Hello,
syzbot found the following issue on:
HEAD commit: 26260251022f Merge tag 'livepatching-for-7.3' of git://git..
git tree: upstream
console output:
https://syzkaller.appspot.com/x/log.txt?x=11e10625580000
kernel config:
https://syzkaller.appspot.com/x/.config?x=54b0fd32feaa7e7d
dashboard link:
https://syzkaller.appspot.com/bug?extid=37578f730d38898f4b74
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/009830dc9804/disk-26260251.raw.xz
vmlinux:
https://storage.googleapis.com/syzbot-assets/56e3e1e4edb1/vmlinux-26260251.xz
kernel image:
https://storage.googleapis.com/syzbot-assets/3114315782db/bzImage-26260251.xz
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by:
syzbot+37578f...@syzkaller.appspotmail.com
==================================================================
BUG: KASAN: slab-use-after-free in dvb_media_device_free+0x589/0x650 drivers/media/dvb-core/dvbdev.c:210
Read of size 8 at addr ffff88802d1dfab0 by task syz.4.4145/19619
CPU: 1 UID: 0 PID: 19619 Comm: syz.4.4145 Tainted: G L syzkaller #0 PREEMPT(full)
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026
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
dvb_media_device_free+0x589/0x650 drivers/media/dvb-core/dvbdev.c:210
dvb_remove_device.part.0+0xa4/0x270 drivers/media/dvb-core/dvbdev.c:604
dvb_remove_device+0x1f/0x30 drivers/media/dvb-core/dvbdev.c:596
dvb_unregister_frontend+0x7a/0x150 drivers/media/dvb-core/dvb_frontend.c:3103
vidtv_bridge_remove+0x84/0x140 drivers/media/test-drivers/vidtv/vidtv_bridge.c:554
platform_remove+0x5f/0x80 drivers/base/platform.c:1524
device_remove+0xcb/0x180 drivers/base/dd.c:616
__device_release_driver drivers/base/dd.c:1349 [inline]
device_release_driver_internal+0x44e/0x620 drivers/base/dd.c:1372
unbind_store+0xf8/0x110 drivers/base/bus.c:244
drv_attr_store+0x74/0xb0 drivers/base/bus.c:125
sysfs_kf_write+0xf2/0x150 fs/sysfs/file.c:145
kernfs_fop_write_iter+0x3e0/0x5f0 fs/kernfs/file.c:345
new_sync_write fs/read_write.c:595 [inline]
vfs_write+0x6af/0x1050 fs/read_write.c:687
ksys_write+0x12a/0x250 fs/read_write.c:739
do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
do_syscall_64+0x123/0x790 arch/x86/entry/syscall_64.c:84
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f2f66f9e0d9
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f2f67e18028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f2f67226090 RCX: 00007f2f66f9e0d9
RDX: 0000000000000007 RSI: 0000200000000300 RDI: 0000000000000004
RBP: 00007f2f67035024 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f2f67226128 R14: 00007f2f67226090 R15: 00007ffd283e24d8
</TASK>
Allocated by task 1:
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+0x2e7/0x6b0 mm/slub.c:5484
_kmalloc_noprof include/linux/slab.h:988 [inline]
_kzalloc_noprof include/linux/slab.h:1309 [inline]
dvb_register_device+0x1d6/0x1e20 drivers/media/dvb-core/dvbdev.c:472
dvb_register_frontend+0x552/0x820 drivers/media/dvb-core/dvb_frontend.c:3074
vidtv_bridge_dvb_init drivers/media/test-drivers/vidtv/vidtv_bridge.c:438 [inline]
vidtv_bridge_probe+0x44b/0xa30 drivers/media/test-drivers/vidtv/vidtv_bridge.c:510
platform_probe+0x106/0x1d0 drivers/base/platform.c:1507
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
__driver_attach+0x21f/0x5b0 drivers/base/dd.c:1292
bus_for_each_dev+0x13e/0x1d0 drivers/base/bus.c:383
bus_add_driver+0x305/0x5b0 drivers/base/bus.c:763
driver_register+0x1e2/0x360 drivers/base/driver.c:174
vidtv_bridge_init+0x52/0x80 drivers/media/test-drivers/vidtv/vidtv_bridge.c:602
do_one_initcall+0x11c/0x6f0 init/main.c:1353
do_initcall_level init/main.c:1415 [inline]
