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BUG: KASAN: use-after-free in memcpy include/linux/string.h:406 [inline]
BUG: KASAN: use-after-free in soft_cursor+0x44b/0xa30 drivers/video/fbdev/core/softcursor.c:70
Read of size 9 at addr ffff8880a68cc892 by task kworker/0:0/26765

CPU: 0 PID: 26765 Comm: kworker/0:0 Not tainted 5.9.0-rc4-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: events_power_efficient fb_flashcursor
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x198/0x1fd lib/dump_stack.c:118
 print_address_description.constprop.0.cold+0xae/0x497 mm/kasan/report.c:383
 __kasan_report mm/kasan/report.c:513 [inline]
 kasan_report.cold+0x1f/0x37 mm/kasan/report.c:530
 check_memory_region_inline mm/kasan/generic.c:186 [inline]
 check_memory_region+0x13d/0x180 mm/kasan/generic.c:192
 memcpy+0x20/0x60 mm/kasan/common.c:105
 memcpy include/linux/string.h:406 [inline]
 soft_cursor+0x44b/0xa30 drivers/video/fbdev/core/softcursor.c:70
 bit_cursor+0x1166/0x17d0 drivers/video/fbdev/core/bitblit.c:386
 fb_flashcursor+0x374/0x3e0 drivers/video/fbdev/core/fbcon.c:417
 process_one_work+0x94c/0x1670 kernel/workqueue.c:2269
 worker_thread+0x64c/0x1120 kernel/workqueue.c:2415
 kthread+0x3b5/0x4a0 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294

Allocated by task 32633:
 kasan_save_stack+0x1b/0x40 mm/kasan/common.c:48
 kasan_set_track mm/kasan/common.c:56 [inline]
 __kasan_kmalloc.constprop.0+0xbf/0xd0 mm/kasan/common.c:461
 __kmalloc_reserve net/core/skbuff.c:142 [inline]
 __alloc_skb+0xae/0x550 net/core/skbuff.c:210
 alloc_skb include/linux/skbuff.h:1094 [inline]
 alloc_skb_with_frags+0x92/0x570 net/core/skbuff.c:5771
 sock_alloc_send_pskb+0x72a/0x880 net/core/sock.c:2348
 packet_alloc_skb net/packet/af_packet.c:2837 [inline]
 packet_snd net/packet/af_packet.c:2932 [inline]
 packet_sendmsg+0x19fb/0x5290 net/packet/af_packet.c:3014
 sock_sendmsg_nosec net/socket.c:651 [inline]
 sock_sendmsg+0xcf/0x120 net/socket.c:671
 ____sys_sendmsg+0x331/0x810 net/socket.c:2353
 ___sys_sendmsg+0xf3/0x170 net/socket.c:2407
 __sys_sendmmsg+0x195/0x480 net/socket.c:2497
 __do_sys_sendmmsg net/socket.c:2526 [inline]
 __se_sys_sendmmsg net/socket.c:2523 [inline]
 __x64_sys_sendmmsg+0x99/0x100 net/socket.c:2523
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Freed by task 32633:
 kasan_save_stack+0x1b/0x40 mm/kasan/common.c:48
 kasan_set_track+0x1c/0x30 mm/kasan/common.c:56
 kasan_set_free_info+0x1b/0x30 mm/kasan/generic.c:355
 __kasan_slab_free+0xd8/0x120 mm/kasan/common.c:422
 __cache_free mm/slab.c:3418 [inline]
 kfree+0x10e/0x2b0 mm/slab.c:3756
 skb_free_head net/core/skbuff.c:590 [inline]
 skb_release_data+0x6d9/0x910 net/core/skbuff.c:610
 skb_release_all net/core/skbuff.c:664 [inline]
 __kfree_skb net/core/skbuff.c:678 [inline]
 kfree_skb.part.0+0xc2/0x350 net/core/skbuff.c:696
 kfree_skb+0x7d/0x100 include/linux/refcount.h:270
 vti6_tnl_xmit+0xbb9/0x1cb0 net/ipv6/ip6_vti.c:600
 __netdev_start_xmit include/linux/netdevice.h:4634 [inline]
 netdev_start_xmit include/linux/netdevice.h:4648 [inline]
 dev_direct_xmit+0x4e9/0x6e0 net/core/dev.c:4203
 packet_snd net/packet/af_packet.c:2989 [inline]
 packet_sendmsg+0x2413/0x5290 net/packet/af_packet.c:3014
 sock_sendmsg_nosec net/socket.c:651 [inline]
 sock_sendmsg+0xcf/0x120 net/socket.c:671
 ____sys_sendmsg+0x331/0x810 net/socket.c:2353
 ___sys_sendmsg+0xf3/0x170 net/socket.c:2407
 __sys_sendmmsg+0x195/0x480 net/socket.c:2497
 __do_sys_sendmmsg net/socket.c:2526 [inline]
 __se_sys_sendmmsg net/socket.c:2523 [inline]
 __x64_sys_sendmmsg+0x99/0x100 net/socket.c:2523
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

The buggy address belongs to the object at ffff8880a68cc800
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 146 bytes inside of
 512-byte region [ffff8880a68cc800, ffff8880a68cca00)
The buggy address belongs to the page:
page:000000003b851b93 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0xa68cc
flags: 0xfffe0000000200(slab)
raw: 00fffe0000000200 ffffea00024ec9c8 ffffea000264f1c8 ffff8880aa040600
raw: 0000000000000000 ffff8880a68cc000 0000000100000004 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8880a68cc780: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8880a68cc800: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8880a68cc880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                         ^
 ffff8880a68cc900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8880a68cc980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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