[syzbot] [media?] KASAN: slab-use-after-free Read in em28xx_unregister_media_device

[syzbot] [media?] KASAN: slab-use-after-free Read in em28xx_unregister_media_device

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    5ac87cd859ec Merge 6.19-rc6 usb-next
git tree:       https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git usb-testing
console output: https://syzkaller.appspot.com/x/log.txt?x=140e73fa580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=a04e768f944f1aa0
dashboard link: https://syzkaller.appspot.com/bug?extid=07b93bb3189febcab189
compiler:       gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/b927a84e0088/disk-5ac87cd8.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/b8131bd9dbee/vmlinux-5ac87cd8.xz
kernel image: https://storage.googleapis.com/syzbot-assets/24fc40a81925/bzImage-5ac87cd8.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+07b93bb3189febcab189@syzkaller.appspotmail.com

em28xx 8-1:0.132: Closing input extension
==================================================================
BUG: KASAN: slab-use-after-free in media_device_unregister drivers/media/mc/mc-device.c:804 [inline]
BUG: KASAN: slab-use-after-free in media_device_unregister+0x565/0x5e0 drivers/media/mc/mc-device.c:782
Read of size 8 at addr ffff88813572c210 by task kworker/1:6/5730

CPU: 1 UID: 0 PID: 5730 Comm: kworker/1:6 Not tainted syzkaller #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Workqueue: usb_hub_wq hub_event
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+0x156/0x4c9 mm/kasan/report.c:482
 kasan_report+0xdf/0x1a0 mm/kasan/report.c:595
 media_device_unregister drivers/media/mc/mc-device.c:804 [inline]
 media_device_unregister+0x565/0x5e0 drivers/media/mc/mc-device.c:782
 em28xx_unregister_media_device+0x4e/0xe0 drivers/media/usb/em28xx/em28xx-cards.c:3511
 em28xx_release_resources+0x79/0x1b0 drivers/media/usb/em28xx/em28xx-cards.c:3532
 em28xx_usb_disconnect.cold+0x17d/0x253 drivers/media/usb/em28xx/em28xx-cards.c:4201
 usb_unbind_interface+0x1dd/0x9e0 drivers/usb/core/driver.c:458
 device_remove drivers/base/dd.c:571 [inline]
 device_remove+0x12a/0x180 drivers/base/dd.c:563
 __device_release_driver drivers/base/dd.c:1282 [inline]
 device_release_driver_internal+0x42e/0x600 drivers/base/dd.c:1305
 bus_remove_device+0x22f/0x440 drivers/base/bus.c:616
 device_del+0x376/0x9b0 drivers/base/core.c:3878
 usb_disable_device+0x367/0x810 drivers/usb/core/message.c:1418
 usb_disconnect+0x2e2/0x9a0 drivers/usb/core/hub.c:2345
 hub_port_connect drivers/usb/core/hub.c:5407 [inline]
 hub_port_connect_change drivers/usb/core/hub.c:5707 [inline]
 port_event drivers/usb/core/hub.c:5871 [inline]
 hub_event+0x1d0c/0x4af0 drivers/usb/core/hub.c:5953
 process_one_work+0x9c2/0x1840 kernel/workqueue.c:3257
 process_scheduled_works kernel/workqueue.c:3340 [inline]
 worker_thread+0x5da/0xe40 kernel/workqueue.c:3421
 kthread+0x3b3/0x730 kernel/kthread.c:463
 ret_from_fork+0x6c3/0xa20 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246
 </TASK>

Allocated by task 11958:
 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+0x8f/0xa0 mm/kasan/common.c:415
 kmalloc_noprof include/linux/slab.h:957 [inline]
 kzalloc_noprof include/linux/slab.h:1094 [inline]
 em28xx_v4l2_init.cold+0x94/0x3503 drivers/media/usb/em28xx/em28xx-video.c:2532
 em28xx_init_extension+0x13a/0x200 drivers/media/usb/em28xx/em28xx-core.c:1117
 request_module_async+0x61/0x80 drivers/media/usb/em28xx/em28xx-cards.c:3457
 process_one_work+0x9c2/0x1840 kernel/workqueue.c:3257
 process_scheduled_works kernel/workqueue.c:3340 [inline]
 worker_thread+0x5da/0xe40 kernel/workqueue.c:3421
 kthread+0x3b3/0x730 kernel/kthread.c:463
 ret_from_fork+0x6c3/0xa20 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246

