==================================================================
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 ffff88811fbae86c by task syz-executor.0/366
CPU: 1 PID: 366 Comm: syz-executor.0 Not tainted 5.15.178-syzkaller-1079147-g7d1f9b5c2ff5 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
Call Trace:
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x151/0x1c0 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:773 [inline]
__sk_psock_zap_ingress net/core/skmsg.c:791 [inline]
sk_psock_stop+0x4e3/0x580 net/core/skmsg.c:809
sk_psock_drop+0x219/0x310 net/core/skmsg.c:848
sk_psock_put include/linux/skmsg.h:463 [inline]
sock_map_unref+0x3c6/0x430 net/core/sock_map.c:184
__sock_map_delete net/core/sock_map.c:426 [inline]
sock_map_delete_from_link net/core/sock_map.c:439 [inline]
sock_map_unlink net/core/sock_map.c:1498 [inline]
sock_map_remove_links+0x41c/0x650 net/core/sock_map.c:1513
sock_map_close+0x114/0x530 net/core/sock_map.c:1550
unix_release+0x82/0xc0 net/unix/af_unix.c:936
__sock_release net/socket.c:649 [inline]
sock_close+0xdf/0x270 net/socket.c:1336
__fput+0x228/0x8c0 fs/file_table.c:280
____fput+0x15/0x20 fs/file_table.c:308
task_work_run+0x129/0x190 kernel/task_work.c:188
tracehook_notify_resume include/linux/tracehook.h:189 [inline]
exit_to_user_mode_loop+0xc4/0xe0 kernel/entry/common.c:181
exit_to_user_mode_prepare+0x5a/0xa0 kernel/entry/common.c:214
__syscall_exit_to_user_mode_work kernel/entry/common.c:296 [inline]
syscall_exit_to_user_mode+0x26/0x160 kernel/entry/common.c:307
do_syscall_64+0x47/0xb0 arch/x86/entry/common.c:86
entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7fc018e24d9a
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:00007ffc3e38d290 EFLAGS: 00000293 ORIG_RAX: 0000000000000003
RAX: 0000000000000000 RBX: 0000000000000004 RCX: 00007fc018e24d9a
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000003
RBP: 00007fc018f55980 R08: 0000001b31f60000 R09: 0000000000000001
R10: 0000000000000001 R11: 0000000000000293 R12: 000000000000c577
R13: 000000000000c238 R14: 00007ffc3e38d450 R15: 00007fc018ddccb0
Allocated by task 367:
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:3250 [inline]
kmem_cache_alloc+0xf5/0x250 mm/slub.c:3255
skb_clone+0x1d1/0x360 net/core/skbuff.c:1547
sk_psock_verdict_recv+0x53/0x840 net/core/skmsg.c:1187
unix_read_sock+0x132/0x370 net/unix/af_unix.c:2428
sk_psock_verdict_data_ready+0x147/0x1a0 net/core/skmsg.c:1230
unix_dgram_sendmsg+0x15fa/0x2090 net/unix/af_unix.c:1942
sock_sendmsg_nosec net/socket.c:704 [inline]
__sock_sendmsg net/socket.c:716 [inline]
____sys_sendmsg+0x59e/0x8f0 net/socket.c:2436
___sys_sendmsg+0x252/0x2e0 net/socket.c:2490
__sys_sendmsg net/socket.c:2519 [inline]
__do_sys_sendmsg net/socket.c:2528 [inline]
__se_sys_sendmsg+0x19a/0x260 net/socket.c:2526
__x64_sys_sendmsg+0x7b/0x90 net/socket.c:2526
x64_sys_call+0x16a/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:47
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0
Freed by task 311:
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:3521 [inline]
kmem_cache_free+0x115/0x330 mm/slub.c:3539
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+0xad1/0xdc0 net/core/skmsg.c:684
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:287
The buggy address belongs to the object at ffff88811fbae780
which belongs to the cache skbuff_head_cache of size 248
The buggy address is located 236 bytes inside of
248-byte region [ffff88811fbae780, ffff88811fbae878)
The buggy address belongs to the page:
page:ffffea00047eeb80 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x11fbae
flags: 0x4000000000000200(slab|zone=1)
raw: 4000000000000200 0000000000000000 dead000000000122 ffff8881081ab080
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 0x112cc0(GFP_USER|__GFP_NOWARN|__GFP_NORETRY), pid 90, ts 49703833839, free_ts 42441259919
set_page_owner include/linux/page_owner.h:33 [inline]
post_alloc_hook+0x1a3/0x1b0 mm/page_alloc.c:2605
prep_new_page+0x1b/0x110 mm/page_alloc.c:2611
get_page_from_freelist+0x3550/0x35d0 mm/page_alloc.c:4485
__alloc_pages+0x27e/0x8f0 mm/page_alloc.c:5780
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:3250 [inline]
