Re: [PATCH] usbip: usbip_host: fix bad unlock balance during stub_probe()

[Greg KH <gregkh@linuxfoundation.org>]

On Tue, May 15, 2018 at 05:57:23PM -0600, Shuah Khan (Samsung OSG) wrote:
> stub_probe() calls put_busid_priv() in an error path when device isn't
> found in the busid_table. Fix it by making put_busid_priv() safe to be
> called with null struct bus_id_priv pointer.
> 
> This problem happens when "usbip bind" is run without loading usbip_host
> driver and then running modprobe. The first failed bind attempt unbinds
> the device from the original driver and when usbip_host is modprobed,
> stub_probe() runs and doesn't find the device in its busid table and calls
> put_busid_priv(0 with null bus_id_priv pointer.
> 
> usbip-host 3-10.2: 3-10.2 is not in match_busid table...  skip!
> 
> [  367.359679] =====================================
> [  367.359681] WARNING: bad unlock balance detected!
> [  367.359683] 4.17.0-rc4+ #5 Not tainted
> [  367.359685] -------------------------------------
> [  367.359688] modprobe/2768 is trying to release lock (
> [  367.359689]
> ==================================================================
> [  367.359696] BUG: KASAN: null-ptr-deref in
> print_unlock_imbalance_bug+0x99/0x110
> [  367.359699] Read of size 8 at addr 0000000000000058 by task
> modprobe/2768

Minor nit, no need to line-wrap this.

> [  367.359705] CPU: 4 PID: 2768 Comm: modprobe Not tainted 4.17.0-rc4+ #5
> 
> Fixes: 22076557b07c ("usbip: usbip_host: fix NULL-ptr deref and
> use-after-free errors") in usb-linus

Nor this, and the extra blank line isn't needed here either.  I'll fix
it up by hand when I queue this up later today, thanks.

greg k-h