==================================================================
BUG: KASAN: use-after-free in strlen+0x79/0x90 lib/string.c:544
Read of size 1 at addr ffff8881ab062208 by task syz-executor.3/15130

CPU: 0 PID: 15130 Comm: syz-executor.3 Not tainted 5.6.0-rc7-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: 0033:0x45c849
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:00007f493acc1c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f493acc26d4 RCX: 000000000045c849
RDX: 0000000020000280 RSI: 0000000080404507 RDI: 0000000000000007
RBP: 000000000076bf00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 00000000000002ca R14: 00000000004c51be R15: 000000000076bf0c

Allocated by task 14642:
 save_stack+0x1b/0x80 mm/kasan/common.c:72
 set_track mm/kasan/common.c:80 [inline]
 __kasan_kmalloc mm/kasan/common.c:515 [inline]
 __kasan_kmalloc.constprop.0+0xbf/0xd0 mm/kasan/common.c:488
 slab_post_alloc_hook mm/slab.h:584 [inline]
 slab_alloc_node mm/slub.c:2786 [inline]
 slab_alloc mm/slub.c:2794 [inline]
 kmem_cache_alloc+0xd8/0x300 mm/slub.c:2799
 getname_flags fs/namei.c:138 [inline]
 getname_flags+0xd2/0x5b0 fs/namei.c:128
 user_path_at_empty+0x2a/0x50 fs/namei.c:2746
 user_path_at include/linux/namei.h:58 [inline]
 do_faccessat+0x248/0x7a0 fs/open.c:398
 do_syscall_64+0xb6/0x5a0 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 14642:
 save_stack+0x1b/0x80 mm/kasan/common.c:72
 set_track mm/kasan/common.c:80 [inline]
 kasan_set_free_info mm/kasan/common.c:337 [inline]
 __kasan_slab_free+0x117/0x160 mm/kasan/common.c:476
 slab_free_hook mm/slub.c:1444 [inline]
 slab_free_freelist_hook mm/slub.c:1477 [inline]
 slab_free mm/slub.c:3034 [inline]
 kmem_cache_free+0x9b/0x360 mm/slub.c:3050
 putname+0xe1/0x120 fs/namei.c:259
 filename_lookup+0x282/0x3e0 fs/namei.c:2475
 user_path_at include/linux/namei.h:58 [inline]
 do_faccessat+0x248/0x7a0 fs/open.c:398
 do_syscall_64+0xb6/0x5a0 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff8881ab062200
 which belongs to the cache names_cache of size 4096
The buggy address is located 8 bytes inside of
 4096-byte region [ffff8881ab062200, ffff8881ab063200)
The buggy address belongs to the page:
page:ffffea0006ac1800 refcount:1 mapcount:0 mapping:ffff8881da11c000 index:0x0 compound_mapcount: 0
flags: 0x200000000010200(slab|head)
raw: 0200000000010200 0000000000000000 0000000200000001 ffff8881da11c000
raw: 0000000000000000 0000000000070007 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8881ab062100: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8881ab062180: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8881ab062200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                      ^
 ffff8881ab062280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8881ab062300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================