Re: KASAN: slab-out-of-bounds Read in hidraw_ioctl

[syzbot]

syzbot has found a reproducer for the following crash on:

HEAD commit:    e96407b4 usb-fuzzer: main usb gadget fuzzer driver
git tree:       https://github.com/google/kasan.git usb-fuzzer
console output: https://syzkaller.appspot.com/x/log.txt?x=150426ba600000
kernel config:  https://syzkaller.appspot.com/x/.config?x=cfa2c18fb6a8068e
dashboard link: https://syzkaller.appspot.com/bug?extid=5a6c4ec678a0c6ee84ba
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=12725c02600000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=162163c2600000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+5a6c4ec678a0c6ee84ba@xxxxxxxxxxxxxxxxxxxxxxxxx

==================================================================
BUG: KASAN: slab-out-of-bounds in strlen+0x79/0x90 lib/string.c:525
Read of size 1 at addr ffff8881d29bdf38 by task syz-executor201/1726

CPU: 1 PID: 1726 Comm: syz-executor201 Not tainted 5.3.0-rc2+ #25
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+0xca/0x13e lib/dump_stack.c:113
 print_address_description+0x6a/0x32c mm/kasan/report.c:351
 __kasan_report.cold+0x1a/0x33 mm/kasan/report.c:482
 kasan_report+0xe/0x12 mm/kasan/common.c:612
 strlen+0x79/0x90 lib/string.c:525
 strlen include/linux/string.h:281 [inline]
 hidraw_ioctl+0x245/0xae0 drivers/hid/hidraw.c:446
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:509 [inline]
 do_vfs_ioctl+0xd2d/0x1330 fs/ioctl.c:696
 ksys_ioctl+0x9b/0xc0 fs/ioctl.c:713
 __do_sys_ioctl fs/ioctl.c:720 [inline]
 __se_sys_ioctl fs/ioctl.c:718 [inline]
 __x64_sys_ioctl+0x6f/0xb0 fs/ioctl.c:718
 do_syscall_64+0xb7/0x580 arch/x86/entry/common.c:296
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x445679
Code: e8 5c ad 02 00 48 83 c4 18 c3 0f 1f 80 00 00 00 00 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 9b cd fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007ffc8514f3a8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 0000000000445679
RDX: 0000000000000000 RSI: 0000000080404805 RDI: 0000000000000004
RBP: 00000000006d0018 R08: 000000000000000b R09: 00000000004002e0
R10: 000000000000000f R11: 0000000000000246 R12: 00000000004028a0
R13: 0000000000402930 R14: 0000000000000000 R15: 0000000000000000

Allocated by task 0:
(stack is not available)

Freed by task 0:
(stack is not available)

The buggy address belongs to the object at ffff8881d29bde60
 which belongs to the cache shmem_inode_cache of size 1168
The buggy address is located 216 bytes inside of
 1168-byte region [ffff8881d29bde60, ffff8881d29be2f0)
The buggy address belongs to the page:
page:ffffea00074a6f00 refcount:1 mapcount:0 mapping:ffff8881da115180  
index:0x0 compound_mapcount: 0
flags: 0x200000000010200(slab|head)
raw: 0200000000010200 dead000000000100 dead000000000122 ffff8881da115180
raw: 0000000000000000 00000000800c000c 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8881d29bde00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8881d29bde80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> ffff8881d29bdf00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
                                        ^
 ffff8881d29bdf80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8881d29be000: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================