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SubjectKASAN: slab-out-of-bounds Read in ld_usb_read (3)
From
Hello,

syzbot found the following crash on:

HEAD commit: 22be26f7 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=14f6dc5f600000
kernel config: https://syzkaller.appspot.com/x/.config?x=387eccb7ac68ec5
dashboard link: https://syzkaller.appspot.com/bug?extid=6fe95b826644f7f12b0b
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=102c3227600000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=12a503a0e00000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+6fe95b826644f7f12b0b@syzkaller.appspotmail.com

ldusb 1-1:0.28: Read buffer overflow, -131383859965943 bytes dropped
==================================================================
BUG: KASAN: slab-out-of-bounds in _copy_to_user+0x124/0x150
lib/usercopy.c:28
Read of size 102391 at addr ffff8881cfb40008 by task syz-executor372/1737

CPU: 0 PID: 1737 Comm: syz-executor372 Not tainted 5.4.0-rc3+ #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.constprop.0+0x36/0x50 mm/kasan/report.c:374
__kasan_report.cold+0x1a/0x33 mm/kasan/report.c:506
kasan_report+0xe/0x20 mm/kasan/common.c:634
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:28
copy_to_user include/linux/uaccess.h:152 [inline]
ld_usb_read+0x329/0x760 drivers/usb/misc/ldusb.c:492
__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:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x4421d9
Code: e8 7c 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 bb 07 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007ffc08eb0888 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
RAX: ffffffffffffffda RBX: 00007ffc08eb0ae0 RCX: 00000000004421d9
RDX: 0000000000018ff7 RSI: 0000000020000a80 RDI: 0000000000000004
RBP: 0000000000000000 R08: 000000000000000f R09: 0000000000402eb0
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000402eb0 R14: 0000000000000000 R15: 0000000000000000

The buggy address belongs to the page:
page:ffffea00073ed000 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:
ffff8881cfb55500: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff8881cfb55580: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> ffff8881cfb55600: fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe
^
ffff8881cfb55680: fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe
ffff8881cfb55700: 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@googlegroups.com.

syzbot will keep track of this bug report. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
syzbot can test patches for this bug, for details see:
https://goo.gl/tpsmEJ#testing-patches

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