KASAN: slab-out-of-bounds Read in ld_usb_read (2)

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    f0df5c1b 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=1462f9a5600000
kernel config:  https://syzkaller.appspot.com/x/.config?x=5c6633fa4ed00be5
dashboard link: https://syzkaller.appspot.com/bug?extid=4a52dbcef08fddbc887e
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+4a52dbcef08fddbc887e@xxxxxxxxxxxxxxxxxxxxxxxxx

ldusb 3-1:0.98: Read buffer overflow, -2576376864 bytes dropped
==================================================================
BUG: KASAN: slab-out-of-bounds in _copy_to_user+0x124/0x150  
lib/usercopy.c:27
Read of size 536879616 at addr ffff8881ab680008 by task syz-executor.2/12817

CPU: 0 PID: 12817 Comm: syz-executor.2 Not tainted 5.3.0-rc7+ #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+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:618
 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: 0033:0x4598e9
Code: fd b7 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 cb b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fad75925c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00000000004598e9
RDX: 0000000020002200 RSI: 0000000020001200 RDI: 0000000000000004
RBP: 000000000075bfc8 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007fad759266d4
R13: 00000000004c6d1a R14: 00000000004dc0c0 R15: 00000000ffffffff

The buggy address belongs to the page:
page:ffffea0006ada000 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:
 ffff8881ab6a0300: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff8881ab6a0380: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> ffff8881ab6a0400: fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe
                   ^
 ffff8881ab6a0480: fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe
 ffff8881ab6a0500: fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe
==================================================================


---
This bug is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzkaller@xxxxxxxxxxxxxxxxx

syzbot will keep track of this bug report. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.