Freed by task 11958:
 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+0x43/0x70 mm/kasan/common.c:285
 kasan_slab_free include/linux/kasan.h:235 [inline]
 slab_free_hook mm/slub.c:2540 [inline]
 slab_free mm/slub.c:6670 [inline]
 kfree+0x1ad/0x630 mm/slub.c:6878
 kref_put.isra.0+0x56/0x90 include/linux/kref.h:65
 em28xx_v4l2_init.cold+0x280/0x3503 drivers/media/usb/em28xx/em28xx-video.c:2901
 em28xx_init_extension+0x13a/0x200 drivers/media/usb/em28xx/em28xx-core.c:1117
 request_module_async+0x61/0x80 drivers/media/usb/em28xx/em28xx-cards.c:3457
 process_one_work+0x9c2/0x1840 kernel/workqueue.c:3257
 process_scheduled_works kernel/workqueue.c:3340 [inline]
 worker_thread+0x5da/0xe40 kernel/workqueue.c:3421
 kthread+0x3b3/0x730 kernel/kthread.c:463
 ret_from_fork+0x6c3/0xa20 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246

The buggy address belongs to the object at ffff88813572c000
 which belongs to the cache kmalloc-8k of size 8192
The buggy address is located 528 bytes inside of
 freed 8192-byte region [ffff88813572c000, ffff88813572e000)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x135728
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0x200000000000040(head|node=0|zone=2)
page_type: f5(slab)
raw: 0200000000000040 ffff888100042280 ffffea00046dc600 dead000000000002
raw: 0000000000000000 0000000080020002 00000000f5000000 0000000000000000
head: 0200000000000040 ffff888100042280 ffffea00046dc600 dead000000000002
head: 0000000000000000 0000000080020002 00000000f5000000 0000000000000000
head: 0200000000000003 ffffea0004d5ca01 00000000ffffffff 00000000ffffffff
head: 0000000000000000 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 1122, tgid 1122 (kworker/1:2), ts 1154723928347, free_ts 1154474178179
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x1e1/0x250 mm/page_alloc.c:1884
 prep_new_page mm/page_alloc.c:1892 [inline]
 get_page_from_freelist+0xd57/0x3b20 mm/page_alloc.c:3945
 __alloc_frozen_pages_noprof+0x269/0x2230 mm/page_alloc.c:5240
 alloc_pages_mpol+0xe8/0x410 mm/mempolicy.c:2486
 alloc_slab_page mm/slub.c:3075 [inline]
 allocate_slab mm/slub.c:3248 [inline]
 new_slab+0x2c4/0x440 mm/slub.c:3302
 ___slab_alloc+0xda3/0x1ca0 mm/slub.c:4656
 __slab_alloc.isra.0+0x63/0x110 mm/slub.c:4779
 __slab_alloc_node mm/slub.c:4855 [inline]
 slab_alloc_node mm/slub.c:5251 [inline]
 __do_kmalloc_node mm/slub.c:5656 [inline]
 __kmalloc_noprof+0x5c3/0x990 mm/slub.c:5669
 kmalloc_noprof include/linux/slab.h:961 [inline]
 hcd_buffer_alloc+0x1f5/0x290 drivers/usb/core/buffer.c:134
 usb_alloc_coherent+0x5f/0xa0 drivers/usb/core/usb.c:1010
 hdpvr_alloc_buffers+0x12e/0x650 drivers/media/usb/hdpvr/hdpvr-video.c:162
 hdpvr_probe.cold+0x929/0x12fe drivers/media/usb/hdpvr/hdpvr-core.c:350
 usb_probe_interface+0x303/0x8f0 drivers/usb/core/driver.c:396
 call_driver_probe drivers/base/dd.c:581 [inline]
 really_probe+0x241/0xa60 drivers/base/dd.c:659
 __driver_probe_device+0x1de/0x400 drivers/base/dd.c:801
 driver_probe_device+0x4c/0x1b0 drivers/base/dd.c:831
page last free pid 2860 tgid 2860 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1433 [inline]
 __free_frozen_pages+0x7d1/0x1010 mm/page_alloc.c:2973
 discard_slab mm/slub.c:3346 [inline]
 __put_partials+0x127/0x160 mm/slub.c:3886
 qlink_free mm/kasan/quarantine.c:163 [inline]
 qlist_free_all+0x47/0xe0 mm/kasan/quarantine.c:179
 kasan_quarantine_reduce+0x1a0/0x1f0 mm/kasan/quarantine.c:286
 __kasan_slab_alloc+0x4e/0x70 mm/kasan/common.c:350
 kasan_slab_alloc include/linux/kasan.h:253 [inline]
 slab_post_alloc_hook mm/slub.c:4953 [inline]
 slab_alloc_node mm/slub.c:5263 [inline]
 kmem_cache_alloc_node_noprof+0x292/0x7d0 mm/slub.c:5315
 __alloc_skb+0x156/0x410 net/core/skbuff.c:679
 alloc_skb include/linux/skbuff.h:1383 [inline]
 netlink_alloc_large_skb+0x69/0x150 net/netlink/af_netlink.c:1184
 netlink_sendmsg+0x680/0xda0 net/netlink/af_netlink.c:1869
 sock_sendmsg_nosec net/socket.c:727 [inline]
 __sock_sendmsg net/socket.c:742 [inline]
 ____sys_sendmsg+0xa54/0xc30 net/socket.c:2592
 ___sys_sendmsg+0x190/0x1e0 net/socket.c:2646
 __sys_sendmsg+0x170/0x220 net/socket.c:2678
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xc9/0x570 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
 ffff88813572c100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88813572c180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88813572c200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                         ^
 ffff88813572c280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88813572c300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


