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BUG: KASAN: use-after-free in vcs_read_buf drivers/tty/vt/vc_screen.c:357 [inline]
BUG: KASAN: use-after-free in vcs_read+0xaa7/0xb40 drivers/tty/vt/vc_screen.c:449
Write of size 2 at addr ffff8882140e1000 by task syz-executor.0/18673

CPU: 1 PID: 18673 Comm: syz-executor.0 Not tainted 5.9.0-rc2-next-20200825-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x18f/0x20d lib/dump_stack.c:118
 print_address_description.constprop.0.cold+0xae/0x497 mm/kasan/report.c:383
 __kasan_report mm/kasan/report.c:513 [inline]
 kasan_report.cold+0x1f/0x37 mm/kasan/report.c:530
 vcs_read_buf drivers/tty/vt/vc_screen.c:357 [inline]
 vcs_read+0xaa7/0xb40 drivers/tty/vt/vc_screen.c:449
 vfs_read+0x1df/0x5a0 fs/read_write.c:479
 ksys_read+0x12d/0x250 fs/read_write.c:607
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x45d579
Code: 5d b4 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 2b b4 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fb8e306dc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
RAX: ffffffffffffffda RBX: 0000000000025e80 RCX: 000000000045d579
RDX: 0000000000002020 RSI: 0000000020002bc0 RDI: 0000000000000003
RBP: 000000000118cf80 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000118cf4c
R13: 00007ffc6f24abbf R14: 00007fb8e306e9c0 R15: 000000000118cf4c

The buggy address belongs to the page:
page:000000000ccc2760 refcount:0 mapcount:-128 mapping:0000000000000000 index:0x0 pfn:0x2140e1
flags: 0x57ffe0000000000()
raw: 057ffe0000000000 ffffea00086c4948 ffffea0008508248 0000000000000000
raw: 0000000000000000 0000000000000000 00000000ffffff7f 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8882140e0f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff8882140e0f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff8882140e1000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                   ^
 ffff8882140e1080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff8882140e1100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
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