[Android 5.15] KASAN: slab-out-of-bounds Read in tc_setup_flow_action

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: af461d0249a8 Merge a08241812f21 ("mm: unconditionally clos..
git tree: android13-5.15-lts
console+strace: https://syzkaller.appspot.com/x/log.txt?x=17c7f1c4580000
kernel config: https://syzkaller.appspot.com/x/.config?x=f0e2420ad44d4165
dashboard link: https://syzkaller.appspot.com/bug?extid=04a3bfe287000b1a5529
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=135778b0580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=11ca2edf980000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/1960a4f172c5/disk-af461d02.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/e5307f154ab4/vmlinux-af461d02.xz
kernel image: https://storage.googleapis.com/syzbot-assets/25bda7a9cba0/bzImage-af461d02.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+04a3bf...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: slab-out-of-bounds in is_tcf_tunnel_set include/net/tc_act/tc_tunnel_key.h:33 [inline]
BUG: KASAN: slab-out-of-bounds in tc_setup_flow_action+0xb9d/0x3430 net/sched/cls_api.c:3625
Read of size 8 at addr ffff88810cca5ac0 by task syz-executor185/293

CPU: 0 PID: 293 Comm: syz-executor185 Not tainted 5.15.173-syzkaller-00213-gaf461d0249a8 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
Call Trace:
<TASK>
__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
__asan_report_load8_noabort+0x14/0x20 mm/kasan/report_generic.c:309
is_tcf_tunnel_set include/net/tc_act/tc_tunnel_key.h:33 [inline]
tc_setup_flow_action+0xb9d/0x3430 net/sched/cls_api.c:3625
mall_replace_hw_filter+0x394/0xc20 net/sched/cls_matchall.c:100
mall_change+0x56e/0x780 net/sched/cls_matchall.c:235
tc_new_tfilter+0x151a/0x1c00 net/sched/cls_api.c:2131
rtnetlink_rcv_msg+0x776/0xc40 net/core/rtnetlink.c:5638
netlink_rcv_skb+0x1cf/0x410 net/netlink/af_netlink.c:2493
rtnetlink_rcv+0x1c/0x20 net/core/rtnetlink.c:5665
netlink_unicast_kernel net/netlink/af_netlink.c:1315 [inline]
netlink_unicast+0x8df/0xac0 net/netlink/af_netlink.c:1341
netlink_sendmsg+0xa0a/0xd20 net/netlink/af_netlink.c:1909
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
RIP: 0033:0x7f00bd314829
Code: 48 83 c4 28 c3 e8 37 17 00 00 0f 1f 80 00 00 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 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffd1935a378 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007ffd1935a548 RCX: 00007f00bd314829
RDX: 0000000000000000 RSI: 0000000020000580 RDI: 0000000000000003
RBP: 00007f00bd387610 R08: 0000000000000001 R09: 00007ffd1935a548
R10: 0000000000000009 R11: 0000000000000246 R12: 0000000000000001
R13: 00007ffd1935a538 R14: 0000000000000001 R15: 0000000000000001
</TASK>

Allocated by task 293:
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_kmalloc+0xdb/0x110 mm/kasan/common.c:512
__kasan_kmalloc+0x9/0x10 mm/kasan/common.c:521
kasan_kmalloc include/linux/kasan.h:227 [inline]
__kmalloc+0x13f/0x2c0 mm/slub.c:4431
kmalloc include/linux/slab.h:608 [inline]
kzalloc include/linux/slab.h:733 [inline]
tcf_idr_create+0x5f/0x780 net/sched/act_api.c:478
tcf_idr_create_from_flags+0x5f/0x70 net/sched/act_api.c:536
tcf_gact_init+0x3cd/0x6e0 net/sched/act_gact.c:102
tcf_action_init_1+0x50f/0x7f0 net/sched/act_api.c:1071
tcf_action_init+0x306/0x840 net/sched/act_api.c:1130
tcf_exts_validate+0x236/0x520 net/sched/cls_api.c:3073
mall_set_parms+0x44/0x4b0 net/sched/cls_matchall.c:171
mall_change+0x495/0x780 net/sched/cls_matchall.c:229
tc_new_tfilter+0x151a/0x1c00 net/sched/cls_api.c:2131
rtnetlink_rcv_msg+0x776/0xc40 net/core/rtnetlink.c:5638
netlink_rcv_skb+0x1cf/0x410 net/netlink/af_netlink.c:2493
rtnetlink_rcv+0x1c/0x20 net/core/rtnetlink.c:5665
netlink_unicast_kernel net/netlink/af_netlink.c:1315 [inline]
netlink_unicast+0x8df/0xac0 net/netlink/af_netlink.c:1341
netlink_sendmsg+0xa0a/0xd20 net/netlink/af_netlink.c:1909
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