---
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Re: [syzbot] [media?] KASAN: slab-use-after-free Read in em28xx_unregister_media_device

[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit:    ba3e43a9e601 Merge tag 'soc-fixes-7.1-2' of git://git.kern..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=14e40f2e580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=8118209836970b54
dashboard link: https://syzkaller.appspot.com/bug?extid=07b93bb3189febcab189
compiler:       gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=11d79f2e580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=15a19a86580000

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-ba3e43a9.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/12db9228338c/vmlinux-ba3e43a9.xz
kernel image: https://storage.googleapis.com/syzbot-assets/c8dfb3210b18/bzImage-ba3e43a9.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+07b93bb3189febcab189@syzkaller.appspotmail.com

em28xx 5-1:0.132: Closing input extension
==================================================================
BUG: KASAN: slab-use-after-free in media_device_unregister drivers/media/mc/mc-device.c:833 [inline]
BUG: KASAN: slab-use-after-free in media_device_unregister+0x59d/0x610 drivers/media/mc/mc-device.c:811
Read of size 8 at addr ffff888031920210 by task kworker/3:1/39

CPU: 3 UID: 0 PID: 39 Comm: kworker/3:1 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
Workqueue: usb_hub_wq hub_event
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/0x1d0 mm/kasan/report.c:595
 media_device_unregister drivers/media/mc/mc-device.c:833 [inline]
 media_device_unregister+0x59d/0x610 drivers/media/mc/mc-device.c:811
 em28xx_unregister_media_device+0x4e/0xe0 drivers/media/usb/em28xx/em28xx-cards.c:3714
 em28xx_release_resources+0x79/0x1b0 drivers/media/usb/em28xx/em28xx-cards.c:3735
 em28xx_usb_disconnect.cold+0x17d/0x253 drivers/media/usb/em28xx/em28xx-cards.c:4427
 usb_unbind_interface+0x1dd/0x9e0 drivers/usb/core/driver.c:458
 device_remove drivers/base/dd.c:621 [inline]
 device_remove+0x12a/0x180 drivers/base/dd.c:613
 __device_release_driver drivers/base/dd.c:1352 [inline]
 device_release_driver_internal+0x44e/0x620 drivers/base/dd.c:1375
 bus_remove_device+0x2bc/0x560 drivers/base/bus.c:657
 device_del+0x376/0x9b0 drivers/base/core.c:3895
 usb_disable_device+0x367/0x810 drivers/usb/core/message.c:1478
 usb_disconnect+0x2e2/0x9a0 drivers/usb/core/hub.c:2345
 hub_port_connect drivers/usb/core/hub.c:5407 [inline]
 hub_port_connect_change drivers/usb/core/hub.c:5707 [inline]
 port_event drivers/usb/core/hub.c:5871 [inline]
 hub_event+0x1d0c/0x4af0 drivers/usb/core/hub.c:5953
 process_one_work+0xa0e/0x1980 kernel/workqueue.c:3314
 process_scheduled_works kernel/workqueue.c:3397 [inline]
 worker_thread+0x5ef/0xe50 kernel/workqueue.c:3478
 kthread+0x370/0x450 kernel/kthread.c:436
 ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>

Allocated by task 6029:
 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
 kmalloc_noprof include/linux/slab.h:950 [inline]
 kzalloc_noprof include/linux/slab.h:1188 [inline]
 em28xx_v4l2_init.cold+0x94/0x3a40 drivers/media/usb/em28xx/em28xx-video.c:2707
 em28xx_init_extension+0x13a/0x200 drivers/media/usb/em28xx/em28xx-core.c:1248
 request_module_async+0x61/0x80 drivers/media/usb/em28xx/em28xx-cards.c:3660
 process_one_work+0xa0e/0x1980 kernel/workqueue.c:3314
 process_scheduled_works kernel/workqueue.c:3397 [inline]
 worker_thread+0x5ef/0xe50 kernel/workqueue.c:3478
 kthread+0x370/0x450 kernel/kthread.c:436
 ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

