KASAN: slab-out-of-bounds Read in ld_usb_read

[syzbot]

Hello,

syzbot found 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=162aac02600000
kernel config:  https://syzkaller.appspot.com/x/.config?x=cfa2c18fb6a8068e
dashboard link: https://syzkaller.appspot.com/bug?extid=ba00d6a2a24df57a94ca
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1123edc2600000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=16079d2c600000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+ba00d6a2a24df57a94ca@xxxxxxxxxxxxxxxxxxxxxxxxx

ldusb 1-1:0.28: Read buffer overflow, -131386046930688 bytes dropped
==================================================================
BUG: KASAN: slab-out-of-bounds in _copy_to_user+0x124/0x150  
lib/usercopy.c:27
Read of size 2147479552 at addr ffff8881cd580008 by task  
syz-executor268/1890

CPU: 0 PID: 1890 Comm: syz-executor268 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
 check_memory_region_inline mm/kasan/generic.c:185 [inline]
 check_memory_region+0x128/0x190 mm/kasan/generic.c:192
 _copy_to_user+0x124/0x150 lib/usercopy.c:27
 copy_to_user include/linux/uaccess.h:152 [inline]
 ld_usb_read+0x31a/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: 0033:0x441c49
Code: e8 8c e8 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 cb 08 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007ffd920003d8 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 0000000000441c49
RDX: 00000000fffffd68 RSI: 0000000020000100 RDI: 0000000000000004
RBP: 00000000000305b5 R08: 000000000000000f R09: 0000000000402a30
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000004029a0
R13: 0000000000402a30 R14: 0000000000000000 R15: 0000000000000000

The buggy address belongs to the page:
page:ffffea0007356000 refcount:1 mapcount:0 mapping:0000000000000000  
index:0x0 compound_mapcount: 0
flags: 0x200000000010000(head)
raw: 0200000000010000 dead000000000100 dead000000000122 0000000000000000
raw: 0000000000000000 0000000000000000 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8881cd595500: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff8881cd595580: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> ffff8881cd595600: fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe
                   ^
 ffff8881cd595680: fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe
 ffff8881cd595700: fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe
==================================================================


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