<div dir="ltr"><div>Hello team, <br></div><div>i want to report a bug on linux kernel on vgacon.c:669</div><div><br></div><div><pre style="color:rgb(0,0,0);font-style:normal;font-variant-ligatures:normal;font-variant-caps:normal;font-weight:400;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;word-spacing:0px;text-decoration-style:initial;text-decoration-color:initial;white-space:pre-wrap">==================================================================
BUG: KASAN: use-after-free in vgacon_invert_region+0xda/0xe0 drivers/video/console/vgacon.c:669
Read of size 2 at addr ffff888000107ec0 by task syz-executor.6/31018

CPU: 1 PID: 31018 Comm: syz-executor.6 Not tainted 5.6.0-rc3 #1
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Ubuntu-1.8.2-1ubuntu1 04/01/2014
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0xc6/0x11e lib/dump_stack.c:118
 print_address_description.constprop.5+0x16/0x310 mm/kasan/report.c:374
 __kasan_report+0x158/0x1c0 mm/kasan/report.c:506
 kasan_report+0xe/0x20 mm/kasan/common.c:641
 vgacon_invert_region+0xda/0xe0 drivers/video/console/vgacon.c:669
 invert_screen+0x16c/0x580 drivers/tty/vt/vt.c:763
 highlight drivers/tty/vt/selection.c:57 [inline]
 set_selection_kernel+0x9d0/0x11b0 drivers/tty/vt/selection.c:304
 set_selection_user+0x87/0xd0 drivers/tty/vt/selection.c:181
 tioclinux+0x359/0x480 drivers/tty/vt/vt.c:3050
 vt_ioctl+0x13c2/0x24f0 drivers/tty/vt/vt_ioctl.c:364
 tty_ioctl+0x27b/0x13f0 drivers/tty/tty_io.c:2660
 vfs_ioctl fs/ioctl.c:47 [inline]
 ksys_ioctl+0xeb/0x120 fs/ioctl.c:763
 __do_sys_ioctl fs/ioctl.c:772 [inline]
 __se_sys_ioctl fs/ioctl.c:770 [inline]
 __x64_sys_ioctl+0x6f/0xb0 fs/ioctl.c:770
 do_syscall_64+0x9b/0x520 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45c679
Code: ad b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 7b b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007ff254c8fc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007ff254c906d4 RCX: 000000000045c679
RDX: 0000000020000200 RSI: 000000000000541c RDI: 0000000000000003
RBP: 000000000076bf00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 0000000000000574 R14: 00000000004c7eac R15: 000000000076bf0c

The buggy address belongs to the page:
page:ffffea00000041c0 refcount:0 mapcount:0 mapping:0000000000000000 index:0x0
flags: 0x0()
raw: 0000000000000000 ffff88802587fab0 ffff88802587fab0 0000000000000000
raw: 0000000000000000 ffff88806778ee00 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff888000107d80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888000107e00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff888000107e80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                                           ^
 ffff888000107f00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888000107f80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================</pre></div><br></div>