==================================================================
BUG: KASAN: slab-use-after-free in v4l2_fh_init+0x27d/0x2c0 drivers/media/v4l2-core/v4l2-fh.c:25
Read of size 8 at addr ffff88803b578740 by task v4l_id/20102
CPU: 0 UID: 0 PID: 20102 Comm: v4l_id Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
Call Trace:
__dump_stack lib/dump_stack.c:94 [inline]
dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120
print_address_description mm/kasan/report.c:378 [inline]
print_report+0xcd/0x630 mm/kasan/report.c:482
kasan_report+0xe0/0x110 mm/kasan/report.c:595
v4l2_fh_init+0x27d/0x2c0 drivers/media/v4l2-core/v4l2-fh.c:25
v4l2_fh_open+0x64/0xa0 drivers/media/v4l2-core/v4l2-fh.c:64
em28xx_v4l2_open+0x24e/0x7e0 drivers/media/usb/em28xx/em28xx-video.c:2153
v4l2_open+0x1d2/0x5e0 drivers/media/v4l2-core/v4l2-dev.c:433
chrdev_open+0x234/0x6a0 fs/char_dev.c:414
do_dentry_open+0x982/0x1530 fs/open.c:965
vfs_open+0x82/0x3f0 fs/open.c:1097
do_open fs/namei.c:3975 [inline]
path_openat+0x1de4/0x2cb0 fs/namei.c:4134
do_filp_open+0x20b/0x470 fs/namei.c:4161
do_sys_openat2+0x11b/0x1d0 fs/open.c:1437
do_sys_open fs/open.c:1452 [inline]
__do_sys_openat fs/open.c:1468 [inline]
__se_sys_openat fs/open.c:1463 [inline]
__x64_sys_openat+0x174/0x210 fs/open.c:1463
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xcd/0xfa0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f7e57aa7407
Code: 48 89 fa 4c 89 df e8 38 aa 00 00 8b 93 08 03 00 00 59 5e 48 83 f8 fc 74 1a 5b c3 0f 1f 84 00 00 00 00 00 48 8b 44 24 10 0f 05 <5b> c3 0f 1f 80 00 00 00 00 83 e2 39 83 fa 08 75 de e8 23 ff ff ff
RSP: 002b:00007ffd724c9940 EFLAGS: 00000202 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007f7e58225880 RCX: 00007f7e57aa7407
RDX: 0000000000000000 RSI: 00007ffd724c9f1b RDI: ffffffffffffff9c
RBP: 0000000000000002 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000202 R12: 0000000000000000
R13: 00007ffd724c9b90 R14: 00007f7e5838c000 R15: 00005585bbcf74d8
Allocated by task 5905:
kasan_save_stack+0x33/0x60 mm/kasan/common.c:56
kasan_save_track+0x14/0x30 mm/kasan/common.c:77
poison_kmalloc_redzone mm/kasan/common.c:400 [inline]
__kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:417
kmalloc_noprof include/linux/slab.h:957 [inline]
kzalloc_noprof include/linux/slab.h:1094 [inline]
em28xx_v4l2_init+0x114/0x4080 drivers/media/usb/em28xx/em28xx-video.c:2532
em28xx_init_extension+0x13a/0x200 drivers/media/usb/em28xx/em28xx-core.c:1117
request_module_async+0x61/0x70 drivers/media/usb/em28xx/em28xx-cards.c:3457
process_one_work+0x9cf/0x1b70 kernel/workqueue.c:3263
process_scheduled_works kernel/workqueue.c:3346 [inline]
worker_thread+0x6c8/0xf10 kernel/workqueue.c:3427
kthread+0x3c5/0x780 kernel/kthread.c:463
ret_from_fork+0x675/0x7d0 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
Freed by task 5905:
kasan_save_stack+0x33/0x60 mm/kasan/common.c:56
kasan_save_track+0x14/0x30 mm/kasan/common.c:77
__kasan_save_free_info+0x3b/0x60 mm/kasan/generic.c:587
kasan_save_free_info mm/kasan/kasan.h:406 [inline]
poison_slab_object mm/kasan/common.c:252 [inline]
__kasan_slab_free+0x5f/0x80 mm/kasan/common.c:284
kasan_slab_free include/linux/kasan.h:234 [inline]
slab_free_hook mm/slub.c:2530 [inline]
