==================================================================
BUG: KASAN: use-after-free in instrument_atomic_read include/linux/instrumented.h:71 [inline]
BUG: KASAN: use-after-free in atomic_read include/linux/atomic/atomic-instrumented.h:27 [inline]
BUG: KASAN: use-after-free in refcount_read include/linux/refcount.h:147 [inline]
BUG: KASAN: use-after-free in skb_unref include/linux/skbuff.h:1131 [inline]
BUG: KASAN: use-after-free in consume_skb+0x3c/0x250 net/core/skbuff.c:926
Read of size 4 at addr ffff88811c0b786c by task syz-executor.0/345

CPU: 1 PID: 345 Comm: syz-executor.0 Not tainted 5.15.149-syzkaller-1069274-g85445b5a2107 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/02/2024
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x151/0x1b7 lib/dump_stack.c:106
 print_address_description+0x87/0x3b0 mm/kasan/report.c:248
 __kasan_report mm/kasan/report.c:427 [inline]
 kasan_report+0x179/0x1c0 mm/kasan/report.c:444
 kasan_check_range+0x293/0x2a0 mm/kasan/generic.c:189
 __kasan_check_read+0x11/0x20 mm/kasan/shadow.c:31
 instrument_atomic_read include/linux/instrumented.h:71 [inline]
 atomic_read include/linux/atomic/atomic-instrumented.h:27 [inline]
 refcount_read include/linux/refcount.h:147 [inline]
 skb_unref include/linux/skbuff.h:1131 [inline]
 consume_skb+0x3c/0x250 net/core/skbuff.c:926
 __sk_msg_free+0x2dd/0x370 net/core/skmsg.c:205
 sk_msg_free net/core/skmsg.c:218 [inline]
 __sk_psock_purge_ingress_msg net/core/skmsg.c:768 [inline]
 __sk_psock_zap_ingress net/core/skmsg.c:786 [inline]
 sk_psock_stop+0x44c/0x4d0 net/core/skmsg.c:804
 sock_map_close+0x2b9/0x4c0 net/core/sock_map.c:1548
 unix_release+0x82/0xc0 net/unix/af_unix.c:949
 __sock_release net/socket.c:649 [inline]
 sock_close+0xdf/0x270 net/socket.c:1336
 __fput+0x3fe/0x910 fs/file_table.c:280
 ____fput+0x15/0x20 fs/file_table.c:308
 task_work_run+0x129/0x190 kernel/task_work.c:164
 tracehook_notify_resume include/linux/tracehook.h:189 [inline]
 exit_to_user_mode_loop+0xc4/0xe0 kernel/entry/common.c:175
 exit_to_user_mode_prepare+0x5a/0xa0 kernel/entry/common.c:208
 __syscall_exit_to_user_mode_work kernel/entry/common.c:290 [inline]
 syscall_exit_to_user_mode+0x26/0x160 kernel/entry/common.c:301
 do_syscall_64+0x49/0xb0 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x61/0xcb
RIP: 0033:0x7f914cec4c9a
Code: 48 3d 00 f0 ff ff 77 48 c3 0f 1f 80 00 00 00 00 48 83 ec 18 89 7c 24 0c e8 03 7f 02 00 8b 7c 24 0c 89 c2 b8 03 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 36 89 d7 89 44 24 0c e8 63 7f 02 00 8b 44 24
RSP: 002b:00007ffe2eddc870 EFLAGS: 00000293 ORIG_RAX: 0000000000000003
RAX: 0000000000000000 RBX: 0000000000000004 RCX: 00007f914cec4c9a
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000003
RBP: 0000000000000032 R08: 0000001b30a60000 R09: 00007f914cff4f8c