do_initcalls init/main.c:1431 [inline]
do_basic_setup init/main.c:1451 [inline]
kernel_init_freeable+0x6ea/0x7b0 init/main.c:1666
kernel_init+0x21/0x1e0 init/main.c:1556
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 19619:
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:2678 [inline]
slab_free mm/slub.c:6372 [inline]
kfree+0x22b/0x6c0 mm/slub.c:6687
dvb_free_device drivers/media/dvb-core/dvbdev.c:616 [inline]
kref_put include/linux/kref.h:65 [inline]
dvb_device_put.part.0+0x57/0x90 drivers/media/dvb-core/dvbdev.c:629
dvb_device_put drivers/media/dvb-core/dvbdev.c:628 [inline]
dvb_remove_device.part.0+0x90/0x270 drivers/media/dvb-core/dvbdev.c:601
dvb_remove_device+0x1f/0x30 drivers/media/dvb-core/dvbdev.c:596
dvb_unregister_frontend+0x7a/0x150 drivers/media/dvb-core/dvb_frontend.c:3103
vidtv_bridge_remove+0x84/0x140 drivers/media/test-drivers/vidtv/vidtv_bridge.c:554
platform_remove+0x5f/0x80 drivers/base/platform.c:1524
device_remove+0xcb/0x180 drivers/base/dd.c:616
__device_release_driver drivers/base/dd.c:1349 [inline]
device_release_driver_internal+0x44e/0x620 drivers/base/dd.c:1372
unbind_store+0xf8/0x110 drivers/base/bus.c:244
drv_attr_store+0x74/0xb0 drivers/base/bus.c:125
sysfs_kf_write+0xf2/0x150 fs/sysfs/file.c:145
kernfs_fop_write_iter+0x3e0/0x5f0 fs/kernfs/file.c:345
new_sync_write fs/read_write.c:595 [inline]
vfs_write+0x6af/0x1050 fs/read_write.c:687
ksys_write+0x12a/0x250 fs/read_write.c:739
do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
do_syscall_64+0x123/0x790 arch/x86/entry/syscall_64.c:84
entry_SYSCALL_64_after_hwframe+0x77/0x7f
The buggy address belongs to the object at ffff88802d1dfa00
which belongs to the cache kmalloc-256 of size 256
The buggy address is located 176 bytes inside of
freed 256-byte region [ffff88802d1dfa00, ffff88802d1dfb00)
The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x2d1de
head: order:1 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 ffff88801c027b40 dead000000000100 dead000000000122
raw: 0000000000000000 0000000800100010 00000000f5000000 0000000000000000
head: 00fff00000000040 ffff88801c027b40 dead000000000100 dead000000000122
head: 0000000000000000 0000000800100010 00000000f5000000 0000000000000000
head: 00fff00000000001 ffffffffffffff81 00000000ffffffff 00000000ffffffff
head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000002
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 1, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 1, tgid 1 (swapper/0), ts 17295453492
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/0x35b0 mm/page_alloc.c:3943
__alloc_frozen_pages_noprof+0x2eb/0x3300 mm/page_alloc.c:5436
alloc_slab_page mm/slub.c:3267 [inline]
allocate_slab mm/slub.c:3382 [inline]
new_slab+0xa5/0x640 mm/slub.c:3428
refill_objects+0xe3/0x410 mm/slub.c:7305
refill_sheaf mm/slub.c:2805 [inline]
__pcs_replace_empty_main+0x372/0x680 mm/slub.c:4677
alloc_from_pcs mm/slub.c:4775 [inline]
slab_alloc_node mm/slub.c:4907 [inline]
__kmalloc_cache_noprof+0x47b/0x6b0 mm/slub.c:5480
_kmalloc_noprof include/linux/slab.h:988 [inline]
_kzalloc_noprof include/linux/slab.h:1309 [inline]
bus_add_driver+0x92/0x5b0 drivers/base/bus.c:747
driver_register+0x1e2/0x360 drivers/base/driver.c:174
usb_register_driver drivers/usb/core/driver.c:1078 [inline]
usb_register_driver+0x21c/0x3e0 drivers/usb/core/driver.c:1060
do_one_initcall+0x11c/0x6f0 init/main.c:1353
do_initcall_level init/main.c:1415 [inline]
do_initcalls init/main.c:1431 [inline]
do_basic_setup init/main.c:1451 [inline]
kernel_init_freeable+0x6ea/0x7b0 init/main.c:1666
kernel_init+0x21/0x1e0 init/main.c:1556
