Re: BUG: bad usercopy in ld_usb_read

[Johan Hovold]

On Mon, Aug 12, 2019 at 02:06:08PM +0200, Andrey Konovalov wrote:
> On Thu, Aug 8, 2019 at 2:38 PM syzbot
> <syzbot+45b2f40f0778cfa7634e@xxxxxxxxxxxxxxxxxxxxxxxxx> 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@xxxxxxxxxxxxxxxxxxxxxxxxx
> >
> > 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

This was a different bug. Mark as dup of the latest report:

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

Johan