R10: 00007ffe2eddc9c0 R11: 0000000000000293 R12: 00007f914ca4a1b0
R13: ffffffffffffffff R14: 00007f914ca49000 R15: 0000000000006fd1
 </TASK>

Allocated by task 346:
 kasan_save_stack mm/kasan/common.c:38 [inline]
 kasan_set_track mm/kasan/common.c:45 [inline]
 set_alloc_info mm/kasan/common.c:433 [inline]
 __kasan_slab_alloc+0xb1/0xe0 mm/kasan/common.c:466
 kasan_slab_alloc include/linux/kasan.h:217 [inline]
 slab_post_alloc_hook+0x53/0x2c0 mm/slab.h:550
 slab_alloc_node mm/slub.c:3240 [inline]
 slab_alloc mm/slub.c:3248 [inline]
 kmem_cache_alloc+0xf5/0x200 mm/slub.c:3253
 skb_clone+0x1d1/0x360 net/core/skbuff.c:1547
 sk_psock_verdict_recv+0x53/0x840 net/core/skmsg.c:1182
 unix_read_sock+0x132/0x370 net/unix/af_unix.c:2431
 sk_psock_verdict_data_ready+0x147/0x1a0 net/core/skmsg.c:1225
 unix_dgram_sendmsg+0x15fa/0x2090 net/unix/af_unix.c:1947
 sock_sendmsg_nosec net/socket.c:704 [inline]
 __sock_sendmsg net/socket.c:716 [inline]
 ____sys_sendmsg+0x59e/0x8f0 net/socket.c:2431
 ___sys_sendmsg+0x252/0x2e0 net/socket.c:2485
 __sys_sendmmsg+0x2bf/0x530 net/socket.c:2571
 __do_sys_sendmmsg net/socket.c:2600 [inline]
 __se_sys_sendmmsg net/socket.c:2597 [inline]
 __x64_sys_sendmmsg+0xa0/0xb0 net/socket.c:2597
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x61/0xcb

Freed by task 39:
 kasan_save_stack mm/kasan/common.c:38 [inline]
 kasan_set_track+0x4b/0x70 mm/kasan/common.c:45
 kasan_set_free_info+0x23/0x40 mm/kasan/generic.c:370
 ____kasan_slab_free+0x126/0x160 mm/kasan/common.c:365
 __kasan_slab_free+0x11/0x20 mm/kasan/common.c:373
 kasan_slab_free include/linux/kasan.h:193 [inline]
 slab_free_hook mm/slub.c:1723 [inline]
 slab_free_freelist_hook+0xbd/0x190 mm/slub.c:1749
 slab_free mm/slub.c:3519 [inline]
 kmem_cache_free+0x116/0x2e0 mm/slub.c:3535
 kfree_skbmem+0x104/0x170
 __kfree_skb net/core/skbuff.c:758 [inline]
 kfree_skb_reason net/core/skbuff.c:778 [inline]
 kfree_skb+0xc2/0x360 net/core/skbuff.c:792
 sock_drop include/linux/skmsg.h:312 [inline]
 sk_psock_backlog+0xc21/0xd90 net/core/skmsg.c:681
 process_one_work+0x6bb/0xc10 kernel/workqueue.c:2325
 worker_thread+0xad5/0x12a0 kernel/workqueue.c:2472
 kthread+0x421/0x510 kernel/kthread.c:337
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:298

The buggy address belongs to the object at ffff88811c0b7780
 which belongs to the cache skbuff_head_cache of size 248
The buggy address is located 236 bytes inside of
 248-byte region [ffff88811c0b7780, ffff88811c0b7878)
The buggy address belongs to the page:
page:ffffea0004702dc0 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x11c0b7
flags: 0x4000000000000200(slab|zone=1)
raw: 4000000000000200 0000000000000000 dead000000000122 ffff888107f99380
raw: 0000000000000000 00000000000c000c 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Unmovable, gfp_mask 0x112a20(GFP_ATOMIC|__GFP_NOWARN|__GFP_NORETRY|__GFP_HARDWALL), pid 60, ts 28641206796, free_ts 27782886599
