Re: BUG: bad usercopy in ld_usb_read (3)

[Johan Hovold]

On Wed, Oct 16, 2019 at 06:42:11PM -0700, syzbot wrote:
> 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=1756ff77600000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=387eccb7ac68ec5
> dashboard link: https://syzkaller.appspot.com/bug?extid=acee996f6938b9ded381
> 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+acee996f6938b9ded381@xxxxxxxxxxxxxxxxxxxxxxxxx
> 
> ldusb 5-1:0.28: Read buffer overflow, 177886378725897 bytes dropped
> usercopy: Kernel memory exposure attempt detected from process stack  
> (offset 0, size 2147479552)!
> ------------[ cut here ]------------
> kernel BUG at mm/usercopy.c:99!
> invalid opcode: 0000 [#1] SMP KASAN
> CPU: 1 PID: 6543 Comm: syz-executor.5 Not tainted 5.4.0-rc3+ #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
> Google 01/01/2011
> RIP: 0010:usercopy_abort+0xb9/0xbb mm/usercopy.c:99
> Code: e8 32 51 d6 ff 49 89 d9 4d 89 e8 4c 89 e1 41 56 48 89 ee 48 c7 c7 40  
> d9 cd 85 ff 74 24 08 41 57 48 8b 54 24 20 e8 46 e3 c0 ff <0f> 0b e8 06 51  
> d6 ff e8 31 8b fd ff 8b 54 24 04 49 89 d8 4c 89 e1
> RSP: 0018:ffff8881d35f7c58 EFLAGS: 00010282
> RAX: 0000000000000061 RBX: ffffffff85cdd660 RCX: 0000000000000000
> RDX: 0000000000000000 RSI: ffffffff8128bcbd RDI: ffffed103a6bef7d
> RBP: ffffffff85cdd820 R08: 0000000000000061 R09: fffffbfff11b23be
> R10: fffffbfff11b23bd R11: ffffffff88d91def R12: ffffffff85cdda40
> R13: ffffffff85cdd660 R14: 000000007ffff000 R15: ffffffff85cdd660
> FS:  00007fb330338700(0000) GS:ffff8881db300000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007f07cea47000 CR3: 00000001cc11e000 CR4: 00000000001406e0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
>   __check_object_size mm/usercopy.c:282 [inline]
>   __check_object_size.cold+0x91/0xbb mm/usercopy.c:256
>   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+0x31a/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: 0033:0x459a59
> 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:00007fb330337c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
> RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000459a59
> RDX: 00000000ffffffad RSI: 0000000020003200 RDI: 0000000000000004
> RBP: 000000000075bfc8 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 00007fb3303386d4
> R13: 00000000004c7120 R14: 00000000004dcae8 R15: 00000000ffffffff
> Modules linked in:
> ---[ end trace 0fa22c64036b6ebe ]---
> RIP: 0010:usercopy_abort+0xb9/0xbb mm/usercopy.c:99
> Code: e8 32 51 d6 ff 49 89 d9 4d 89 e8 4c 89 e1 41 56 48 89 ee 48 c7 c7 40  
> d9 cd 85 ff 74 24 08 41 57 48 8b 54 24 20 e8 46 e3 c0 ff <0f> 0b e8 06 51  
> d6 ff e8 31 8b fd ff 8b 54 24 04 49 89 d8 4c 89 e1
> RSP: 0018:ffff8881d35f7c58 EFLAGS: 00010282
> RAX: 0000000000000061 RBX: ffffffff85cdd660 RCX: 0000000000000000
> RDX: 0000000000000000 RSI: ffffffff8128bcbd RDI: ffffed103a6bef7d
> RBP: ffffffff85cdd820 R08: 0000000000000061 R09: fffffbfff11b23be
> R10: fffffbfff11b23bd R11: ffffffff88d91def R12: ffffffff85cdda40
> R13: ffffffff85cdd660 R14: 000000007ffff000 R15: ffffffff85cdd660
> FS:  00007fb330338700(0000) GS:ffff8881db300000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007f07cea47000 CR3: 00000001cc11e000 CR4: 00000000001406e0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400

#syz dup: KASAN: slab-out-of-bounds Read in ld_usb_read (3)

Fix under way.

Johan