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BUG: KASAN: use-after-free in memcpy include/linux/string.h:348 [inline]
BUG: KASAN: use-after-free in soft_cursor+0x439/0xa30 drivers/video/fbdev/core/softcursor.c:70
Read of size 31 at addr ffff88807b929670 by task kworker/0:0/25628

CPU: 0 PID: 25628 Comm: kworker/0:0 Not tainted 4.19.91-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+0x197/0x210 lib/dump_stack.c:118
 print_address_description.cold+0x7c/0x20d mm/kasan/report.c:256
 kasan_report_error mm/kasan/report.c:354 [inline]
 kasan_report mm/kasan/report.c:412 [inline]
 kasan_report.cold+0x8c/0x2ba mm/kasan/report.c:396
 check_memory_region_inline mm/kasan/kasan.c:260 [inline]
 check_memory_region+0x123/0x190 mm/kasan/kasan.c:267
 memcpy+0x24/0x50 mm/kasan/kasan.c:302
 memcpy include/linux/string.h:348 [inline]
 soft_cursor+0x439/0xa30 drivers/video/fbdev/core/softcursor.c:70
 bit_cursor+0x12fc/0x1a60 drivers/video/fbdev/core/bitblit.c:386
 fb_flashcursor+0x3a6/0x450 drivers/video/fbdev/core/fbcon.c:399
 process_one_work+0x989/0x1750 kernel/workqueue.c:2153
 worker_thread+0x98/0xe40 kernel/workqueue.c:2296
 kthread+0x354/0x420 kernel/kthread.c:246
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415

Allocated by task 7035:
 save_stack+0x45/0xd0 mm/kasan/kasan.c:448
 set_track mm/kasan/kasan.c:460 [inline]
 kasan_kmalloc mm/kasan/kasan.c:553 [inline]
 kasan_kmalloc+0xce/0xf0 mm/kasan/kasan.c:531
 __do_kmalloc_node mm/slab.c:3689 [inline]
 __kmalloc_node_track_caller+0x51/0x80 mm/slab.c:3703
 __kmalloc_reserve.isra.0+0x40/0xf0 net/core/skbuff.c:137
 __alloc_skb+0x10b/0x5f0 net/core/skbuff.c:205
 alloc_skb include/linux/skbuff.h:995 [inline]
 alloc_skb_with_frags+0x93/0x590 net/core/skbuff.c:5303
 sock_alloc_send_pskb+0x72d/0x8a0 net/core/sock.c:2085
 sock_alloc_send_skb+0x32/0x40 net/core/sock.c:2102
 __ip6_append_data.isra.0+0x1c8e/0x2fb0 net/ipv6/ip6_output.c:1421
 ip6_make_skb+0x32f/0x561 net/ipv6/ip6_output.c:1777
 udpv6_sendmsg+0x225b/0x2a00 net/ipv6/udp.c:1402
 inet_sendmsg+0x141/0x5d0 net/ipv4/af_inet.c:798
 sock_sendmsg_nosec net/socket.c:622 [inline]
 sock_sendmsg+0xd7/0x130 net/socket.c:632
 ___sys_sendmsg+0x3e2/0x920 net/socket.c:2115
 __sys_sendmmsg+0x1bf/0x4e0 net/socket.c:2210
 __do_sys_sendmmsg net/socket.c:2239 [inline]
 __se_sys_sendmmsg net/socket.c:2236 [inline]
 __x64_sys_sendmmsg+0x9d/0x100 net/socket.c:2236
 do_syscall_64+0xfd/0x620 arch/x86/entry/common.c:293
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 7030:
 save_stack+0x45/0xd0 mm/kasan/kasan.c:448
 set_track mm/kasan/kasan.c:460 [inline]
 __kasan_slab_free+0x102/0x150 mm/kasan/kasan.c:521
 kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528
 __cache_free mm/slab.c:3503 [inline]
 kfree+0xcf/0x220 mm/slab.c:3822
 skb_free_head+0x99/0xc0 net/core/skbuff.c:554
 skb_release_data+0x619/0x8d0 net/core/skbuff.c:574
 __consume_stateless_skb+0x6e/0x2e0 net/core/skbuff.c:719
 skb_consume_udp net/ipv4/udp.c:1500 [inline]
 skb_consume_udp+0x134/0x2a0 net/ipv4/udp.c:1483
 udpv6_recvmsg+0xb2d/0x1ab0 net/ipv6/udp.c:445
 inet_recvmsg+0x136/0x5f0 net/ipv4/af_inet.c:830
 sock_recvmsg_nosec+0x89/0xb0 net/socket.c:795
 ___sys_recvmsg+0x271/0x580 net/socket.c:2277
 __sys_recvmmsg+0x27e/0x790 net/socket.c:2389
 do_sys_recvmmsg net/socket.c:2465 [inline]
 do_sys_recvmmsg+0x181/0x1a0 net/socket.c:2454
 __do_sys_recvmmsg net/socket.c:2483 [inline]
 __se_sys_recvmmsg net/socket.c:2479 [inline]
 __x64_sys_recvmmsg+0xbe/0x150 net/socket.c:2479
 do_syscall_64+0xfd/0x620 arch/x86/entry/common.c:293
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff88807b929500
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 368 bytes inside of
 512-byte region [ffff88807b929500, ffff88807b929700)
The buggy address belongs to the page:
page:ffffea0001ee4a40 count:1 mapcount:0 mapping:ffff88812c31c940 index:0xffff88807b929a00
flags: 0xfffe0000000100(slab)
raw: 00fffe0000000100 ffffea0001257588 ffffea0002a47a08 ffff88812c31c940
raw: ffff88807b929a00 ffff88807b929000 0000000100000001 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff88807b929500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88807b929580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88807b929600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                             ^
 ffff88807b929680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88807b929700: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
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