 set_page_owner include/linux/page_owner.h:33 [inline]
 post_alloc_hook+0x1a3/0x1b0 mm/page_alloc.c:2604
 prep_new_page+0x1b/0x110 mm/page_alloc.c:2610
 get_page_from_freelist+0x3550/0x35d0 mm/page_alloc.c:4484
 __alloc_pages+0x27e/0x8f0 mm/page_alloc.c:5776
 allocate_slab mm/slub.c:1932 [inline]
 new_slab+0x9a/0x4e0 mm/slub.c:1995
 ___slab_alloc+0x39e/0x830 mm/slub.c:3028
 __slab_alloc+0x4a/0x90 mm/slub.c:3115
 slab_alloc_node mm/slub.c:3206 [inline]
 slab_alloc mm/slub.c:3248 [inline]
 kmem_cache_alloc+0x134/0x200 mm/slub.c:3253
 kmem_cache_alloc_node include/linux/slab.h:474 [inline]
 __alloc_skb+0xbe/0x550 net/core/skbuff.c:416
 alloc_skb include/linux/skbuff.h:1183 [inline]
 ndisc_alloc_skb+0xf3/0x2d0 net/ipv6/ndisc.c:421
 ndisc_send_ns+0x29d/0x830 net/ipv6/ndisc.c:627
 addrconf_dad_work+0xb29/0x1710 net/ipv6/addrconf.c:4204
 process_one_work+0x6bb/0xc10 kernel/workqueue.c:2325
 worker_thread+0xad5/0x12a0 kernel/workqueue.c:2472
 kthread+0x421/0x510 kernel/kthread.c:337
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:298
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:26 [inline]
 free_pages_prepare mm/page_alloc.c:1471 [inline]
 free_pcp_prepare mm/page_alloc.c:1543 [inline]
 free_unref_page_prepare+0x7c8/0x7d0 mm/page_alloc.c:3533
 free_unref_page+0xe8/0x750 mm/page_alloc.c:3615
 free_the_page mm/page_alloc.c:804 [inline]
 __free_pages+0x61/0xf0 mm/page_alloc.c:5852
 free_pages+0x7c/0x90 mm/page_alloc.c:5863
 kasan_depopulate_vmalloc_pte+0x6a/0x90 mm/kasan/shadow.c:354
 apply_to_pte_range mm/memory.c:2610 [inline]
 apply_to_pmd_range mm/memory.c:2654 [inline]
 apply_to_pud_range mm/memory.c:2690 [inline]
 apply_to_p4d_range mm/memory.c:2726 [inline]
 __apply_to_page_range+0x8dd/0xbe0 mm/memory.c:2760
 apply_to_existing_page_range+0x38/0x50 mm/memory.c:2793
 kasan_release_vmalloc+0x9a/0xb0 mm/kasan/shadow.c:464
 __purge_vmap_area_lazy+0x154a/0x1690 mm/vmalloc.c:1715
 _vm_unmap_aliases+0x339/0x3b0 mm/vmalloc.c:2118
 vm_unmap_aliases+0x19/0x20 mm/vmalloc.c:2141
 change_page_attr_set_clr+0x308/0x1050 arch/x86/mm/pat/set_memory.c:1740
 change_page_attr_clear arch/x86/mm/pat/set_memory.c:1797 [inline]
 set_memory_ro+0xa1/0xe0 arch/x86/mm/pat/set_memory.c:1943
 bpf_jit_binary_lock_ro include/linux/filter.h:888 [inline]
 bpf_int_jit_compile+0xbf42/0xc6d0 arch/x86/net/bpf_jit_comp.c:2372
 bpf_prog_select_runtime+0x706/0x9e0 kernel/bpf/core.c:1930
 bpf_prog_load+0x1315/0x1b50 kernel/bpf/syscall.c:2337

Memory state around the buggy address:
 ffff88811c0b7700: fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc fc
 ffff88811c0b7780: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88811c0b7800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fc
                                                          ^
