Re: BUG: bad usercopy in ld_usb_read

[Andrey Konovalov <andreyknvl@google.com>]

On Thu, Aug 8, 2019 at 2:38 PM syzbot
<syzbot+45b2f40f0778cfa7634e@syzkaller.appspotmail.com> wrote:
>
> 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=13aeaece600000
> 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)
>
> 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+45b2f40f0778cfa7634e@syzkaller.appspotmail.com
>
> ldusb 6-1:0.124: Read buffer overflow, -131383996186150 bytes dropped
> usercopy: Kernel memory exposure attempt detected from SLUB
> object 'kmalloc-2k' (offset 8, size 65062)!
> ------------[ cut here ]------------
> kernel BUG at mm/usercopy.c:98!
> invalid opcode: 0000 [#1] SMP KASAN
> CPU: 0 PID: 15185 Comm: syz-executor.2 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:ffff8881ccb3fc38 EFLAGS: 00010286
> RAX: 0000000000000067 RBX: ffffffff86a659d4 RCX: 0000000000000000
> RDX: 0000000000000000 RSI: ffffffff8128a0fd RDI: ffffed1039967f79
> RBP: ffffffff85cdf2c0 R08: 0000000000000067 R09: fffffbfff11acdaa
> R10: fffffbfff11acda9 R11: ffffffff88d66d4f R12: ffffffff86a696e8
> R13: ffffffff85cdf180 R14: 000000000000fe26 R15: ffffffff85cdf140
> FS:  00007ff6daf91700(0000) GS:ffff8881db200000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007f1de6600000 CR3: 00000001ca554000 CR4: 00000000001406f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
>   __check_heap_object+0xdd/0x110 mm/slub.c:3914
>   check_heap_object mm/usercopy.c:234 [inline]
>   __check_object_size mm/usercopy.c:280 [inline]
>   __check_object_size+0x32d/0x39b 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

#syz dup: KASAN: use-after-free Read in ld_usb_release

>   __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: 0033:0x459829
> 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:00007ff6daf90c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
> RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000459829
> RDX: 000000000000fe26 RSI: 00000000200000c0 RDI: 0000000000000003
> RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 00007ff6daf916d4
> R13: 00000000004c6c73 R14: 00000000004dbee8 R15: 00000000ffffffff
> Modules linked in:
> ---[ end trace 4fe8dba032d24ceb ]---
> 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:ffff8881ccb3fc38 EFLAGS: 00010286
> RAX: 0000000000000067 RBX: ffffffff86a659d4 RCX: 0000000000000000
> RDX: 0000000000000000 RSI: ffffffff8128a0fd RDI: ffffed1039967f79
> RBP: ffffffff85cdf2c0 R08: 0000000000000067 R09: fffffbfff11acdaa
> R10: fffffbfff11acda9 R11: ffffffff88d66d4f R12: ffffffff86a696e8
> R13: ffffffff85cdf180 R14: 000000000000fe26 R15: ffffffff85cdf140
> FS:  00007ff6daf91700(0000) GS:ffff8881db200000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007f1de6600000 CR3: 00000001ca554000 CR4: 00000000001406f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
>
>
> ---
> 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.