slab_free mm/slub.c:6619 [inline]
kfree+0x2b8/0x6d0 mm/slub.c:6826
em28xx_free_v4l2 drivers/media/usb/em28xx/em28xx-video.c:2118 [inline]
kref_put include/linux/kref.h:65 [inline]
em28xx_v4l2_init+0x22b5/0x4080 drivers/media/usb/em28xx/em28xx-video.c:2901
em28xx_init_extension+0x13a/0x200 drivers/media/usb/em28xx/em28xx-core.c:1117
request_module_async+0x61/0x70 drivers/media/usb/em28xx/em28xx-cards.c:3457
process_one_work+0x9cf/0x1b70 kernel/workqueue.c:3263
process_scheduled_works kernel/workqueue.c:3346 [inline]
worker_thread+0x6c8/0xf10 kernel/workqueue.c:3427
kthread+0x3c5/0x780 kernel/kthread.c:463
ret_from_fork+0x675/0x7d0 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 ffff88803b578000
which belongs to the cache kmalloc-8k of size 8192
The buggy address is located 1856 bytes inside of
freed 8192-byte region [ffff88803b578000, ffff88803b57a000)
The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x3b578
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 ffff88813ffa7280 dead000000000122 0000000000000000
raw: 0000000000000000 0000000080020002 00000000f5000000 0000000000000000
head: 00fff00000000040 ffff88813ffa7280 dead000000000122 0000000000000000
head: 0000000000000000 0000000080020002 00000000f5000000 0000000000000000
head: 00fff00000000003 ffffea0000ed5e01 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 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 5905, tgid 5905 (kworker/0:4), ts 1194903977210, free_ts 1194903743889
set_page_owner include/linux/page_owner.h:32 [inline]
post_alloc_hook+0x1c0/0x230 mm/page_alloc.c:1850
prep_new_page mm/page_alloc.c:1858 [inline]
get_page_from_freelist+0x10a3/0x3a30 mm/page_alloc.c:3884
__alloc_frozen_pages_noprof+0x25f/0x2470 mm/page_alloc.c:5183
alloc_pages_mpol+0x1fb/0x550 mm/mempolicy.c:2416
alloc_slab_page mm/slub.c:3046 [inline]
allocate_slab mm/slub.c:3219 [inline]
new_slab+0x24a/0x360 mm/slub.c:3273
___slab_alloc+0xdc4/0x1ae0 mm/slub.c:4643
__slab_alloc.constprop.0+0x63/0x110 mm/slub.c:4762
__slab_alloc_node mm/slub.c:4838 [inline]
slab_alloc_node mm/slub.c:5260 [inline]
__kmalloc_cache_noprof+0x477/0x780 mm/slub.c:5750
kmalloc_noprof include/linux/slab.h:957 [inline]
kzalloc_noprof include/linux/slab.h:1094 [inline]
em28xx_v4l2_init+0x114/0x4080 drivers/media/usb/em28xx/em28xx-video.c:2532
em28xx_init_extension+0x13a/0x200 drivers/media/usb/em28xx/em28xx-core.c:1117
request_module_async+0x61/0x70 drivers/media/usb/em28xx/em28xx-cards.c:3457
process_one_work+0x9cf/0x1b70 kernel/workqueue.c:3263
process_scheduled_works kernel/workqueue.c:3346 [inline]
worker_thread+0x6c8/0xf10 kernel/workqueue.c:3427
kthread+0x3c5/0x780 kernel/kthread.c:463
ret_from_fork+0x675/0x7d0 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
page last free pid 5811 tgid 5811 stack trace:
reset_page_owner include/linux/page_owner.h:25 [inline]
free_pages_prepare mm/page_alloc.c:1394 [inline]
__free_frozen_pages+0x7df/0x1160 mm/page_alloc.c:2906
__folio_put+0x329/0x450 mm/swap.c:112
folio_put include/linux/mm.h:1425 [inline]
put_page include/linux/mm.h:1494 [inline]
put_netmem net/core/skbuff.c:7376 [inline]
skb_page_unref include/linux/skbuff_ref.h:43 [inline]
