Re: BUG: bad usercopy in ld_usb_read

[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=17cf0b16600000
kernel config:  https://syzkaller.appspot.com/x/.config?x=cfa2c18fb6a8068e
dashboard link: https://syzkaller.appspot.com/bug?extid=45b2f40f0778cfa7634e
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=151bab16600000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=148f8cd2600000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+45b2f40f0778cfa7634e@xxxxxxxxxxxxxxxxxxxxxxxxx

ldusb 4-1:0.28: Read buffer overflow, -3222596215958809898 bytes dropped
usercopy: Kernel memory exposure attempt detected from process stack  
(offset 0, size 2147479552)!
------------[ cut here ]------------
kernel BUG at mm/usercopy.c:98!
invalid opcode: 0000 [#1] SMP KASAN
CPU: 1 PID: 2023 Comm: syz-executor861 Not tainted 5.3.0-rc2+ #25
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
RIP: 0010:usercopy_abort+0xb9/0xbb mm/usercopy.c:98
Code: e8 c1 f7 d6 ff 49 89 d9 4d 89 e8 4c 89 e1 41 56 48 89 ee 48 c7 c7 e0  
f3 cd 85 ff 74 24 08 41 57 48 8b 54 24 20 e8 15 98 c1 ff <0f> 0b e8 95 f7  
d6 ff e8 80 9f fd ff 8b 54 24 04 49 89 d8 4c 89 e1
RSP: 0018:ffff8881cbda7c40 EFLAGS: 00010282
RAX: 0000000000000061 RBX: ffffffff85cdf100 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff8128a0fd RDI: ffffed10397b4f7a
RBP: ffffffff85cdf2c0 R08: 0000000000000061 R09: fffffbfff11acda1
R10: fffffbfff11acda0 R11: ffffffff88d66d07 R12: ffffffff85cdf4e0
R13: ffffffff85cdf100 R14: 000000007ffff000 R15: ffffffff85cdf100
FS:  00007f10bb76a700(0000) GS:ffff8881db300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f7135a49000 CR3: 00000001d20e8000 CR4: 00000000001406e0
Call Trace:
 __check_object_size mm/usercopy.c:276 [inline]
 __check_object_size.cold+0x91/0xba mm/usercopy.c:250
 check_object_size include/linux/thread_info.h:119 [inline]
 check_copy_size include/linux/thread_info.h:150 [inline]
 copy_to_user include/linux/uaccess.h:151 [inline]
 ld_usb_read+0x304/0x780 drivers/usb/misc/ldusb.c:495
 __vfs_read+0x76/0x100 fs/read_write.c:425
 vfs_read+0x1ea/0x430 fs/read_write.c:461
 ksys_read+0x1e8/0x250 fs/read_write.c:587
 do_syscall_64+0xb7/0x580 arch/x86/entry/common.c:296
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x446e19
Code: e8 ec e7 ff ff 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 3b 07 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f10bb769d98 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
RAX: ffffffffffffffda RBX: 00000000006dbc38 RCX: 0000000000446e19
RDX: 00000000ffffffbc RSI: 0000000020000040 RDI: 0000000000000004
RBP: 00000000006dbc30 R08: 0000000000000000 R09: 0000000000000000
R10: 000000000000000f R11: 0000000000000246 R12: 00000000006dbc3c
R13: 0001002402090100 R14: 000048c920200f11 R15: 08983baa00000112
Modules linked in:
---[ end trace 93f3613883c53c00 ]---
RIP: 0010:usercopy_abort+0xb9/0xbb mm/usercopy.c:98
Code: e8 c1 f7 d6 ff 49 89 d9 4d 89 e8 4c 89 e1 41 56 48 89 ee 48 c7 c7 e0  
f3 cd 85 ff 74 24 08 41 57 48 8b 54 24 20 e8 15 98 c1 ff <0f> 0b e8 95 f7  
d6 ff e8 80 9f fd ff 8b 54 24 04 49 89 d8 4c 89 e1
RSP: 0018:ffff8881cbda7c40 EFLAGS: 00010282
RAX: 0000000000000061 RBX: ffffffff85cdf100 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff8128a0fd RDI: ffffed10397b4f7a
RBP: ffffffff85cdf2c0 R08: 0000000000000061 R09: fffffbfff11acda1
R10: fffffbfff11acda0 R11: ffffffff88d66d07 R12: ffffffff85cdf4e0
R13: ffffffff85cdf100 R14: 000000007ffff000 R15: ffffffff85cdf100
FS:  00007f10bb76a700(0000) GS:ffff8881db300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f7135a49000 CR3: 00000001d20e8000 CR4: 00000000001406e0