kmem_cache_alloc+0x139/0x250 mm/slub.c:3255
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]
alloc_skb_with_frags+0xa6/0x680 net/core/skbuff.c:6194
sock_alloc_send_pskb+0x915/0xa50 net/core/sock.c:2539
unix_dgram_sendmsg+0x6fd/0x2090 net/unix/af_unix.c:1805
sock_sendmsg_nosec net/socket.c:704 [inline]
__sock_sendmsg net/socket.c:716 [inline]
__sys_sendto+0x564/0x720 net/socket.c:2063
__do_sys_sendto net/socket.c:2075 [inline]
__se_sys_sendto net/socket.c:2071 [inline]
__x64_sys_sendto+0xe5/0x100 net/socket.c:2071
x64_sys_call+0x15c/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:45
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:80
page last free stack trace:
reset_page_owner include/linux/page_owner.h:26 [inline]
free_pages_prepare mm/page_alloc.c:1472 [inline]
free_pcp_prepare mm/page_alloc.c:1544 [inline]
free_unref_page_prepare+0x7c8/0x7d0 mm/page_alloc.c:3534
free_unref_page+0xe8/0x750 mm/page_alloc.c:3616
__put_single_page mm/swap.c:98 [inline]
__put_page+0xb0/0xe0 mm/swap.c:129
put_page include/linux/mm.h:1295 [inline]
anon_pipe_buf_release+0x187/0x200 fs/pipe.c:137
pipe_buf_release include/linux/pipe_fs_i.h:219 [inline]
pipe_read+0x5a6/0x1040 fs/pipe.c:323
call_read_iter include/linux/fs.h:2200 [inline]
new_sync_read fs/read_write.c:404 [inline]
vfs_read+0xa81/0xd40 fs/read_write.c:485
ksys_read+0x199/0x2c0 fs/read_write.c:623
__do_sys_read fs/read_write.c:633 [inline]
__se_sys_read fs/read_write.c:631 [inline]
__x64_sys_read+0x7b/0x90 fs/read_write.c:631
x64_sys_call+0x28/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:1
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0
Memory state around the buggy address:
ffff88811fbae700: fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc fc
ffff88811fbae780: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88811fbae800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fc
^
ffff88811fbae880: fc fc fc fc fc fc fc fc fa fb fb fb fb fb fb fb
ffff88811fbae900: 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:3521 [inline]
BUG: KASAN: double-free or invalid-free in kmem_cache_free+0x115/0x330 mm/slub.c:3539
CPU: 1 PID: 366 Comm: syz-executor.0 Tainted: G B 5.15.178-syzkaller-1079147-g7d1f9b5c2ff5 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
Call Trace:
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x151/0x1c0 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:3521 [inline]
kmem_cache_free+0x115/0x330 mm/slub.c:3539
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:773 [inline]
__sk_psock_zap_ingress net/core/skmsg.c:791 [inline]
sk_psock_stop+0x4e3/0x580 net/core/skmsg.c:809
sk_psock_drop+0x219/0x310 net/core/skmsg.c:848
sk_psock_put include/linux/skmsg.h:463 [inline]
sock_map_unref+0x3c6/0x430 net/core/sock_map.c:184
__sock_map_delete net/core/sock_map.c:426 [inline]
sock_map_delete_from_link net/core/sock_map.c:439 [inline]
sock_map_unlink net/core/sock_map.c:1498 [inline]
sock_map_remove_links+0x41c/0x650 net/core/sock_map.c:1513
sock_map_close+0x114/0x530 net/core/sock_map.c:1550
unix_release+0x82/0xc0 net/unix/af_unix.c:936
__sock_release net/socket.c:649 [inline]
sock_close+0xdf/0x270 net/socket.c:1336
__fput+0x228/0x8c0 fs/file_table.c:280
____fput+0x15/0x20 fs/file_table.c:308
task_work_run+0x129/0x190 kernel/task_work.c:188
tracehook_notify_resume include/linux/tracehook.h:189 [inline]
exit_to_user_mode_loop+0xc4/0xe0 kernel/entry/common.c:181
exit_to_user_mode_prepare+0x5a/0xa0 kernel/entry/common.c:214
__syscall_exit_to_user_mode_work kernel/entry/common.c:296 [inline]
syscall_exit_to_user_mode+0x26/0x160 kernel/entry/common.c:307
do_syscall_64+0x47/0xb0 arch/x86/entry/common.c:86
entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7fc018e24d9a
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:00007ffc3e38d290 EFLAGS: 00000293 ORIG_RAX: 0000000000000003
RAX: 0000000000000000 RBX: 0000000000000004 RCX: 00007fc018e24d9a
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000003
RBP: 00007fc018f55980 R08: 0000001b31f60000 R09: 0000000000000001
R10: 0000000000000001 R11: 0000000000000293 R12: 000000000000c577
R13: 000000000000c238 R14: 00007ffc3e38d450 R15: 00007fc018ddccb0