 ffff88811c0b7880: fc fc fc fc fc fc fc fc fa fb fb fb fb fb fb fb
 ffff88811c0b7900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
==================================================================
BUG: KASAN: double-free or invalid-free in slab_free mm/slub.c:3519 [inline]
BUG: KASAN: double-free or invalid-free in kmem_cache_free+0x116/0x2e0 mm/slub.c:3535

CPU: 1 PID: 345 Comm: syz-executor.0 Tainted: G    B             5.15.149-syzkaller-1069274-g85445b5a2107 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/02/2024
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x151/0x1b7 lib/dump_stack.c:106
 print_address_description+0x87/0x3b0 mm/kasan/report.c:248
 kasan_report_invalid_free+0x6b/0xa0 mm/kasan/report.c:370
 ____kasan_slab_free+0x13e/0x160
 __kasan_slab_free+0x11/0x20 mm/kasan/common.c:373
 kasan_slab_free include/linux/kasan.h:193 [inline]
 slab_free_hook mm/slub.c:1723 [inline]
 slab_free_freelist_hook+0xbd/0x190 mm/slub.c:1749
 slab_free mm/slub.c:3519 [inline]
 kmem_cache_free+0x116/0x2e0 mm/slub.c:3535
 kfree_skbmem+0x104/0x170
 __kfree_skb net/core/skbuff.c:758 [inline]
 consume_skb+0xb4/0x250 net/core/skbuff.c:930
 __sk_msg_free+0x2dd/0x370 net/core/skmsg.c:205
 sk_msg_free net/core/skmsg.c:218 [inline]
 __sk_psock_purge_ingress_msg net/core/skmsg.c:768 [inline]
 __sk_psock_zap_ingress net/core/skmsg.c:786 [inline]
 sk_psock_stop+0x44c/0x4d0 net/core/skmsg.c:804
 sock_map_close+0x2b9/0x4c0 net/core/sock_map.c:1548
 unix_release+0x82/0xc0 net/unix/af_unix.c:949
 __sock_release net/socket.c:649 [inline]
 sock_close+0xdf/0x270 net/socket.c:1336
 __fput+0x3fe/0x910 fs/file_table.c:280
 ____fput+0x15/0x20 fs/file_table.c:308
 task_work_run+0x129/0x190 kernel/task_work.c:164
 tracehook_notify_resume include/linux/tracehook.h:189 [inline]
 exit_to_user_mode_loop+0xc4/0xe0 kernel/entry/common.c:175
 exit_to_user_mode_prepare+0x5a/0xa0 kernel/entry/common.c:208
 __syscall_exit_to_user_mode_work kernel/entry/common.c:290 [inline]
 syscall_exit_to_user_mode+0x26/0x160 kernel/entry/common.c:301
 do_syscall_64+0x49/0xb0 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x61/0xcb
RIP: 0033:0x7f914cec4c9a
Code: 48 3d 00 f0 ff ff 77 48 c3 0f 1f 80 00 00 00 00 48 83 ec 18 89 7c 24 0c e8 03 7f 02 00 8b 7c 24 0c 89 c2 b8 03 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 36 89 d7 89 44 24 0c e8 63 7f 02 00 8b 44 24
RSP: 002b:00007ffe2eddc870 EFLAGS: 00000293 ORIG_RAX: 0000000000000003
RAX: 0000000000000000 RBX: 0000000000000004 RCX: 00007f914cec4c9a
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000003
RBP: 0000000000000032 R08: 0000001b30a60000 R09: 00007f914cff4f8c
R10: 00007ffe2eddc9c0 R11: 0000000000000293 R12: 00007f914ca4a1b0
R13: ffffffffffffffff R14: 00007f914ca49000 R15: 0000000000006fd1
 </TASK>

Allocated by task 346:
