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BUG: KASAN: use-after-free in strlen+0x79/0x90 lib/string.c:544
Read of size 1 at addr ffff8881ca064a08 by task syz-executor.0/30998

CPU: 1 PID: 30998 Comm: syz-executor.0 Not tainted 5.6.0-rc1-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+0xef/0x16e lib/dump_stack.c:118
 print_address_description.constprop.0.cold+0xd3/0x314 mm/kasan/report.c:374
 __kasan_report.cold+0x37/0x77 mm/kasan/report.c:506
 kasan_report+0xe/0x20 mm/kasan/common.c:641
 strlen+0x79/0x90 lib/string.c:544
 strlen include/linux/string.h:303 [inline]
 str_to_user+0x27/0x90 drivers/input/evdev.c:780
 evdev_do_ioctl drivers/input/evdev.c:1183 [inline]
 evdev_ioctl_handler+0x130a/0x19f0 drivers/input/evdev.c:1281
 vfs_ioctl fs/ioctl.c:47 [inline]
 ksys_ioctl+0x11a/0x180 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+0xb6/0x5a0 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45c429
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:00007f1082223c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f10822246d4 RCX: 000000000045c429
RDX: 00000000200001c0 RSI: 0000000080404507 RDI: 0000000000000008
RBP: 000000000076bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 00000000000002cb R14: 00000000004c4d98 R15: 000000000076bf2c

The buggy address belongs to the page:
page:ffffea0007281900 refcount:0 mapcount:0 mapping:0000000000000000 index:0x0
flags: 0x200000000000000()
raw: 0200000000000000 0000000000000000 ffffea0007281908 0000000000000000
raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8881ca064900: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff8881ca064980: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff8881ca064a00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                      ^
 ffff8881ca064a80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff8881ca064b00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
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