Allocated by task 367:
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:3250 [inline]
kmem_cache_alloc+0xf5/0x250 mm/slub.c:3255
skb_clone+0x1d1/0x360 net/core/skbuff.c:1547
sk_psock_verdict_recv+0x53/0x840 net/core/skmsg.c:1187
unix_read_sock+0x132/0x370 net/unix/af_unix.c:2428
sk_psock_verdict_data_ready+0x147/0x1a0 net/core/skmsg.c:1230
unix_dgram_sendmsg+0x15fa/0x2090 net/unix/af_unix.c:1942
sock_sendmsg_nosec net/socket.c:704 [inline]
__sock_sendmsg net/socket.c:716 [inline]
____sys_sendmsg+0x59e/0x8f0 net/socket.c:2436
___sys_sendmsg+0x252/0x2e0 net/socket.c:2490
__sys_sendmsg net/socket.c:2519 [inline]
__do_sys_sendmsg net/socket.c:2528 [inline]
__se_sys_sendmsg+0x19a/0x260 net/socket.c:2526
__x64_sys_sendmsg+0x7b/0x90 net/socket.c:2526
x64_sys_call+0x16a/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:47
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0
Freed by task 311:
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:3521 [inline]
kmem_cache_free+0x115/0x330 mm/slub.c:3539
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+0xad1/0xdc0 net/core/skmsg.c:684
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:287
The buggy address belongs to the object at ffff88811fbae780
which belongs to the cache skbuff_head_cache of size 248
The buggy address is located 0 bytes inside of
248-byte region [ffff88811fbae780, ffff88811fbae878)
The buggy address belongs to the page:
page:ffffea00047eeb80 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x11fbae
flags: 0x4000000000000200(slab|zone=1)
raw: 4000000000000200 0000000000000000 dead000000000122 ffff8881081ab080
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 0x112cc0(GFP_USER|__GFP_NOWARN|__GFP_NORETRY), pid 90, ts 49703833839, free_ts 42441259919
set_page_owner include/linux/page_owner.h:33 [inline]
post_alloc_hook+0x1a3/0x1b0 mm/page_alloc.c:2605
prep_new_page+0x1b/0x110 mm/page_alloc.c:2611
get_page_from_freelist+0x3550/0x35d0 mm/page_alloc.c:4485
__alloc_pages+0x27e/0x8f0 mm/page_alloc.c:5780
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:3250 [inline]
kmem_cache_alloc+0x139/0x250 mm/slub.c:3255
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]
alloc_skb_with_frags+0xa6/0x680 net/core/skbuff.c:6194
sock_alloc_send_pskb+0x915/0xa50 net/core/sock.c:2539
unix_dgram_sendmsg+0x6fd/0x2090 net/unix/af_unix.c:1805
sock_sendmsg_nosec net/socket.c:704 [inline]
__sock_sendmsg net/socket.c:716 [inline]
__sys_sendto+0x564/0x720 net/socket.c:2063
__do_sys_sendto net/socket.c:2075 [inline]
__se_sys_sendto net/socket.c:2071 [inline]
__x64_sys_sendto+0xe5/0x100 net/socket.c:2071
x64_sys_call+0x15c/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:45
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:80
page last free stack trace:
reset_page_owner include/linux/page_owner.h:26 [inline]
free_pages_prepare mm/page_alloc.c:1472 [inline]
free_pcp_prepare mm/page_alloc.c:1544 [inline]
free_unref_page_prepare+0x7c8/0x7d0 mm/page_alloc.c:3534
free_unref_page+0xe8/0x750 mm/page_alloc.c:3616
__put_single_page mm/swap.c:98 [inline]
__put_page+0xb0/0xe0 mm/swap.c:129
put_page include/linux/mm.h:1295 [inline]
anon_pipe_buf_release+0x187/0x200 fs/pipe.c:137
pipe_buf_release include/linux/pipe_fs_i.h:219 [inline]
pipe_read+0x5a6/0x1040 fs/pipe.c:323
call_read_iter include/linux/fs.h:2200 [inline]
new_sync_read fs/read_write.c:404 [inline]
vfs_read+0xa81/0xd40 fs/read_write.c:485
ksys_read+0x199/0x2c0 fs/read_write.c:623
__do_sys_read fs/read_write.c:633 [inline]
__se_sys_read fs/read_write.c:631 [inline]
__x64_sys_read+0x7b/0x90 fs/read_write.c:631
x64_sys_call+0x28/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:1
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0
Memory state around the buggy address:
ffff88811fbae680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88811fbae700: fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc fc
>ffff88811fbae780: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88811fbae800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fc
ffff88811fbae880: fc fc fc fc fc fc fc fc fa fb fb fb fb fb fb fb
==================================================================