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BUG: KASAN: slab-out-of-bounds in fbcon_get_font+0x508/0x530 drivers/video/fbdev/core/fbcon.c:2437
Read of size 1 at addr ffff88804ff94490 by task syz-executor.4/10464

CPU: 1 PID: 10464 Comm: syz-executor.4 Not tainted 4.14.174-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+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
 fbcon_get_font+0x508/0x530 drivers/video/fbdev/core/fbcon.c:2437
 con_font_get drivers/tty/vt/vt.c:4076 [inline]
 con_font_op+0x1c6/0xf70 drivers/tty/vt/vt.c:4227
 do_fontx_ioctl drivers/tty/vt/vt_ioctl.c:252 [inline]
 vt_ioctl+0x174b/0x1f00 drivers/tty/vt/vt_ioctl.c:935
 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
RIP: 0033:0x45c849
RSP: 002b:00007fc690d72c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007fc690d736d4 RCX: 000000000045c849
RDX: 0000000020000940 RSI: 0000000000004b6b RDI: 0000000000000003
RBP: 000000000076bf00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 0000000000000328 R14: 00000000004c58d0 R15: 000000000076bf0c

Allocated by task 10453:
 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:2618
 con_font_set drivers/tty/vt/vt.c:4160 [inline]
 con_font_op+0xb73/0xf70 drivers/tty/vt/vt.c:4225
 vt_ioctl+0x1334/0x1f00 drivers/tty/vt/vt_ioctl.c:970
 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 5:
 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
 ops_free net/core/net_namespace.c:132 [inline]
 ops_free_list.part.0+0x1f9/0x330 net/core/net_namespace.c:154
 ops_free_list net/core/net_namespace.c:152 [inline]
 cleanup_net+0x453/0x820 net/core/net_namespace.c:488
 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

The buggy address belongs to the object at ffff88804ff90e80
 which belongs to the cache kmalloc-16384 of size 16384
The buggy address is located 13840 bytes inside of
 16384-byte region [ffff88804ff90e80, ffff88804ff94e80)
The buggy address belongs to the page:
page:ffffea00013fe400 count:1 mapcount:0 mapping:ffff88804ff90e80 index:0x0 compound_mapcount: 0
flags: 0xfffe0000008100(slab|head)
raw: 00fffe0000008100 ffff88804ff90e80 0000000000000000 0000000100000001
raw: ffffea0001441620 ffffea000151aa20 ffff88812fe55200 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff88804ff94380: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff88804ff94400: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff88804ff94480: 00 00 fc fc fc fc fc fc fc fc fc fc fc fc fc fc
                         ^
 ffff88804ff94500: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88804ff94580: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
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