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BUG: KASAN: slab-out-of-bounds in soft_cursor+0x95d/0xa40 drivers/video/fbdev/core/softcursor.c:61
Read of size 1 at addr ffff8880a6d1e470 by task kworker/1:3/17312

CPU: 1 PID: 17312 Comm: kworker/1:3 Not tainted 4.14.179-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:17 [inline]
 dump_stack+0x13e/0x194 lib/dump_stack.c:58
 print_address_description.cold+0x7c/0x1e2 mm/kasan/report.c:252
 kasan_report_error mm/kasan/report.c:351 [inline]
 kasan_report mm/kasan/report.c:409 [inline]
 kasan_report.cold+0xa9/0x2ae mm/kasan/report.c:393
 soft_cursor+0x95d/0xa40 drivers/video/fbdev/core/softcursor.c:61
 bit_cursor+0x10d9/0x1700 drivers/video/fbdev/core/bitblit.c:386
 fb_flashcursor+0x360/0x400 drivers/video/fbdev/core/fbcon.c:393
 process_one_work+0x813/0x1540 kernel/workqueue.c:2116
 worker_thread+0x5d1/0x1070 kernel/workqueue.c:2250
 kthread+0x30d/0x420 kernel/kthread.c:232
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404

Allocated by task 10601:
 save_stack+0x32/0xa0 mm/kasan/kasan.c:447
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_kmalloc mm/kasan/kasan.c:551 [inline]
 kasan_kmalloc+0xbf/0xe0 mm/kasan/kasan.c:529
 __do_kmalloc mm/slab.c:3720 [inline]
 __kmalloc+0x15b/0x7c0 mm/slab.c:3729
 kmalloc include/linux/slab.h:493 [inline]
 fbcon_set_font+0x2f8/0x7c0 drivers/video/fbdev/core/fbcon.c:2621
 con_font_set drivers/tty/vt/vt.c:4182 [inline]
 con_font_op+0xb73/0xf70 drivers/tty/vt/vt.c:4247
 vt_ioctl+0x736/0x1f20 drivers/tty/vt/vt_ioctl.c:928
 tty_ioctl+0x6c5/0x1220 drivers/tty/tty_io.c:2661
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:500 [inline]
 do_vfs_ioctl+0x75a/0xfe0 fs/ioctl.c:684
 SYSC_ioctl fs/ioctl.c:701 [inline]
 SyS_ioctl+0x7f/0xb0 fs/ioctl.c:692
 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x42/0xb7

Freed by task 9828:
 save_stack+0x32/0xa0 mm/kasan/kasan.c:447
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_slab_free+0x75/0xc0 mm/kasan/kasan.c:524
 __cache_free mm/slab.c:3496 [inline]
 kfree+0xcb/0x260 mm/slab.c:3815
 skb_free_head+0x83/0xa0 net/core/skbuff.c:554
 skb_release_data+0x528/0x7b0 net/core/skbuff.c:574
 skb_release_all+0x46/0x60 net/core/skbuff.c:631
 __kfree_skb net/core/skbuff.c:645 [inline]
 consume_skb+0xa7/0x330 net/core/skbuff.c:705
 netlink_unicast_kernel net/netlink/af_netlink.c:1288 [inline]
 netlink_unicast+0x43f/0x620 net/netlink/af_netlink.c:1313
 netlink_sendmsg+0x733/0xbe0 net/netlink/af_netlink.c:1878
 sock_sendmsg_nosec net/socket.c:646 [inline]
 sock_sendmsg+0xc5/0x100 net/socket.c:656
 ___sys_sendmsg+0x70a/0x840 net/socket.c:2062
 __sys_sendmsg+0xa3/0x120 net/socket.c:2096
 SYSC_sendmsg net/socket.c:2107 [inline]
 SyS_sendmsg+0x27/0x40 net/socket.c:2103
 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x42/0xb7

The buggy address belongs to the object at ffff8880a6d1e340
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 304 bytes inside of
 512-byte region [ffff8880a6d1e340, ffff8880a6d1e540)
The buggy address belongs to the page:
page:ffffea00029b4780 count:1 mapcount:0 mapping:ffff8880a6d1e0c0 index:0x0
flags: 0xfffe0000000100(slab)
raw: 00fffe0000000100 ffff8880a6d1e0c0 0000000000000000 0000000100000006
raw: ffffea0002396ca0 ffffea0002a1f220 ffff88812fe54940 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8880a6d1e300: fc fc fc fc fc fc fc fc 00 00 00 00 00 00 00 00
 ffff8880a6d1e380: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff8880a6d1e400: 00 00 00 00 00 00 00 00 00 00 fc fc fc fc fc fc
                                                             ^
 ffff8880a6d1e480: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8880a6d1e500: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
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