 kasan_save_stack mm/kasan/common.c:38 [inline]
 kasan_set_track mm/kasan/common.c:45 [inline]
 set_alloc_info mm/kasan/common.c:433 [inline]
 __kasan_slab_alloc+0xb1/0xe0 mm/kasan/common.c:466
 kasan_slab_alloc include/linux/kasan.h:217 [inline]
 slab_post_alloc_hook+0x53/0x2c0 mm/slab.h:550
 slab_alloc_node mm/slub.c:3240 [inline]
 slab_alloc mm/slub.c:3248 [inline]
 kmem_cache_alloc+0xf5/0x200 mm/slub.c:3253
 skb_clone+0x1d1/0x360 net/core/skbuff.c:1547
 sk_psock_verdict_recv+0x53/0x840 net/core/skmsg.c:1182
 unix_read_sock+0x132/0x370 net/unix/af_unix.c:2431
 sk_psock_verdict_data_ready+0x147/0x1a0 net/core/skmsg.c:1225
 unix_dgram_sendmsg+0x15fa/0x2090 net/unix/af_unix.c:1947
 sock_sendmsg_nosec net/socket.c:704 [inline]
 __sock_sendmsg net/socket.c:716 [inline]
 ____sys_sendmsg+0x59e/0x8f0 net/socket.c:2431
 ___sys_sendmsg+0x252/0x2e0 net/socket.c:2485
 __sys_sendmmsg+0x2bf/0x530 net/socket.c:2571
 __do_sys_sendmmsg net/socket.c:2600 [inline]
 __se_sys_sendmmsg net/socket.c:2597 [inline]
 __x64_sys_sendmmsg+0xa0/0xb0 net/socket.c:2597
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x61/0xcb

Freed by task 39:
 kasan_save_stack mm/kasan/common.c:38 [inline]
 kasan_set_track+0x4b/0x70 mm/kasan/common.c:45
 kasan_set_free_info+0x23/0x40 mm/kasan/generic.c:370
 ____kasan_slab_free+0x126/0x160 mm/kasan/common.c:365
 __kasan_slab_free+0x11/0x20 mm/kasan/common.c:373
 kasan_slab_free include/linux/kasan.h:193 [inline]
 slab_free_hook mm/slub.c:1723 [inline]
 slab_free_freelist_hook+0xbd/0x190 mm/slub.c:1749
 slab_free mm/slub.c:3519 [inline]
 kmem_cache_free+0x116/0x2e0 mm/slub.c:3535
 kfree_skbmem+0x104/0x170
 __kfree_skb net/core/skbuff.c:758 [inline]
 kfree_skb_reason net/core/skbuff.c:778 [inline]
 kfree_skb+0xc2/0x360 net/core/skbuff.c:792
 sock_drop include/linux/skmsg.h:312 [inline]
 sk_psock_backlog+0xc21/0xd90 net/core/skmsg.c:681
 process_one_work+0x6bb/0xc10 kernel/workqueue.c:2325
 worker_thread+0xad5/0x12a0 kernel/workqueue.c:2472
 kthread+0x421/0x510 kernel/kthread.c:337
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:298

The buggy address belongs to the object at ffff88811c0b7780
 which belongs to the cache skbuff_head_cache of size 248
The buggy address is located 0 bytes inside of
 248-byte region [ffff88811c0b7780, ffff88811c0b7878)
The buggy address belongs to the page:
page:ffffea0004702dc0 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x11c0b7
flags: 0x4000000000000200(slab|zone=1)
raw: 4000000000000200 0000000000000000 dead000000000122 ffff888107f99380
raw: 0000000000000000 00000000000c000c 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Unmovable, gfp_mask 0x112a20(GFP_ATOMIC|__GFP_NOWARN|__GFP_NORETRY|__GFP_HARDWALL), pid 60, ts 28641206796, free_ts 27782886599
 set_page_owner include/linux/page_owner.h:33 [inline]
 post_alloc_hook+0x1a3/0x1b0 mm/page_alloc.c:2604