ret_from_fork+0x730/0xd60 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
page_owner free stack trace missing
Memory state around the buggy address:
ffff88802d1df980: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88802d1dfa00: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88802d1dfa80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88802d1dfb00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88802d1dfb80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================
==================================================================
BUG: KASAN: slab-use-after-free in dvb_media_device_free+0x5d1/0x650 drivers/media/dvb-core/dvbdev.c:212
Read of size 8 at addr ffff88802d1dfab0 by task syz.4.4145/19619
CPU: 1 UID: 0 PID: 19619 Comm: syz.4.4145 Tainted: G B L syzkaller #0 PREEMPT(full)
Tainted: [B]=BAD_PAGE, [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026
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
dvb_media_device_free+0x5d1/0x650 drivers/media/dvb-core/dvbdev.c:212
dvb_remove_device.part.0+0xa4/0x270 drivers/media/dvb-core/dvbdev.c:604
dvb_remove_device+0x1f/0x30 drivers/media/dvb-core/dvbdev.c:596
dvb_unregister_frontend+0x7a/0x150 drivers/media/dvb-core/dvb_frontend.c:3103
vidtv_bridge_remove+0x84/0x140 drivers/media/test-drivers/vidtv/vidtv_bridge.c:554
platform_remove+0x5f/0x80 drivers/base/platform.c:1524
device_remove+0xcb/0x180 drivers/base/dd.c:616
__device_release_driver drivers/base/dd.c:1349 [inline]
device_release_driver_internal+0x44e/0x620 drivers/base/dd.c:1372
unbind_store+0xf8/0x110 drivers/base/bus.c:244
drv_attr_store+0x74/0xb0 drivers/base/bus.c:125
sysfs_kf_write+0xf2/0x150 fs/sysfs/file.c:145
kernfs_fop_write_iter+0x3e0/0x5f0 fs/kernfs/file.c:345
new_sync_write fs/read_write.c:595 [inline]
vfs_write+0x6af/0x1050 fs/read_write.c:687
ksys_write+0x12a/0x250 fs/read_write.c:739
do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
do_syscall_64+0x123/0x790 arch/x86/entry/syscall_64.c:84
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f2f66f9e0d9
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f2f67e18028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f2f67226090 RCX: 00007f2f66f9e0d9
RDX: 0000000000000007 RSI: 0000200000000300 RDI: 0000000000000004
RBP: 00007f2f67035024 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f2f67226128 R14: 00007f2f67226090 R15: 00007ffd283e24d8
</TASK>
Allocated by task 1:
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+0x2e7/0x6b0 mm/slub.c:5484
_kmalloc_noprof include/linux/slab.h:988 [inline]
_kzalloc_noprof include/linux/slab.h:1309 [inline]
dvb_register_device+0x1d6/0x1e20 drivers/media/dvb-core/dvbdev.c:472
dvb_register_frontend+0x552/0x820 drivers/media/dvb-core/dvb_frontend.c:3074
vidtv_bridge_dvb_init drivers/media/test-drivers/vidtv/vidtv_bridge.c:438 [inline]
vidtv_bridge_probe+0x44b/0xa30 drivers/media/test-drivers/vidtv/vidtv_bridge.c:510
platform_probe+0x106/0x1d0 drivers/base/platform.c:1507
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
__driver_attach+0x21f/0x5b0 drivers/base/dd.c:1292
bus_for_each_dev+0x13e/0x1d0 drivers/base/bus.c:383
bus_add_driver+0x305/0x5b0 drivers/base/bus.c:763
driver_register+0x1e2/0x360 drivers/base/driver.c:174
vidtv_bridge_init+0x52/0x80 drivers/media/test-drivers/vidtv/vidtv_bridge.c:602
do_one_initcall+0x11c/0x6f0 init/main.c:1353
do_initcall_level init/main.c:1415 [inline]
do_initcalls init/main.c:1431 [inline]
do_basic_setup init/main.c:1451 [inline]
kernel_init_freeable+0x6ea/0x7b0 init/main.c:1666
kernel_init+0x21/0x1e0 init/main.c:1556
