Re: [PATCH] usb: asix: Fix uninit-value in asix_mdio_write

[David Miller]

From: Phong Tran <tranmanphong@xxxxxxxxx>
Date: Thu,  7 Nov 2019 07:44:04 +0700

> The local variables use without initilization value.
> This fixes the syzbot report.
> 
> Reported-by: syzbot+7dc7c28d4577bbe55b10@xxxxxxxxxxxxxxxxxxxxxxxxx
> 
> Test result:
> 
> https://groups.google.com/d/msg/syzkaller-bugs/3H_n05x_sPU/sUoHhxgAAgAJ
> 
> Signed-off-by: Phong Tran <tranmanphong@xxxxxxxxx>

There are several more situations in this file where the data blob passed
to asix_read_cmd() is read without pre-initialization not checking the
return value from asix_read_cmd().

So, syzbot can see some of them but not all of them, yet all of them
are buggy and should be fixed.

These kinds of patches drive me absolutely crazy :-)

Really, one of two things needs to happen, either asix_read_cmd() clears
the incoming buffer unconditionally, or these call sites strictly must
check the return value always before accessing the buffer after the call.

I'm not applying this, sorry.