The buggy address belongs to the object at ffff88810cca5a00
which belongs to the cache kmalloc-192 of size 192
The buggy address is located 0 bytes to the right of
192-byte region [ffff88810cca5a00, ffff88810cca5ac0)
The buggy address belongs to the page:
page:ffffea0004332940 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x10cca5
flags: 0x4000000000000200(slab|zone=1)
raw: 4000000000000200 ffffea000431b180 0000000c0000000c ffff888100042c00
raw: 0000000000000000 0000000080100010 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 0x12cc0(GFP_KERNEL|__GFP_NOWARN|__GFP_NORETRY), pid 71, ts 3972592918, free_ts 3972420148
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_trace+0x147/0x270 mm/slub.c:3267
kmalloc include/linux/slab.h:603 [inline]
kzalloc include/linux/slab.h:733 [inline]
alloc_fs_context+0x65/0x830 fs/fs_context.c:257
fs_context_for_mount+0x24/0x30 fs/fs_context.c:304
do_new_mount+0x15c/0xb30 fs/namespace.c:2991
path_mount+0x671/0x1070 fs/namespace.c:3342
do_mount fs/namespace.c:3355 [inline]
__do_sys_mount fs/namespace.c:3563 [inline]
__se_sys_mount+0x2c4/0x3b0 fs/namespace.c:3540
__x64_sys_mount+0xbf/0xd0 fs/namespace.c:3540
x64_sys_call+0x49d/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:166
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
free_the_page mm/page_alloc.c:805 [inline]
__free_pages+0x61/0xf0 mm/page_alloc.c:5856
free_pages+0x7c/0x90 mm/page_alloc.c:5867
selinux_genfs_get_sid+0x24d/0x2a0 security/selinux/hooks.c:1375
inode_doinit_with_dentry+0x8d2/0x1070 security/selinux/hooks.c:1570
selinux_d_instantiate+0x27/0x40 security/selinux/hooks.c:6489
security_d_instantiate+0x9f/0x100 security/security.c:2074
d_splice_alias+0x6d/0x390 fs/dcache.c:3071
kernfs_iop_lookup+0x29e/0x2f0 fs/kernfs/dir.c:1175
__lookup_slow+0x2b9/0x400 fs/namei.c:1663
lookup_slow+0x5a/0x80 fs/namei.c:1680
walk_component+0x48c/0x610 fs/namei.c:1976
lookup_last fs/namei.c:2431 [inline]
path_lookupat+0x16d/0x450 fs/namei.c:2455
filename_lookup+0x230/0x5c0 fs/namei.c:2484
user_path_at_empty+0x43/0x1a0 fs/namei.c:2883

Memory state around the buggy address:
ffff88810cca5980: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
ffff88810cca5a00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff88810cca5a80: 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc
^
ffff88810cca5b00: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88810cca5b80: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
==================================================================


---
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[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 49e8ba0a684f Merge 5.10.232 into android13-5.10-lts
git tree: android13-5.10-lts
console+strace: https://syzkaller.appspot.com/x/log.txt?x=17aa2edf980000
kernel config: https://syzkaller.appspot.com/x/.config?x=bbadaa04d97ea184
dashboard link: https://syzkaller.appspot.com/bug?extid=7a1c3b8c6950bb246cfc

compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=106a2edf980000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=143778b0580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/dc246d2f5085/disk-49e8ba0a.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/315e306cbeb3/vmlinux-49e8ba0a.xz
kernel image: https://storage.googleapis.com/syzbot-assets/fa96edea9db9/bzImage-49e8ba0a.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:

Reported-by: syzbot+7a1c3b...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: slab-out-of-bounds in is_tcf_tunnel_set include/net/tc_act/tc_tunnel_key.h:33 [inline]

BUG: KASAN: slab-out-of-bounds in tc_setup_flow_action+0xbb8/0x3630 net/sched/cls_api.c:3639
Read of size 8 at addr ffff88810c91cac0 by task syz-executor335/287

CPU: 0 PID: 287 Comm: syz-executor335 Not tainted 5.10.232-syzkaller-00746-g49e8ba0a684f #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
Call Trace:

__dump_stack lib/dump_stack.c:77 [inline]
dump_stack_lvl+0x1e2/0x24b lib/dump_stack.c:118
print_address_description+0x81/0x3b0 mm/kasan/report.c:248
__kasan_report mm/kasan/report.c:435 [inline]
kasan_report+0x179/0x1c0 mm/kasan/report.c:452