 prep_new_page+0x1b/0x110 mm/page_alloc.c:2610
 get_page_from_freelist+0x3550/0x35d0 mm/page_alloc.c:4484
 __alloc_pages+0x27e/0x8f0 mm/page_alloc.c:5776
 allocate_slab mm/slub.c:1932 [inline]
 new_slab+0x9a/0x4e0 mm/slub.c:1995
 ___slab_alloc+0x39e/0x830 mm/slub.c:3028
 __slab_alloc+0x4a/0x90 mm/slub.c:3115
 slab_alloc_node mm/slub.c:3206 [inline]
 slab_alloc mm/slub.c:3248 [inline]
 kmem_cache_alloc+0x134/0x200 mm/slub.c:3253
 kmem_cache_alloc_node include/linux/slab.h:474 [inline]
 __alloc_skb+0xbe/0x550 net/core/skbuff.c:416
 alloc_skb include/linux/skbuff.h:1183 [inline]
 ndisc_alloc_skb+0xf3/0x2d0 net/ipv6/ndisc.c:421
 ndisc_send_ns+0x29d/0x830 net/ipv6/ndisc.c:627
 addrconf_dad_work+0xb29/0x1710 net/ipv6/addrconf.c:4204
 process_one_work+0x6bb/0xc10 kernel/workqueue.c:2325
 worker_thread+0xad5/0x12a0 kernel/workqueue.c:2472
 kthread+0x421/0x510 kernel/kthread.c:337
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:298
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:26 [inline]
 free_pages_prepare mm/page_alloc.c:1471 [inline]
 free_pcp_prepare mm/page_alloc.c:1543 [inline]
 free_unref_page_prepare+0x7c8/0x7d0 mm/page_alloc.c:3533
 free_unref_page+0xe8/0x750 mm/page_alloc.c:3615
 free_the_page mm/page_alloc.c:804 [inline]
 __free_pages+0x61/0xf0 mm/page_alloc.c:5852
 free_pages+0x7c/0x90 mm/page_alloc.c:5863
 kasan_depopulate_vmalloc_pte+0x6a/0x90 mm/kasan/shadow.c:354
 apply_to_pte_range mm/memory.c:2610 [inline]
 apply_to_pmd_range mm/memory.c:2654 [inline]
 apply_to_pud_range mm/memory.c:2690 [inline]
 apply_to_p4d_range mm/memory.c:2726 [inline]
 __apply_to_page_range+0x8dd/0xbe0 mm/memory.c:2760
 apply_to_existing_page_range+0x38/0x50 mm/memory.c:2793
 kasan_release_vmalloc+0x9a/0xb0 mm/kasan/shadow.c:464
 __purge_vmap_area_lazy+0x154a/0x1690 mm/vmalloc.c:1715
 _vm_unmap_aliases+0x339/0x3b0 mm/vmalloc.c:2118
 vm_unmap_aliases+0x19/0x20 mm/vmalloc.c:2141
 change_page_attr_set_clr+0x308/0x1050 arch/x86/mm/pat/set_memory.c:1740
 change_page_attr_clear arch/x86/mm/pat/set_memory.c:1797 [inline]
 set_memory_ro+0xa1/0xe0 arch/x86/mm/pat/set_memory.c:1943
 bpf_jit_binary_lock_ro include/linux/filter.h:888 [inline]
 bpf_int_jit_compile+0xbf42/0xc6d0 arch/x86/net/bpf_jit_comp.c:2372
 bpf_prog_select_runtime+0x706/0x9e0 kernel/bpf/core.c:1930
 bpf_prog_load+0x1315/0x1b50 kernel/bpf/syscall.c:2337

Memory state around the buggy address:
 ffff88811c0b7680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88811c0b7700: fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc fc
>ffff88811c0b7780: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                   ^
 ffff88811c0b7800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fc
 ffff88811c0b7880: fc fc fc fc fc fc fc fc fa fb fb fb fb fb fb fb
==================================================================