KASAN: slab-use-after-free Read in __dynamic_dev_dbg

Status: upstream: reported C repro on 2026/09/16 15:53
Subsystems: media
[Documentation on labels]
Reported-by: syzbot+9bfac891bdd42eb708fc@syzkaller.appspotmail.com
First crash: 1d14h, last: 2h43m
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ID Workflow Result Correct Bug Created Started Finished Revision
07258edd assessment-security 💥 KASAN: slab-use-after-free Read in __dynamic_dev_dbg 2026/09/16 00:44 2026/09/16 00:44 2026/09/16 00:44 2daa4bb5
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[syzbot] [media?] KASAN: slab-use-after-free Read in __dynamic_dev_dbg 0 (1) 2026/09/16 15:53

Sample crash report:
==================================================================
BUG: KASAN: slab-use-after-free in dev_name include/linux/device.h:934 [inline]
BUG: KASAN: slab-use-after-free in __dynamic_dev_dbg+0x2fc/0x310 lib/dynamic_debug.c:904
Read of size 8 at addr ffff88804cba20c8 by task syz.0.17/6046

CPU: 2 UID: 0 PID: 6046 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:378 [inline]
 print_report+0x13d/0x4b0 mm/kasan/report.c:482
 kasan_report+0xdf/0x1c0 mm/kasan/report.c:595
 dev_name include/linux/device.h:934 [inline]
 __dynamic_dev_dbg+0x2fc/0x310 lib/dynamic_debug.c:904
 display_close+0x103/0x150 drivers/media/rc/imon.c:580
 __fput+0x3ff/0xb50 fs/file_table.c:512
 task_work_run+0x150/0x240 kernel/task_work.c:233
 exit_task_work include/linux/task_work.h:40 [inline]
 do_exit+0x951/0x2ae0 kernel/exit.c:1011
 do_group_exit+0xd5/0x2a0 kernel/exit.c:1154
 get_signal+0x1ec7/0x21e0 kernel/signal.c:3051
 arch_do_signal_or_restart+0x91/0x7a0 arch/x86/kernel/signal.c:337
 __exit_to_user_mode_loop kernel/entry/common.c:66 [inline]
 exit_to_user_mode_loop+0x139/0x700 kernel/entry/common.c:101
 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:207 [inline]
 syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:230 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:336 [inline]
 do_int80_emulation+0x555/0x650 arch/x86/entry/syscall_32.c:169
 asm_int80_emulation+0x1a/0x20 arch/x86/include/asm/idtentry.h:598
RIP: 0023:0xf71575ab
Code: Unable to access opcode bytes at 0xf7157581.
RSP: 002b:00000000ffb6690c EFLAGS: 00000246
 ORIG_RAX: 000000000000010b
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 00000000ffb669a4 RSI: 00000000ffb6699c RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000202 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
 </TASK>

Allocated by task 30:
 kasan_save_stack+0x30/0x50 mm/kasan/common.c:57
 kasan_save_track+0x14/0x30 mm/kasan/common.c:78
 poison_kmalloc_redzone mm/kasan/common.c:398 [inline]
 __kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:415
 kasan_kmalloc include/linux/kasan.h:263 [inline]
 __kmalloc_cache_noprof+0x2f8/0x6d0 mm/slub.c:5563
 _kmalloc_noprof include/linux/slab.h:991 [inline]
 _kzalloc_noprof include/linux/slab.h:1312 [inline]
 usb_set_configuration+0x10cb/0x1c60 drivers/usb/core/message.c:2096
 usb_generic_driver_probe+0xa1/0xe0 drivers/usb/core/generic.c:250
 usb_probe_device+0xef/0x400 drivers/usb/core/driver.c:293
 call_driver_probe drivers/base/dd.c:628 [inline]
 really_probe+0x241/0xa60 drivers/base/dd.c:706
 __driver_probe_device+0x210/0x460 drivers/base/dd.c:868
 driver_probe_device+0x4a/0x140 drivers/base/dd.c:898
 __device_attach_driver+0x1df/0x320 drivers/base/dd.c:1026
 bus_for_each_drv+0x159/0x1e0 drivers/base/bus.c:500
 __device_attach+0x1e4/0x4d0 drivers/base/dd.c:1098
 device_initial_probe+0xaf/0xd0 drivers/base/dd.c:1153
 bus_probe_device+0x64/0x160 drivers/base/bus.c:620
 device_add+0x121d/0x1970 drivers/base/core.c:3776
 usb_new_device.part.0+0xcc2/0x1686 drivers/usb/core/hub.c:2708
 usb_new_device include/linux/workqueue.h:715 [inline]
 hub_port_connect drivers/usb/core/hub.c:5580 [inline]
 hub_port_connect_change drivers/usb/core/hub.c:5720 [inline]
 port_event drivers/usb/core/hub.c:5884 [inline]
 hub_event.cold+0x1e3/0xe90 drivers/usb/core/hub.c:5966
 process_one_work+0xac7/0x1b10 kernel/workqueue.c:3396
 process_scheduled_works kernel/workqueue.c:3479 [inline]
 worker_thread+0x5ef/0xe50 kernel/workqueue.c:3560
 kthread+0x373/0x450 kernel/kthread.c:436
 ret_from_fork+0x730/0xd60 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

