================================================================== BUG: KASAN: use-after-free in fbcon_cursor+0x59d/0x690 drivers/video/fbdev/core/fbcon.c:1325 Read of size 2 at addr ffff8880a5ba93ae by task syz-executor.0/28552 CPU: 0 PID: 28552 Comm: syz-executor.0 Not tainted 4.14.173-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_cursor+0x59d/0x690 drivers/video/fbdev/core/fbcon.c:1325 fbcon_scrolldelta+0x57f/0x10c0 drivers/video/fbdev/core/fbcon.c:2832 fbcon_set_origin+0x32/0x40 drivers/video/fbdev/core/fbcon.c:2883 set_origin+0x2cc/0x3b0 drivers/tty/vt/vt.c:613 vc_do_resize+0x603/0xe10 drivers/tty/vt/vt.c:934 vt_ioctl+0x1a08/0x1f00 drivers/tty/vt/vt_ioctl.c:891 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: 0033:0x45c6c9 RSP: 002b:00007fc8c22b4c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00007fc8c22b56d4 RCX: 000000000045c6c9 RDX: 0000000020000040 RSI: 000000000000560a RDI: 0000000000000003 RBP: 000000000076bf20 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff R13: 000000000000066b R14: 00000000004c926c R15: 000000000076bf2c Allocated by task 1: 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] kzalloc include/linux/slab.h:661 [inline] vc_do_resize+0x1c1/0xe10 drivers/tty/vt/vt.c:872 fbcon_init+0xf83/0x19a0 drivers/video/fbdev/core/fbcon.c:1157 visual_init+0x332/0x5e0 drivers/tty/vt/vt.c:745 do_bind_con_driver+0x4de/0x7f0 drivers/tty/vt/vt.c:3182 do_take_over_console+0x3ef/0x4f0 drivers/tty/vt/vt.c:3743 do_fbcon_takeover+0xe4/0x1c0 drivers/video/fbdev/core/fbcon.c:545 fbcon_fb_registered drivers/video/fbdev/core/fbcon.c:3183 [inline] fbcon_event_notify+0x12e6/0x1746 drivers/video/fbdev/core/fbcon.c:3313 notifier_call_chain+0x107/0x1a0 kernel/notifier.c:93 __blocking_notifier_call_chain kernel/notifier.c:317 [inline] __blocking_notifier_call_chain kernel/notifier.c:304 [inline] blocking_notifier_call_chain kernel/notifier.c:328 [inline] blocking_notifier_call_chain+0x79/0x90 kernel/notifier.c:325 do_register_framebuffer drivers/video/fbdev/core/fbmem.c:1719 [inline] register_framebuffer+0x512/0x8f0 drivers/video/fbdev/core/fbmem.c:1839 vga16fb_probe+0x6a7/0x79c drivers/video/fbdev/vga16fb.c:1374 platform_drv_probe+0x85/0x170 drivers/base/platform.c:583 really_probe drivers/base/dd.c:408 [inline] driver_probe_device+0x4ab/0x670 drivers/base/dd.c:551 __device_attach_driver+0x1fd/0x290 drivers/base/dd.c:647 bus_for_each_drv+0x145/0x1b0 drivers/base/bus.c:466 __device_attach+0x1dd/0x2c0 drivers/base/dd.c:704 bus_probe_device+0x1db/0x290 drivers/base/bus.c:526 device_add+0xa0a/0x1400 drivers/base/core.c:1917 platform_device_add+0x2ec/0x660 drivers/base/platform.c:421 vga16fb_init+0x11e/0x173 drivers/video/fbdev/vga16fb.c:1432 do_one_initcall+0x88/0x202 init/main.c:824 do_initcall_level init/main.c:890 [inline] do_initcalls init/main.c:898 [inline] do_basic_setup init/main.c:916 [inline] kernel_init_freeable+0x465/0x526 init/main.c:1073 kernel_init+0xd/0x15b init/main.c:998 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404 Freed by task 28552: 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 vc_do_resize+0x5a7/0xe10 drivers/tty/vt/vt.c:931 vt_ioctl+0x1a08/0x1f00 drivers/tty/vt/vt_ioctl.c:891 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 The buggy address belongs to the object at ffff8880a5ba8140 which belongs to the cache kmalloc-8192 of size 8192 The buggy address is located 4718 bytes inside of 8192-byte region [ffff8880a5ba8140, ffff8880a5baa140) The buggy address belongs to the page: page:ffffea000296ea00 count:1 mapcount:0 mapping:ffff8880a5ba8140 index:0x0 compound_mapcount: 0 flags: 0xfffe0000008100(slab|head) raw: 00fffe0000008100 ffff8880a5ba8140 0000000000000000 0000000100000001 raw: ffffea0002990320 ffffea00028d1320 ffff88812fe55080 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff8880a5ba9280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff8880a5ba9300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >ffff8880a5ba9380: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff8880a5ba9400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff8880a5ba9480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ==================================================================