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 19619:
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:2678 [inline]
slab_free mm/slub.c:6372 [inline]
kfree+0x22b/0x6c0 mm/slub.c:6687
dvb_free_device drivers/media/dvb-core/dvbdev.c:616 [inline]
kref_put include/linux/kref.h:65 [inline]
dvb_device_put.part.0+0x57/0x90 drivers/media/dvb-core/dvbdev.c:629
dvb_device_put drivers/media/dvb-core/dvbdev.c:628 [inline]
dvb_remove_device.part.0+0x90/0x270 drivers/media/dvb-core/dvbdev.c:601
dvb_remove_device+0x1f/0x30 drivers/media/dvb-core/dvbdev.c:596
dvb_unregister_frontend+0x7a/0x150 drivers/media/dvb-core/dvb_frontend.c:3103
vidtv_bridge_remove+0x84/0x140 drivers/media/test-drivers/vidtv/vidtv_bridge.c:554
platform_remove+0x5f/0x80 drivers/base/platform.c:1524
device_remove+0xcb/0x180 drivers/base/dd.c:616
__device_release_driver drivers/base/dd.c:1349 [inline]
device_release_driver_internal+0x44e/0x620 drivers/base/dd.c:1372
unbind_store+0xf8/0x110 drivers/base/bus.c:244
drv_attr_store+0x74/0xb0 drivers/base/bus.c:125
sysfs_kf_write+0xf2/0x150 fs/sysfs/file.c:145
kernfs_fop_write_iter+0x3e0/0x5f0 fs/kernfs/file.c:345
new_sync_write fs/read_write.c:595 [inline]
vfs_write+0x6af/0x1050 fs/read_write.c:687
ksys_write+0x12a/0x250 fs/read_write.c:739
do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
do_syscall_64+0x123/0x790 arch/x86/entry/syscall_64.c:84
entry_SYSCALL_64_after_hwframe+0x77/0x7f
The buggy address belongs to the object at ffff88802d1dfa00
which belongs to the cache kmalloc-256 of size 256
The buggy address is located 176 bytes inside of
freed 256-byte region [ffff88802d1dfa00, ffff88802d1dfb00)
The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x2d1de
head: order:1 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 ffff88801c027b40 dead000000000100 dead000000000122
raw: 0000000000000000 0000000800100010 00000000f5000000 0000000000000000
head: 00fff00000000040 ffff88801c027b40 dead000000000100 dead000000000122
head: 0000000000000000 0000000800100010 00000000f5000000 0000000000000000
head: 00fff00000000001 ffffffffffffff81 00000000ffffffff 00000000ffffffff
head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000002
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 1, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 1, tgid 1 (swapper/0), ts 17295453492
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/0x35b0 mm/page_alloc.c:3943
__alloc_frozen_pages_noprof+0x2eb/0x3300 mm/page_alloc.c:5436
alloc_slab_page mm/slub.c:3267 [inline]
allocate_slab mm/slub.c:3382 [inline]
new_slab+0xa5/0x640 mm/slub.c:3428
refill_objects+0xe3/0x410 mm/slub.c:7305
refill_sheaf mm/slub.c:2805 [inline]
__pcs_replace_empty_main+0x372/0x680 mm/slub.c:4677
alloc_from_pcs mm/slub.c:4775 [inline]
slab_alloc_node mm/slub.c:4907 [inline]
__kmalloc_cache_noprof+0x47b/0x6b0 mm/slub.c:5480
_kmalloc_noprof include/linux/slab.h:988 [inline]
_kzalloc_noprof include/linux/slab.h:1309 [inline]
bus_add_driver+0x92/0x5b0 drivers/base/bus.c:747
driver_register+0x1e2/0x360 drivers/base/driver.c:174
usb_register_driver drivers/usb/core/driver.c:1078 [inline]
usb_register_driver+0x21c/0x3e0 drivers/usb/core/driver.c:1060
do_one_initcall+0x11c/0x6f0 init/main.c:1353
do_initcall_level init/main.c:1415 [inline]
do_initcalls init/main.c:1431 [inline]
do_basic_setup init/main.c:1451 [inline]
kernel_init_freeable+0x6ea/0x7b0 init/main.c:1666
kernel_init+0x21/0x1e0 init/main.c:1556
ret_from_fork+0x730/0xd60 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
page_owner free stack trace missing
Memory state around the buggy address:
