lib/refcount.c:28 (P)
 __refcount_sub_and_test include/linux/refcount.h:400 [inline]
 __refcount_dec_and_test include/linux/refcount.h:432 [inline]
 refcount_dec_and_test include/linux/refcount.h:450 [inline]
 kref_put include/linux/kref.h:64 [inline]
 kobject_put+0x194/0x438 lib/kobject.c:737
 put_device+0x28/0x40 drivers/base/core.c:3800
 hdm_disconnect+0x174/0x18c drivers/most/most_usb.c:1130
 usb_unbind_interface+0x244/0x7c8 drivers/usb/core/driver.c:458
 device_remove drivers/base/dd.c:569 [inline]
 __device_release_driver drivers/base/dd.c:1272 [inline]
 device_release_driver_internal+0x3f8/0x658 drivers/base/dd.c:1295
 device_release_driver+0x28/0x38 drivers/base/dd.c:1318
 bus_remove_device+0x310/0x3b0 drivers/base/bus.c:579
 device_del+0x47c/0x808 drivers/base/core.c:3881
 usb_disable_device+0x33c/0x780 drivers/usb/core/message.c:1418
 usb_disconnect+0x284/0x82c drivers/usb/core/hub.c:2344
 hub_port_connect drivers/usb/core/hub.c:5406 [inline]
 hub_port_connect_change drivers/usb/core/hub.c:5706 [inline]
 port_event drivers/usb/core/hub.c:5870 [inline]
 hub_event+0x1688/0x3c78 drivers/usb/core/hub.c:5952
 process_one_work+0x7e8/0x155c kernel/workqueue.c:3238
 process_scheduled_works kernel/workqueue.c:3321 [inline]
 worker_thread+0x958/0xed8 kernel/workqueue.c:3402
 kthread+0x5fc/0x75c kernel/kthread.c:464
 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:844
irq event stamp: 44563
hardirqs last  enabled at (44563): [<ffff80008aeff2b4>] __exit_to_kernel_mode arch/arm64/kernel/entry-common.c:86 [inline]
hardirqs last  enabled at (44563): [<ffff80008aeff2b4>] exit_to_kernel_mode+0xc0/0xf0 arch/arm64/kernel/entry-common.c:96
hardirqs last disabled at (44562): [<ffff80008aefc6f4>] __el1_irq arch/arm64/kernel/entry-common.c:650 [inline]
hardirqs last disabled at (44562): [<ffff80008aefc6f4>] el1_interrupt+0x24/0x54 arch/arm64/kernel/entry-common.c:668
softirqs last  enabled at (41128): [<ffff8000803cedfc>] softirq_handle_end kernel/softirq.c:425 [inline]
softirqs last  enabled at (41128): [<ffff8000803cedfc>] handle_softirqs+0xaf8/0xc88 kernel/softirq.c:607
softirqs last disabled at (41105): [<ffff800080020efc>] __do_softirq+0x14/0x20 kernel/softirq.c:613
---[ end trace 0000000000000000 ]---
usb 1-1: new high-speed USB device number 4 using dummy_hcd
usb 1-1: config 0 has an invalid interface number: 230 but max is 0
usb 1-1: config 0 has no interface number 0
usb 1-1: config 0 interface 230 altsetting 0 endpoint 0x4 has invalid maxpacket 1024, setting to 64
usb 1-1: New USB device found, idVendor=0424, idProduct=c001, bcdDevice=7f.ee
usb 1-1: New USB device strings: Mfr=0, Product=0, SerialNumber=0
usb 1-1: config 0 descriptor??