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BUG: KASAN: slab-out-of-bounds in fbcon_get_font+0x5fc/0x660 drivers/video/fbdev/core/fbcon.c:2440
Read of size 1 at addr ffff8880558d6450 by task syz-executor.0/26826

CPU: 0 PID: 26826 Comm: syz-executor.0 Not tainted 4.14.189-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0x1b2/0x283 lib/dump_stack.c:58
 print_address_description.cold+0x54/0x1d3 mm/kasan/report.c:252
 kasan_report_error.cold+0x8a/0x194 mm/kasan/report.c:351
 kasan_report mm/kasan/report.c:409 [inline]
 __asan_report_load1_noabort+0x68/0x70 mm/kasan/report.c:427
 fbcon_get_font+0x5fc/0x660 drivers/video/fbdev/core/fbcon.c:2440
 con_font_get drivers/tty/vt/vt.c:4098 [inline]
 con_font_op+0x1c6/0xf60 drivers/tty/vt/vt.c:4249
 do_fontx_ioctl drivers/tty/vt/vt_ioctl.c:273 [inline]
 vt_ioctl+0x14e3/0x1ea0 drivers/tty/vt/vt_ioctl.c:945
 tty_ioctl+0x50f/0x13c0 drivers/tty/tty_io.c:2661
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:500 [inline]
 do_vfs_ioctl+0x75a/0xff0 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+0x46/0xbb
RIP: 0033:0x45c369
RSP: 002b:00007fb0a8047c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 000000000000e500 RCX: 000000000045c369
RDX: 00000000200000c0 RSI: 0000000000004b6b RDI: 0000000000000008
RBP: 000000000078bf40 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000078bf0c
R13: 00007ffcb55e48af R14: 00007fb0a80489c0 R15: 000000000078bf0c

Allocated by task 21535:
 save_stack mm/kasan/kasan.c:447 [inline]
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_kmalloc+0xeb/0x160 mm/kasan/kasan.c:551
 __do_kmalloc mm/slab.c:3720 [inline]
 __kmalloc+0x15a/0x400 mm/slab.c:3729
 kmalloc include/linux/slab.h:493 [inline]
 fbcon_set_font+0x2fb/0x7c0 drivers/video/fbdev/core/fbcon.c:2621
 con_font_set drivers/tty/vt/vt.c:4182 [inline]
 con_font_op+0xb69/0xf60 drivers/tty/vt/vt.c:4247
 vt_ioctl+0x127b/0x1ea0 drivers/tty/vt/vt_ioctl.c:980
 tty_ioctl+0x50f/0x13c0 drivers/tty/tty_io.c:2661
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:500 [inline]
 do_vfs_ioctl+0x75a/0xff0 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+0x46/0xbb

Freed by task 0:
(stack is not available)

The buggy address belongs to the object at ffff8880558d3a40
 which belongs to the cache kmalloc-16384 of size 16384
The buggy address is located 10768 bytes inside of
 16384-byte region [ffff8880558d3a40, ffff8880558d7a40)
The buggy address belongs to the page:
page:ffffea0001563400 count:1 mapcount:0 mapping:ffff8880558d3a40 index:0x0 compound_mapcount: 0
flags: 0xfffe0000008100(slab|head)
raw: 00fffe0000008100 ffff8880558d3a40 0000000000000000 0000000100000001
raw: ffffea00025f9e20 ffffea0001186820 ffff88812fe45200 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8880558d6300: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff8880558d6380: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff8880558d6400: 00 00 00 00 00 00 00 00 00 00 fc fc fc fc fc fc
                                                 ^
 ffff8880558d6480: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8880558d6500: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
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