ffff88802d1df980: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88802d1dfa00: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88802d1dfa80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88802d1dfb00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88802d1dfb80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================
==================================================================
BUG: KASAN: slab-use-after-free in dvb_media_device_free+0x5eb/0x650 drivers/media/dvb-core/dvbdev.c:213
Read of size 8 at addr ffff88802d1dfac0 by task syz.4.4145/19619
CPU: 1 UID: 0 PID: 19619 Comm: syz.4.4145 Tainted: G B L syzkaller #0 PREEMPT(full)
Tainted: [B]=BAD_PAGE, [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026
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
dvb_media_device_free+0x5eb/0x650 drivers/media/dvb-core/dvbdev.c:213
dvb_remove_device.part.0+0xa4/0x270 drivers/media/dvb-core/dvbdev.c:604
dvb_remove_device+0x1f/0x30 drivers/media/dvb-core/dvbdev.c:596
dvb_unregister_frontend+0x7a/0x150 drivers/media/dvb-core/dvb_frontend.c:3103
vidtv_bridge_remove+0x84/0x140 drivers/media/test-drivers/vidtv/vidtv_bridge.c:554
platform_remove+0x5f/0x80 drivers/base/platform.c:1524
device_remove+0xcb/0x180 drivers/base/dd.c:616
__device_release_driver drivers/base/dd.c:1349 [inline]
device_release_driver_internal+0x44e/0x620 drivers/base/dd.c:1372
unbind_store+0xf8/0x110 drivers/base/bus.c:244
drv_attr_store+0x74/0xb0 drivers/base/bus.c:125
sysfs_kf_write+0xf2/0x150 fs/sysfs/file.c:145
kernfs_fop_write_iter+0x3e0/0x5f0 fs/kernfs/file.c:345
new_sync_write fs/read_write.c:595 [inline]
vfs_write+0x6af/0x1050 fs/read_write.c:687
ksys_write+0x12a/0x250 fs/read_write.c:739
do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
do_syscall_64+0x123/0x790 arch/x86/entry/syscall_64.c:84
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f2f66f9e0d9
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f2f67e18028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f2f67226090 RCX: 00007f2f66f9e0d9
RDX: 0000000000000007 RSI: 0000200000000300 RDI: 0000000000000004
RBP: 00007f2f67035024 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f2f67226128 R14: 00007f2f67226090 R15: 00007ffd283e24d8
</TASK>
Allocated by task 1:
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+0x2e7/0x6b0 mm/slub.c:5484
_kmalloc_noprof include/linux/slab.h:988 [inline]
_kzalloc_noprof include/linux/slab.h:1309 [inline]
dvb_register_device+0x1d6/0x1e20 drivers/media/dvb-core/dvbdev.c:472
dvb_register_frontend+0x552/0x820 drivers/media/dvb-core/dvb_frontend.c:3074
vidtv_bridge_dvb_init drivers/media/test-drivers/vidtv/vidtv_bridge.c:438 [inline]
vidtv_bridge_probe+0x44b/0xa30 drivers/media/test-drivers/vidtv/vidtv_bridge.c:510
platform_probe+0x106/0x1d0 drivers/base/platform.c:1507
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
__driver_attach+0x21f/0x5b0 drivers/base/dd.c:1292
bus_for_each_dev+0x13e/0x1d0 drivers/base/bus.c:383
bus_add_driver+0x305/0x5b0 drivers/base/bus.c:763
driver_register+0x1e2/0x360 drivers/base/driver.c:174
vidtv_bridge_init+0x52/0x80 drivers/media/test-drivers/vidtv/vidtv_bridge.c:602
do_one_initcall+0x11c/0x6f0 init/main.c:1353
do_initcall_level init/main.c:1415 [inline]
do_initcalls init/main.c:1431 [inline]
do_basic_setup init/main.c:1451 [inline]
kernel_init_freeable+0x6ea/0x7b0 init/main.c:1666
kernel_init+0x21/0x1e0 init/main.c:1556
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 19619:
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:2678 [inline]
slab_free mm/slub.c:6372 [inline]
kfree+0x22b/0x6c0 mm/slub.c:6687