__skb_frag_unref include/linux/skbuff_ref.h:56 [inline]
skb_release_data+0x81a/0x9e0 net/core/skbuff.c:1081
skb_release_all net/core/skbuff.c:1152 [inline]
__kfree_skb+0x4f/0x70 net/core/skbuff.c:1166
tcp_wmem_free_skb include/net/tcp.h:332 [inline]
tcp_rtx_queue_unlink_and_free include/net/tcp.h:2205 [inline]
tcp_clean_rtx_queue net/ipv4/tcp_input.c:3471 [inline]
tcp_ack+0x1d37/0x5fc0 net/ipv4/tcp_input.c:4096
tcp_rcv_established+0x10ea/0x3700 net/ipv4/tcp_input.c:6341
tcp_v4_do_rcv+0xc65/0x10a0 net/ipv4/tcp_ipv4.c:1931
sk_backlog_rcv include/net/sock.h:1158 [inline]
__release_sock+0x361/0x450 net/core/sock.c:3180
release_sock+0x5a/0x220 net/core/sock.c:3735
tcp_recvmsg+0x13a/0x680 net/ipv4/tcp.c:2929
inet_recvmsg+0x129/0x6a0 net/ipv4/af_inet.c:885
sock_recvmsg_nosec net/socket.c:1078 [inline]
sock_recvmsg+0x1b2/0x250 net/socket.c:1100
sock_read_iter+0x2b9/0x3b0 net/socket.c:1170
new_sync_read fs/read_write.c:491 [inline]
vfs_read+0xa98/0xcf0 fs/read_write.c:572
ksys_read+0x1f8/0x250 fs/read_write.c:715
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xcd/0xfa0 arch/x86/entry/syscall_64.c:94
Memory state around the buggy address:
ffff88803b578600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88803b578680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88803b578700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88803b578780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88803b578800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
==================================================================
BUG: KASAN: slab-use-after-free in instrument_atomic_write include/linux/instrumented.h:82 [inline]
BUG: KASAN: slab-use-after-free in set_bit include/asm-generic/bitops/instrumented-atomic.h:28 [inline]
BUG: KASAN: slab-use-after-free in v4l2_fh_init+0xd4/0x2c0 drivers/media/v4l2-core/v4l2-fh.c:27
Write of size 8 at addr ffff88803b5787a8 by task v4l_id/20102
CPU: 1 UID: 0 PID: 20102 Comm: v4l_id Tainted: G B syzkaller #0 PREEMPT(full)
Tainted: [B]=BAD_PAGE
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
Call Trace:
__dump_stack lib/dump_stack.c:94 [inline]
dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120
print_address_description mm/kasan/report.c:378 [inline]
print_report+0xcd/0x630 mm/kasan/report.c:482
kasan_report+0xe0/0x110 mm/kasan/report.c:595
check_region_inline mm/kasan/generic.c:194 [inline]
kasan_check_range+0x100/0x1b0 mm/kasan/generic.c:200
instrument_atomic_write include/linux/instrumented.h:82 [inline]
set_bit include/asm-generic/bitops/instrumented-atomic.h:28 [inline]
v4l2_fh_init+0xd4/0x2c0 drivers/media/v4l2-core/v4l2-fh.c:27
v4l2_fh_open+0x64/0xa0 drivers/media/v4l2-core/v4l2-fh.c:64
em28xx_v4l2_open+0x24e/0x7e0 drivers/media/usb/em28xx/em28xx-video.c:2153
v4l2_open+0x1d2/0x5e0 drivers/media/v4l2-core/v4l2-dev.c:433
chrdev_open+0x234/0x6a0 fs/char_dev.c:414
do_dentry_open+0x982/0x1530 fs/open.c:965
vfs_open+0x82/0x3f0 fs/open.c:1097
do_open fs/namei.c:3975 [inline]
path_openat+0x1de4/0x2cb0 fs/namei.c:4134
do_filp_open+0x20b/0x470 fs/namei.c:4161
do_sys_openat2+0x11b/0x1d0 fs/open.c:1437
do_sys_open fs/open.c:1452 [inline]
__do_sys_openat fs/open.c:1468 [inline]
__se_sys_openat fs/open.c:1463 [inline]
__x64_sys_openat+0x174/0x210 fs/open.c:1463
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xcd/0xfa0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f7e57aa7407