Freed by task 5842:
 kasan_save_stack+0x30/0x50 mm/kasan/common.c:57
 kasan_save_track+0x14/0x30 mm/kasan/common.c:78
 kasan_save_free_info+0x3b/0x70 mm/kasan/generic.c:584
 poison_slab_object mm/kasan/common.c:253 [inline]
 __kasan_slab_free+0x5f/0x80 mm/kasan/common.c:285
 kasan_slab_free include/linux/kasan.h:235 [inline]
 slab_free_hook mm/slub.c:2748 [inline]
 slab_free mm/slub.c:6499 [inline]
 kfree+0x22b/0x6d0 mm/slub.c:6792
 device_release+0xd2/0x270 drivers/base/core.c:2640
 kobject_cleanup lib/kobject.c:689 [inline]
 kobject_release lib/kobject.c:720 [inline]
 kref_put include/linux/kref.h:65 [inline]
 kobject_put+0x1f7/0x640 lib/kobject.c:737
 put_device+0x1f/0x30 drivers/base/core.c:3884
 usb_disable_device+0x44a/0x810 drivers/usb/core/message.c:1485
 usb_disconnect+0x2e2/0x9a0 drivers/usb/core/hub.c:2350
 hub_port_connect drivers/usb/core/hub.c:5420 [inline]
 hub_port_connect_change drivers/usb/core/hub.c:5720 [inline]
 port_event drivers/usb/core/hub.c:5884 [inline]
 hub_event+0x1bb1/0x4420 drivers/usb/core/hub.c:5966
 process_one_work+0xac7/0x1b10 kernel/workqueue.c:3396
 process_scheduled_works kernel/workqueue.c:3479 [inline]
 worker_thread+0x5ef/0xe50 kernel/workqueue.c:3560
 kthread+0x373/0x450 kernel/kthread.c:436
 ret_from_fork+0x730/0xd60 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 ffff88804cba2000
 which belongs to the cache kmalloc-2k of size 2048
The buggy address is located 200 bytes inside of
 freed 2048-byte region [ffff88804cba2000, ffff88804cba2800)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x4cba0
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0x4fff00000000040(head|node=1|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 04fff00000000040 ffff88801c042f00 dead000000000100 dead000000000122
raw: 0000000000000000 0000000000080008 00000000f5000000 0000000000000000
head: 04fff00000000040 ffff88801c042f00 dead000000000100 dead000000000122
head: 0000000000000000 0000000000080008 00000000f5000000 0000000000000000
head: 04fff00000000003 fffffffffffffe01 00000000ffffffff 00000000ffffffff
head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000008
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 3, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 5859, tgid 5859 (kworker/1:4), ts 49377453462
 set_page_owner include/linux/page_owner.h:33 [inline]
 post_alloc_hook+0xfd/0x120 mm/page_alloc.c:1871
 prep_new_page mm/page_alloc.c:1879 [inline]
 get_page_from_freelist+0x110d/0x35d0 mm/page_alloc.c:3943
 __alloc_frozen_pages_noprof+0x2eb/0x3300 mm/page_alloc.c:5436
 alloc_slab_page mm/slub.c:3347 [inline]
 allocate_slab mm/slub.c:3462 [inline]
 new_slab+0xa9/0x6e0 mm/slub.c:3513
 refill_objects+0xe3/0x410 mm/slub.c:7410
 refill_sheaf mm/slub.c:2885 [inline]
 __pcs_replace_empty_main+0x35e/0x650 mm/slub.c:4774
 alloc_from_pcs mm/slub.c:4850 [inline]
 slab_alloc_node mm/slub.c:4984 [inline]
 __do_kmalloc_node mm/slub.c:5413 [inline]
 __kmalloc_node_track_caller_noprof+0x6a8/0x870 mm/slub.c:5545
 kmalloc_reserve+0xe8/0x350 net/core/skbuff.c:637
 __alloc_skb+0x185/0x710 net/core/skbuff.c:715
 alloc_skb include/linux/skbuff.h:1384 [inline]
 mld_newpack.isra.0+0x18e/0xa20 net/ipv6/mcast.c:1810
 add_grhead+0x299/0x340 net/ipv6/mcast.c:1921
 add_grec+0x1389/0x1930 net/ipv6/mcast.c:2060
 mld_send_cr net/ipv6/mcast.c:2185 [inline]
 mld_ifc_work+0x3c5/0xc10 net/ipv6/mcast.c:2739
 process_one_work+0xac7/0x1b10 kernel/workqueue.c:3396
 process_scheduled_works kernel/workqueue.c:3479 [inline]
 worker_thread+0x5ef/0xe50 kernel/workqueue.c:3560
 kthread+0x373/0x450 kernel/kthread.c:436
page last free pid 5161 tgid 5161 ts 12784202840 stack trace:
 reset_page_owner include/linux/page_owner.h:26 [inline]
 __free_pages_prepare mm/page_alloc.c:1418 [inline]
 __free_frozen_pages+0x79f/0x10f0 mm/page_alloc.c:2962
 qlink_free mm/kasan/quarantine.c:163 [inline]
 qlist_free_all+0x47/0xf0 mm/kasan/quarantine.c:179
 kasan_quarantine_reduce+0x1a0/0x1f0 mm/kasan/quarantine.c:286
 __kasan_slab_alloc+0x69/0x90 mm/kasan/common.c:350
 kasan_slab_alloc include/linux/kasan.h:253 [inline]
 slab_post_alloc_hook mm/slub.c:4683 [inline]
 slab_alloc_node mm/slub.c:4996 [inline]
 kmem_cache_alloc_noprof+0x269/0x6a0 mm/slub.c:5010
 alloc_filename fs/namei.c:147 [inline]
 do_getname+0x35/0x390 fs/namei.c:187
 getname include/linux/fs.h:2557 [inline]
 getname_maybe_null include/linux/fs.h:2564 [inline]
 class_filename_maybe_null_constructor include/linux/fs.h:2588 [inline]
 vfs_fstatat+0xd0/0xe0 fs/stat.c:368
 __do_sys_newfstatat+0x9d/0x120 fs/stat.c:538
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x121/0x770 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
 ffff88804cba1f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88804cba2000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88804cba2080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                              ^
 ffff88804cba2100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88804cba2180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