dvb_free_device drivers/media/dvb-core/dvbdev.c:616 [inline]
kref_put include/linux/kref.h:65 [inline]
dvb_device_put.part.0+0x57/0x90 drivers/media/dvb-core/dvbdev.c:629
dvb_device_put drivers/media/dvb-core/dvbdev.c:628 [inline]
dvb_remove_device.part.0+0x90/0x270 drivers/media/dvb-core/dvbdev.c:601
dvb_remove_device+0x1f/0x30 drivers/media/dvb-core/dvbdev.c:596
dvb_unregister_frontend+0x7a/0x150 drivers/media/dvb-core/dvb_frontend.c:3103
vidtv_bridge_remove+0x84/0x140 drivers/media/test-drivers/vidtv/vidtv_bridge.c:554
platform_remove+0x5f/0x80 drivers/base/platform.c:1524
device_remove+0xcb/0x180 drivers/base/dd.c:616
__device_release_driver drivers/base/dd.c:1349 [inline]
device_release_driver_internal+0x44e/0x620 drivers/base/dd.c:1372
unbind_store+0xf8/0x110 drivers/base/bus.c:244
drv_attr_store+0x74/0xb0 drivers/base/bus.c:125
sysfs_kf_write+0xf2/0x150 fs/sysfs/file.c:145
kernfs_fop_write_iter+0x3e0/0x5f0 fs/kernfs/file.c:345
new_sync_write fs/read_write.c:595 [inline]
vfs_write+0x6af/0x1050 fs/read_write.c:687
ksys_write+0x12a/0x250 fs/read_write.c:739
do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
do_syscall_64+0x123/0x790 arch/x86/entry/syscall_64.c:84
entry_SYSCALL_64_after_hwframe+0x77/0x7f
The buggy address belongs to the object at ffff88802d1dfa00
which belongs to the cache kmalloc-256 of size 256
The buggy address is located 192 bytes inside of
freed 256-byte region [ffff88802d1dfa00, ffff88802d1dfb00)
The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x2d1de
head: order:1 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 ffff88801c027b40 dead000000000100 dead000000000122
raw: 0000000000000000 0000000800100010 00000000f5000000 0000000000000000
head: 00fff00000000040 ffff88801c027b40 dead000000000100 dead000000000122
head: 0000000000000000 0000000800100010 00000000f5000000 0000000000000000
head: 00fff00000000001 ffffffffffffff81 00000000ffffffff 00000000ffffffff
head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000002
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 1, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 1, tgid 1 (swapper/0), ts 17295453492
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/0x35b0 mm/page_alloc.c:3943
__alloc_frozen_pages_noprof+0x2eb/0x3300 mm/page_alloc.c:5436
alloc_slab_page mm/slub.c:3267 [inline]
allocate_slab mm/slub.c:3382 [inline]
new_slab+0xa5/0x640 mm/slub.c:3428
refill_objects+0xe3/0x410 mm/slub.c:7305
refill_sheaf mm/slub.c:2805 [inline]
__pcs_replace_empty_main+0x372/0x680 mm/slub.c:4677
alloc_from_pcs mm/slub.c:4775 [inline]
slab_alloc_node mm/slub.c:4907 [inline]
__kmalloc_cache_noprof+0x47b/0x6b0 mm/slub.c:5480
_kmalloc_noprof include/linux/slab.h:988 [inline]
_kzalloc_noprof include/linux/slab.h:1309 [inline]
bus_add_driver+0x92/0x5b0 drivers/base/bus.c:747
driver_register+0x1e2/0x360 drivers/base/driver.c:174
usb_register_driver drivers/usb/core/driver.c:1078 [inline]
usb_register_driver+0x21c/0x3e0 drivers/usb/core/driver.c:1060
do_one_initcall+0x11c/0x6f0 init/main.c:1353
do_initcall_level init/main.c:1415 [inline]
do_initcalls init/main.c:1431 [inline]
do_basic_setup init/main.c:1451 [inline]
kernel_init_freeable+0x6ea/0x7b0 init/main.c:1666
kernel_init+0x21/0x1e0 init/main.c:1556
ret_from_fork+0x730/0xd60 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
page_owner free stack trace missing
Memory state around the buggy address:
ffff88802d1df980: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88802d1dfa00: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88802d1dfa80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88802d1dfb00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88802d1dfb80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================