__asan_report_load8_noabort+0x14/0x20 mm/kasan/report_generic.c:309
is_tcf_tunnel_set include/net/tc_act/tc_tunnel_key.h:33 [inline]

tc_setup_flow_action+0xbb8/0x3630 net/sched/cls_api.c:3639
mall_replace_hw_filter+0x394/0xc10 net/sched/cls_matchall.c:100
mall_change+0x573/0x7a0 net/sched/cls_matchall.c:236
tc_new_tfilter+0x168e/0x1dc0 net/sched/cls_api.c:2134
rtnetlink_rcv_msg+0x77a/0xc50 net/core/rtnetlink.c:5598
netlink_rcv_skb+0x1cf/0x410 net/netlink/af_netlink.c:2485
rtnetlink_rcv+0x1c/0x20 net/core/rtnetlink.c:5625
netlink_unicast_kernel net/netlink/af_netlink.c:1307 [inline]
netlink_unicast+0x8df/0xac0 net/netlink/af_netlink.c:1333
netlink_sendmsg+0xa46/0xd00 net/netlink/af_netlink.c:1901
sock_sendmsg_nosec net/socket.c:652 [inline]
__sock_sendmsg net/socket.c:664 [inline]
____sys_sendmsg+0x59e/0x8f0 net/socket.c:2376
___sys_sendmsg+0x252/0x2e0 net/socket.c:2430
__sys_sendmsg net/socket.c:2459 [inline]
__do_sys_sendmsg net/socket.c:2468 [inline]
__se_sys_sendmsg+0x1b1/0x280 net/socket.c:2466
__x64_sys_sendmsg+0x7b/0x90 net/socket.c:2466
do_syscall_64+0x34/0x70
entry_SYSCALL_64_after_hwframe+0x61/0xcb
RIP: 0033:0x7f81e7aae829

Code: 48 83 c4 28 c3 e8 37 17 00 00 0f 1f 80 00 00 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 b8 ff ff ff f7 d8 64 89 01 48

RSP: 002b:00007ffe5e4decb8 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007ffe5e4dee88 RCX: 00007f81e7aae829

RDX: 0000000000000000 RSI: 0000000020000580 RDI: 0000000000000003

RBP: 00007f81e7b21610 R08: 0000000000000001 R09: 00007ffe5e4dee88

R10: 0000000000000009 R11: 0000000000000246 R12: 0000000000000001

R13: 00007ffe5e4dee78 R14: 0000000000000001 R15: 0000000000000001

Allocated by task 287:

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:430 [inline]
____kasan_kmalloc+0xdb/0x110 mm/kasan/common.c:509
__kasan_kmalloc+0x9/0x10 mm/kasan/common.c:518
kasan_kmalloc include/linux/kasan.h:254 [inline]
__kmalloc+0x1aa/0x330 mm/slub.c:4033
kmalloc include/linux/slab.h:557 [inline]
kzalloc include/linux/slab.h:664 [inline]
tcf_idr_create+0x5f/0x770 net/sched/act_api.c:430
tcf_idr_create_from_flags+0x5f/0x70 net/sched/act_api.c:488
tcf_gact_init+0x373/0x6e0 net/sched/act_gact.c:102
tcf_action_init_1+0x584/0x830 net/sched/act_api.c:1052
tcf_action_init+0x2b5/0x800 net/sched/act_api.c:1109
tcf_exts_validate+0x232/0x540 net/sched/cls_api.c:3086
mall_set_parms+0x4b/0x440 net/sched/cls_matchall.c:171
mall_change+0x49e/0x7a0 net/sched/cls_matchall.c:230
tc_new_tfilter+0x168e/0x1dc0 net/sched/cls_api.c:2134
rtnetlink_rcv_msg+0x77a/0xc50 net/core/rtnetlink.c:5598
netlink_rcv_skb+0x1cf/0x410 net/netlink/af_netlink.c:2485
rtnetlink_rcv+0x1c/0x20 net/core/rtnetlink.c:5625
netlink_unicast_kernel net/netlink/af_netlink.c:1307 [inline]
netlink_unicast+0x8df/0xac0 net/netlink/af_netlink.c:1333
netlink_sendmsg+0xa46/0xd00 net/netlink/af_netlink.c:1901
sock_sendmsg_nosec net/socket.c:652 [inline]
__sock_sendmsg net/socket.c:664 [inline]
____sys_sendmsg+0x59e/0x8f0 net/socket.c:2376
___sys_sendmsg+0x252/0x2e0 net/socket.c:2430
__sys_sendmsg net/socket.c:2459 [inline]
__do_sys_sendmsg net/socket.c:2468 [inline]
__se_sys_sendmsg+0x1b1/0x280 net/socket.c:2466
__x64_sys_sendmsg+0x7b/0x90 net/socket.c:2466
do_syscall_64+0x34/0x70
entry_SYSCALL_64_after_hwframe+0x61/0xcb