Code: 48 89 fa 4c 89 df e8 38 aa 00 00 8b 93 08 03 00 00 59 5e 48 83 f8 fc 74 1a 5b c3 0f 1f 84 00 00 00 00 00 48 8b 44 24 10 0f 05 <5b> c3 0f 1f 80 00 00 00 00 83 e2 39 83 fa 08 75 de e8 23 ff ff ff
RSP: 002b:00007ffd724c9940 EFLAGS: 00000202 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007f7e58225880 RCX: 00007f7e57aa7407
RDX: 0000000000000000 RSI: 00007ffd724c9f1b RDI: ffffffffffffff9c
RBP: 0000000000000002 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000202 R12: 0000000000000000
R13: 00007ffd724c9b90 R14: 00007f7e5838c000 R15: 00005585bbcf74d8
Allocated by task 5905:
kasan_save_stack+0x33/0x60 mm/kasan/common.c:56
kasan_save_track+0x14/0x30 mm/kasan/common.c:77
poison_kmalloc_redzone mm/kasan/common.c:400 [inline]
__kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:417
kmalloc_noprof include/linux/slab.h:957 [inline]
kzalloc_noprof include/linux/slab.h:1094 [inline]
em28xx_v4l2_init+0x114/0x4080 drivers/media/usb/em28xx/em28xx-video.c:2532
em28xx_init_extension+0x13a/0x200 drivers/media/usb/em28xx/em28xx-core.c:1117
request_module_async+0x61/0x70 drivers/media/usb/em28xx/em28xx-cards.c:3457
process_one_work+0x9cf/0x1b70 kernel/workqueue.c:3263
process_scheduled_works kernel/workqueue.c:3346 [inline]
worker_thread+0x6c8/0xf10 kernel/workqueue.c:3427
kthread+0x3c5/0x780 kernel/kthread.c:463
ret_from_fork+0x675/0x7d0 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
Freed by task 5905:
kasan_save_stack+0x33/0x60 mm/kasan/common.c:56
kasan_save_track+0x14/0x30 mm/kasan/common.c:77
__kasan_save_free_info+0x3b/0x60 mm/kasan/generic.c:587
kasan_save_free_info mm/kasan/kasan.h:406 [inline]
poison_slab_object mm/kasan/common.c:252 [inline]
__kasan_slab_free+0x5f/0x80 mm/kasan/common.c:284
kasan_slab_free include/linux/kasan.h:234 [inline]
slab_free_hook mm/slub.c:2530 [inline]
slab_free mm/slub.c:6619 [inline]
kfree+0x2b8/0x6d0 mm/slub.c:6826
em28xx_free_v4l2 drivers/media/usb/em28xx/em28xx-video.c:2118 [inline]
kref_put include/linux/kref.h:65 [inline]
em28xx_v4l2_init+0x22b5/0x4080 drivers/media/usb/em28xx/em28xx-video.c:2901
em28xx_init_extension+0x13a/0x200 drivers/media/usb/em28xx/em28xx-core.c:1117
request_module_async+0x61/0x70 drivers/media/usb/em28xx/em28xx-cards.c:3457
process_one_work+0x9cf/0x1b70 kernel/workqueue.c:3263
process_scheduled_works kernel/workqueue.c:3346 [inline]
worker_thread+0x6c8/0xf10 kernel/workqueue.c:3427
kthread+0x3c5/0x780 kernel/kthread.c:463
ret_from_fork+0x675/0x7d0 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 ffff88803b578000
which belongs to the cache kmalloc-8k of size 8192
The buggy address is located 1960 bytes inside of
freed 8192-byte region [ffff88803b578000, ffff88803b57a000)
The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x3b578
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 ffff88813ffa7280 dead000000000122 0000000000000000
raw: 0000000000000000 0000000080020002 00000000f5000000 0000000000000000
head: 00fff00000000040 ffff88813ffa7280 dead000000000122 0000000000000000
head: 0000000000000000 0000000080020002 00000000f5000000 0000000000000000