==================================================================
BUG: KASAN: slab-use-after-free in dvb_media_device_free+0x5de/0x650 drivers/media/dvb-core/dvbdev.c:214
Write of size 8 at addr ffff88802d1dfab0 by task syz.4.4145/19619
CPU: 1 UID: 0 PID: 19619 Comm: syz.4.4145 Tainted: G B L syzkaller #0 PREEMPT(full)
Tainted: [B]=BAD_PAGE, [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026
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
dvb_media_device_free+0x5de/0x650 drivers/media/dvb-core/dvbdev.c:214
dvb_remove_device.part.0+0xa4/0x270 drivers/media/dvb-core/dvbdev.c:604
dvb_remove_device+0x1f/0x30 drivers/media/dvb-core/dvbdev.c:596
dvb_unregister_frontend+0x7a/0x150 drivers/media/dvb-core/dvb_frontend.c:3103
vidtv_bridge_remove+0x84/0x140 drivers/media/test-drivers/vidtv/vidtv_bridge.c:554
platform_remove+0x5f/0x80 drivers/base/platform.c:1524
device_remove+0xcb/0x180 drivers/base/dd.c:616
__device_release_driver drivers/base/dd.c:1349 [inline]
device_release_driver_internal+0x44e/0x620 drivers/base/dd.c:1372
unbind_store+0xf8/0x110 drivers/base/bus.c:244
drv_attr_store+0x74/0xb0 drivers/base/bus.c:125
sysfs_kf_write+0xf2/0x150 fs/sysfs/file.c:145
kernfs_fop_write_iter+0x3e0/0x5f0 fs/kernfs/file.c:345
new_sync_write fs/read_write.c:595 [inline]
vfs_write+0x6af/0x1050 fs/read_write.c:687
ksys_write+0x12a/0x250 fs/read_write.c:739
do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
do_syscall_64+0x123/0x790 arch/x86/entry/syscall_64.c:84
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f2f66f9e0d9
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f2f67e18028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f2f67226090 RCX: 00007f2f66f9e0d9
RDX: 0000000000000007 RSI: 0000200000000300 RDI: 0000000000000004
RBP: 00007f2f67035024 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f2f67226128 R14: 00007f2f67226090 R15: 00007ffd283e24d8
</TASK>
Allocated by task 1:
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+0x2e7/0x6b0 mm/slub.c:5484
_kmalloc_noprof include/linux/slab.h:988 [inline]
_kzalloc_noprof include/linux/slab.h:1309 [inline]
dvb_register_device+0x1d6/0x1e20 drivers/media/dvb-core/dvbdev.c:472
dvb_register_frontend+0x552/0x820 drivers/media/dvb-core/dvb_frontend.c:3074
vidtv_bridge_dvb_init drivers/media/test-drivers/vidtv/vidtv_bridge.c:438 [inline]
vidtv_bridge_probe+0x44b/0xa30 drivers/media/test-drivers/vidtv/vidtv_bridge.c:510
platform_probe+0x106/0x1d0 drivers/base/platform.c:1507
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
__driver_attach+0x21f/0x5b0 drivers/base/dd.c:1292
bus_for_each_dev+0x13e/0x1d0 drivers/base/bus.c:383
bus_add_driver+0x305/0x5b0 drivers/base/bus.c:763
driver_register+0x1e2/0x360 drivers/base/driver.c:174
vidtv_bridge_init+0x52/0x80 drivers/media/test-drivers/vidtv/vidtv_bridge.c:602
do_one_initcall+0x11c/0x6f0 init/main.c:1353
do_initcall_level init/main.c:1415 [inline]
do_initcalls init/main.c:1431 [inline]
do_basic_setup init/main.c:1451 [inline]
kernel_init_freeable+0x6ea/0x7b0 init/main.c:1666
kernel_init+0x21/0x1e0 init/main.c:1556
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 19619:
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:2678 [inline]
slab_free mm/slub.c:6372 [inline]
kfree+0x22b/0x6c0 mm/slub.c:6687
dvb_free_device drivers/media/dvb-core/dvbdev.c:616 [inline]
kref_put include/linux/kref.h:65 [inline]
dvb_device_put.part.0+0x57/0x90 drivers/media/dvb-core/dvbdev.c:629