Crashes (23):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/09/15 22:44 upstream 50d05c7c76c9 f41e228a .config console log report syz / log C [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream-386 KASAN: slab-use-after-free Read in __dynamic_dev_dbg
2026/09/16 13:01 upstream 9b87fdc9af2f 12a0a44a .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-badwrites-root KASAN: slab-use-after-free Read in __dynamic_dev_dbg
2026/09/16 04:34 upstream 9b87fdc9af2f 12a0a44a .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root KASAN: slab-use-after-free Read in __dynamic_dev_dbg
2026/09/15 20:51 upstream f6e7b42bf05b f41e228a .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream KASAN: slab-use-after-free Read in __dynamic_dev_dbg
2026/09/15 15:11 upstream 587858367581 f41e228a .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream KASAN: slab-use-after-free Read in __dynamic_dev_dbg
2026/09/15 13:58 upstream 587858367581 f41e228a .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream KASAN: slab-use-after-free Read in __dynamic_dev_dbg
2026/09/15 09:27 upstream 587858367581 81a27d1a .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-use-after-free Read in __dynamic_dev_dbg
2026/09/15 07:01 upstream 587858367581 81a27d1a .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-use-after-free Read in __dynamic_dev_dbg
2026/09/16 07:31 upstream 50d05c7c76c9 12a0a44a .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream-386 KASAN: slab-use-after-free Read in __dynamic_dev_dbg
2026/09/16 06:39 upstream 50d05c7c76c9 12a0a44a .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream-386 KASAN: slab-use-after-free Read in __dynamic_dev_dbg
2026/09/16 01:16 upstream 50d05c7c76c9 12a0a44a .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream-386 KASAN: slab-use-after-free Read in __dynamic_dev_dbg
2026/09/15 23:02 upstream 50d05c7c76c9 f41e228a .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream-386 KASAN: slab-use-after-free Read in __dynamic_dev_dbg
2026/09/15 23:00 upstream 50d05c7c76c9 f41e228a .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream-386 KASAN: slab-use-after-free Read in __dynamic_dev_dbg
2026/09/15 19:15 upstream 50d05c7c76c9 f41e228a .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream-386 KASAN: slab-use-after-free Read in __dynamic_dev_dbg
2026/09/15 17:27 upstream 50d05c7c76c9 f41e228a .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream-386 KASAN: slab-use-after-free Read in __dynamic_dev_dbg
2026/09/16 18:32 linux-next 9d80aa4617b3 95928915 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-rust-kasan-gce KASAN: slab-use-after-free Read in __dynamic_dev_dbg
2026/09/16 18:32 linux-next 9d80aa4617b3 95928915 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-rust-kasan-gce KASAN: slab-use-after-free Read in __dynamic_dev_dbg
2026/09/16 17:21 linux-next 9d80aa4617b3 95928915 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-rust-kasan-gce KASAN: slab-use-after-free Read in __dynamic_dev_dbg
2026/09/16 17:20 linux-next 9d80aa4617b3 95928915 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-rust-kasan-gce KASAN: slab-use-after-free Read in __dynamic_dev_dbg
2026/09/16 05:57 linux-next 9d80aa4617b3 12a0a44a .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-rust-kasan-gce KASAN: slab-use-after-free Read in __dynamic_dev_dbg
2026/09/16 05:29 linux-next 9d80aa4617b3 12a0a44a .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-rust-kasan-gce KASAN: slab-use-after-free Read in __dynamic_dev_dbg
2026/09/15 18:55 linux-next 9d80aa4617b3 81a27d1a .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-rust-kasan-gce KASAN: slab-use-after-free Read in __dynamic_dev_dbg
2026/09/15 19:56 upstream 587858367581 81a27d1a .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root general protection fault in __dynamic_dev_dbg
* Struck through repros no longer work on HEAD.