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usbip: usbip_host: fix bad unlock balance during stub_probe()

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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

[  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
Signed-off-by: Shuah Khan (Samsung OSG) <shuah@kernel.org>
Cc: stable <stable@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Shuah Khan (Samsung OSG) 2018-05-15 17:57:23 -06:00 committed by Greg Kroah-Hartman
parent 22076557b0
commit c171654caa
1 changed files with 2 additions and 1 deletions
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3
drivers/usb/usbip/stub_main.c
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@ -82,7 +82,8 @@ struct bus_id_priv *get_busid_priv(const char *busid)
void put_busid_priv(struct bus_id_priv *bid)
{
spin_unlock(&bid->busid_lock);
if (bid)
spin_unlock(&bid->busid_lock);
}
static int add_match_busid(char *busid)