Freed by task 6029:
 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:2689 [inline]
 slab_free mm/slub.c:6251 [inline]
 kfree+0x223/0x6c0 mm/slub.c:6566
 kref_put.isra.0+0x53/0x75 include/linux/kref.h:65
 em28xx_v4l2_init.cold+0x280/0x3a40 drivers/media/usb/em28xx/em28xx-video.c:3078
 em28xx_init_extension+0x13a/0x200 drivers/media/usb/em28xx/em28xx-core.c:1248
 request_module_async+0x61/0x80 drivers/media/usb/em28xx/em28xx-cards.c:3660
 process_one_work+0xa0e/0x1980 kernel/workqueue.c:3314
 process_scheduled_works kernel/workqueue.c:3397 [inline]
 worker_thread+0x5ef/0xe50 kernel/workqueue.c:3478
 kthread+0x370/0x450 kernel/kthread.c:436
 ret_from_fork+0x72b/0xd50 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 ffff888031920000
 which belongs to the cache kmalloc-8k of size 8192
The buggy address is located 528 bytes inside of
 freed 8192-byte region [ffff888031920000, ffff888031922000)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x31920
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0xfff00000000040(head|node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000040 ffff88801b843180 dead000000000100 dead000000000122
raw: 0000000000000000 0000000800020002 00000000f5000000 0000000000000000
head: 00fff00000000040 ffff88801b843180 dead000000000100 dead000000000122
head: 0000000000000000 0000000800020002 00000000f5000000 0000000000000000
head: 00fff00000000003 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 0xd28c0(GFP_NOWAIT|__GFP_IO|__GFP_FS|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 5825, tgid 5825 (syz-executor), ts 84598166672, free_ts 20468208603
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0xfd/0x120 mm/page_alloc.c:1853
 prep_new_page mm/page_alloc.c:1861 [inline]
 get_page_from_freelist+0x11a6/0x3410 mm/page_alloc.c:3941
 __alloc_frozen_pages_noprof+0x27c/0x2bc0 mm/page_alloc.c:5221
 alloc_slab_page mm/slub.c:3278 [inline]
 allocate_slab mm/slub.c:3467 [inline]
 new_slab+0xa6/0x6c0 mm/slub.c:3525
 refill_objects+0x277/0x420 mm/slub.c:7272
 refill_sheaf mm/slub.c:2816 [inline]
 __pcs_replace_empty_main+0x375/0x650 mm/slub.c:4652
 alloc_from_pcs mm/slub.c:4750 [inline]
 slab_alloc_node mm/slub.c:4884 [inline]
 __do_kmalloc_node mm/slub.c:5295 [inline]
 __kvmalloc_node_noprof+0x7da/0xa00 mm/slub.c:6833
 kvmalloc_array_node_noprof include/linux/slab.h:1216 [inline]
 __ptr_ring_init_queue_alloc_noprof include/linux/ptr_ring.h:481 [inline]
 ptr_ring_init_noprof include/linux/ptr_ring.h:499 [inline]
 wg_packet_queue_init+0x9a/0x360 drivers/net/wireguard/queueing.c:32
 wg_newlink+0x2fa/0x7a0 drivers/net/wireguard/device.c:352
 rtnl_newlink_create net/core/rtnetlink.c:3864 [inline]
 __rtnl_newlink net/core/rtnetlink.c:3995 [inline]
 rtnl_newlink+0x1499/0x2380 net/core/rtnetlink.c:4110
 rtnetlink_rcv_msg+0x95e/0xe90 net/core/rtnetlink.c:6997
 netlink_rcv_skb+0x159/0x420 net/netlink/af_netlink.c:2555
 netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
 netlink_unicast+0x585/0x850 net/netlink/af_netlink.c:1344
 netlink_sendmsg+0x8b0/0xda0 net/netlink/af_netlink.c:1899
 sock_sendmsg_nosec net/socket.c:787 [inline]
 __sock_sendmsg net/socket.c:802 [inline]
 __sys_sendto+0x468/0x4b0 net/socket.c:2265
 __do_sys_sendto net/socket.c:2272 [inline]
 __se_sys_sendto net/socket.c:2268 [inline]
 __x64_sys_sendto+0xe0/0x1c0 net/socket.c:2268
page last free pid 53 tgid 53 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 __free_pages_prepare mm/page_alloc.c:1397 [inline]
 __free_frozen_pages+0x794/0x10a0 mm/page_alloc.c:2938
 vfree mm/vmalloc.c:3472 [inline]
 vfree+0x15f/0x8d0 mm/vmalloc.c:3436
 delayed_vfree_work+0x56/0x80 mm/vmalloc.c:3392
 process_one_work+0xa0e/0x1980 kernel/workqueue.c:3314
 process_scheduled_works kernel/workqueue.c:3397 [inline]
 worker_thread+0x5ef/0xe50 kernel/workqueue.c:3478
 kthread+0x370/0x450 kernel/kthread.c:436
 ret_from_fork+0x72b/0xd50 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:
 ffff888031920100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888031920180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888031920200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                         ^
 ffff888031920280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888031920300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


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