The buggy address belongs to the object at ffff88810c91ca00

which belongs to the cache kmalloc-192 of size 192
The buggy address is located 0 bytes to the right of

192-byte region [ffff88810c91ca00, ffff88810c91cac0)

The buggy address belongs to the page:

page:ffffea0004324700 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x10c91c
flags: 0x4000000000000200(slab)
raw: 4000000000000200 ffffea0004324a00 0000000200000002 ffff888100043380

raw: 0000000000000000 0000000080100010 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 0x12cc0(GFP_KERNEL|__GFP_NOWARN|__GFP_NORETRY), pid 65, ts 3184401735, free_ts 3179469715
set_page_owner include/linux/page_owner.h:35 [inline]
post_alloc_hook mm/page_alloc.c:2456 [inline]
prep_new_page+0x166/0x180 mm/page_alloc.c:2462
get_page_from_freelist+0x2d8c/0x2f30 mm/page_alloc.c:4254
__alloc_pages_nodemask+0x435/0xaf0 mm/page_alloc.c:5348
allocate_slab mm/slub.c:1808 [inline]
new_slab+0x80/0x400 mm/slub.c:1869
new_slab_objects mm/slub.c:2627 [inline]
___slab_alloc+0x302/0x4b0 mm/slub.c:2791
__slab_alloc+0x63/0xa0 mm/slub.c:2831
slab_alloc_node mm/slub.c:2913 [inline]
slab_alloc mm/slub.c:2955 [inline]
kmem_cache_alloc_trace+0x1bd/0x2e0 mm/slub.c:2972
kmalloc include/linux/slab.h:552 [inline]
kzalloc include/linux/slab.h:664 [inline]
shmem_fill_super+0x78/0xb50 mm/shmem.c:3708
vfs_get_super fs/super.c:1214 [inline]
get_tree_nodev+0xb2/0x160 fs/super.c:1244
shmem_get_tree+0x1c/0x20 mm/shmem.c:3788
vfs_get_tree+0x88/0x290 fs/super.c:1572
do_new_mount+0x2ba/0xb30 fs/namespace.c:2917
path_mount+0x56f/0xcb0 fs/namespace.c:3247
do_mount fs/namespace.c:3260 [inline]
__do_sys_mount fs/namespace.c:3468 [inline]
__se_sys_mount+0x2c4/0x3b0 fs/namespace.c:3445
__x64_sys_mount+0xbf/0xd0 fs/namespace.c:3445
do_syscall_64+0x34/0x70

page last free stack trace:

reset_page_owner include/linux/page_owner.h:28 [inline]
free_pages_prepare mm/page_alloc.c:1349 [inline]
free_pcp_prepare mm/page_alloc.c:1421 [inline]
free_unref_page_prepare+0x2ae/0x2d0 mm/page_alloc.c:3336
free_unref_page_list+0x122/0xb20 mm/page_alloc.c:3443
release_pages+0xea0/0xef0 mm/swap.c:1103
free_pages_and_swap_cache+0x8a/0xa0 mm/swap_state.c:356
tlb_batch_pages_flush mm/mmu_gather.c:49 [inline]
tlb_flush_mmu_free mm/mmu_gather.c:240 [inline]
tlb_flush_mmu mm/mmu_gather.c:247 [inline]
tlb_finish_mmu+0x177/0x320 mm/mmu_gather.c:326
exit_mmap+0x306/0x560 mm/mmap.c:3375
__mmput+0x95/0x2d0 kernel/fork.c:1153
mmput+0x59/0x170 kernel/fork.c:1176
exit_mm kernel/exit.c:539 [inline]
do_exit+0xbda/0x2a50 kernel/exit.c:850
do_group_exit+0x141/0x310 kernel/exit.c:985
__do_sys_exit_group kernel/exit.c:996 [inline]
__se_sys_exit_group kernel/exit.c:994 [inline]
__x64_sys_exit_group+0x3f/0x40 kernel/exit.c:994
do_syscall_64+0x34/0x70
entry_SYSCALL_64_after_hwframe+0x61/0xcb

Memory state around the buggy address:

ffff88810c91c980: 00 00 00 fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88810c91ca00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff88810c91ca80: 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc
^
ffff88810c91cb00: 00 00 00 00 00 00 00 00 00 00 00