head: 00fff00000000003 ffffea0000ed5e01 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 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 5905, tgid 5905 (kworker/0:4), ts 1194903977210, free_ts 1194903743889
set_page_owner include/linux/page_owner.h:32 [inline]
post_alloc_hook+0x1c0/0x230 mm/page_alloc.c:1850
prep_new_page mm/page_alloc.c:1858 [inline]
get_page_from_freelist+0x10a3/0x3a30 mm/page_alloc.c:3884
__alloc_frozen_pages_noprof+0x25f/0x2470 mm/page_alloc.c:5183
alloc_pages_mpol+0x1fb/0x550 mm/mempolicy.c:2416
alloc_slab_page mm/slub.c:3046 [inline]
allocate_slab mm/slub.c:3219 [inline]
new_slab+0x24a/0x360 mm/slub.c:3273
___slab_alloc+0xdc4/0x1ae0 mm/slub.c:4643
__slab_alloc.constprop.0+0x63/0x110 mm/slub.c:4762
__slab_alloc_node mm/slub.c:4838 [inline]
slab_alloc_node mm/slub.c:5260 [inline]
__kmalloc_cache_noprof+0x477/0x780 mm/slub.c:5750
kmalloc_noprof include/linux/slab.h:957 [inline]
kzalloc_noprof include/linux/slab.h:1094 [inline]
em28xx_v4l2_init+0x114/0x4080 drivers/media/usb/em28xx/em28xx-video.c:2532
em28xx_init_extension+0x13a/0x200 drivers/media/usb/em28xx/em28xx-core.c:1117
request_module_async+0x61/0x70 drivers/media/usb/em28xx/em28xx-cards.c:3457
process_one_work+0x9cf/0x1b70 kernel/workqueue.c:3263
process_scheduled_works kernel/workqueue.c:3346 [inline]
worker_thread+0x6c8/0xf10 kernel/workqueue.c:3427
kthread+0x3c5/0x780 kernel/kthread.c:463
ret_from_fork+0x675/0x7d0 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
page last free pid 5811 tgid 5811 stack trace:
reset_page_owner include/linux/page_owner.h:25 [inline]
free_pages_prepare mm/page_alloc.c:1394 [inline]
__free_frozen_pages+0x7df/0x1160 mm/page_alloc.c:2906
__folio_put+0x329/0x450 mm/swap.c:112
folio_put include/linux/mm.h:1425 [inline]
put_page include/linux/mm.h:1494 [inline]
put_netmem net/core/skbuff.c:7376 [inline]
skb_page_unref include/linux/skbuff_ref.h:43 [inline]
__skb_frag_unref include/linux/skbuff_ref.h:56 [inline]
skb_release_data+0x81a/0x9e0 net/core/skbuff.c:1081
skb_release_all net/core/skbuff.c:1152 [inline]
__kfree_skb+0x4f/0x70 net/core/skbuff.c:1166
tcp_wmem_free_skb include/net/tcp.h:332 [inline]
tcp_rtx_queue_unlink_and_free include/net/tcp.h:2205 [inline]
tcp_clean_rtx_queue net/ipv4/tcp_input.c:3471 [inline]
tcp_ack+0x1d37/0x5fc0 net/ipv4/tcp_input.c:4096
tcp_rcv_established+0x10ea/0x3700 net/ipv4/tcp_input.c:6341
tcp_v4_do_rcv+0xc65/0x10a0 net/ipv4/tcp_ipv4.c:1931
sk_backlog_rcv include/net/sock.h:1158 [inline]
__release_sock+0x361/0x450 net/core/sock.c:3180
release_sock+0x5a/0x220 net/core/sock.c:3735
tcp_recvmsg+0x13a/0x680 net/ipv4/tcp.c:2929
inet_recvmsg+0x129/0x6a0 net/ipv4/af_inet.c:885
sock_recvmsg_nosec net/socket.c:1078 [inline]
sock_recvmsg+0x1b2/0x250 net/socket.c:1100
sock_read_iter+0x2b9/0x3b0 net/socket.c:1170
new_sync_read fs/read_write.c:491 [inline]
vfs_read+0xa98/0xcf0 fs/read_write.c:572
ksys_read+0x1f8/0x250 fs/read_write.c:715
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xcd/0xfa0 arch/x86/entry/syscall_64.c:94
Memory state around the buggy address:
ffff88803b578680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88803b578700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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