dvb_device_put drivers/media/dvb-core/dvbdev.c:628 [inline]
dvb_remove_device.part.0+0x90/0x270 drivers/media/dvb-core/dvbdev.c:601
dvb_remove_device+0x1f/0x30 drivers/media/dvb-core/dvbdev.c:596
dvb_unregister_frontend+0x7a/0x150 drivers/media/dvb-core/dvb_frontend.c:3103
vidtv_bridge_remove+0x84/0x140 drivers/media/test-drivers/vidtv/vidtv_bridge.c:554
platform_remove+0x5f/0x80 drivers/base/platform.c:1524
device_remove+0xcb/0x180 drivers/base/dd.c:616
__device_release_driver drivers/base/dd.c:1349 [inline]
device_release_driver_internal+0x44e/0x620 drivers/base/dd.c:1372
unbind_store+0xf8/0x110 drivers/base/bus.c:244
drv_attr_store+0x74/0xb0 drivers/base/bus.c:125
sysfs_kf_write+0xf2/0x150 fs/sysfs/file.c:145
kernfs_fop_write_iter+0x3e0/0x5f0 fs/kernfs/file.c:345
new_sync_write fs/read_write.c:595 [inline]
vfs_write+0x6af/0x1050 fs/read_write.c:687
ksys_write+0x12a/0x250 fs/read_write.c:739
do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
do_syscall_64+0x123/0x790 arch/x86/entry/syscall_64.c:84
entry_SYSCALL_64_after_hwframe+0x77/0x7f
The buggy address belongs to the object at ffff88802d1dfa00
which belongs to the cache kmalloc-256 of size 256
The buggy address is located 176 bytes inside of
freed 256-byte region [ffff88802d1dfa00, ffff88802d1dfb00)
The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x2d1de
head: order:1 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 ffff88801c027b40 dead000000000100 dead000000000122
raw: 0000000000000000 0000000800100010 00000000f5000000 0000000000000000
head: 00fff00000000040 ffff88801c027b40 dead000000000100 dead000000000122
head: 0000000000000000 0000000800100010 00000000f5000000 0000000000000000
head: 00fff00000000001 ffffffffffffff81 00000000ffffffff 00000000ffffffff
head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000002
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 1, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 1, tgid 1 (swapper/0), ts 17295453492
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/0x35b0 mm/page_alloc.c:3943
__alloc_frozen_pages_noprof+0x2eb/0x3300 mm/page_alloc.c:5436
alloc_slab_page mm/slub.c:3267 [inline]
allocate_slab mm/slub.c:3382 [inline]
new_slab+0xa5/0x640 mm/slub.c:3428
refill_objects+0xe3/0x410 mm/slub.c:7305
refill_sheaf mm/slub.c:2805 [inline]
__pcs_replace_empty_main+0x372/0x680 mm/slub.c:4677
alloc_from_pcs mm/slub.c:4775 [inline]
slab_alloc_node mm/slub.c:4907 [inline]
__kmalloc_cache_noprof+0x47b/0x6b0 mm/slub.c:5480
_kmalloc_noprof include/linux/slab.h:988 [inline]
_kzalloc_noprof include/linux/slab.h:1309 [inline]
bus_add_driver+0x92/0x5b0 drivers/base/bus.c:747
driver_register+0x1e2/0x360 drivers/base/driver.c:174
usb_register_driver drivers/usb/core/driver.c:1078 [inline]
usb_register_driver+0x21c/0x3e0 drivers/usb/core/driver.c:1060
do_one_initcall+0x11c/0x6f0 init/main.c:1353
do_initcall_level init/main.c:1415 [inline]
do_initcalls init/main.c:1431 [inline]
do_basic_setup init/main.c:1451 [inline]
kernel_init_freeable+0x6ea/0x7b0 init/main.c:1666
kernel_init+0x21/0x1e0 init/main.c:1556
ret_from_fork+0x730/0xd60 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
page_owner free stack trace missing
Memory state around the buggy address:
ffff88802d1df980: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88802d1dfa00: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88802d1dfa80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88802d1dfb00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88802d1dfb80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================
---
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