can: mcp251x: fix deadlock if an interrupt occurs during mcp251x_open

In the Linux kernel, the following vulnerability has been resolved:

can: mcp251x: fix deadlock if an interrupt occurs during mcp251x_open

The mcp251x_hw_wake() function is called with the mpc_lock mutex held and

disables the interrupt handler so that no interrupts can be processed while

waking the device. If an interrupt has already occurred then waiting for

the interrupt handler to complete will deadlock because it will be trying

to acquire the same mutex.

CPU0 CPU1

---- ----

mcp251x_open()

mutex_lock(&priv->mcp_lock)

request_threaded_irq()

<interrupt>

mcp251x_can_ist()

mutex_lock(&priv->mcp_lock)

mcp251x_hw_wake()

disable_irq() <-- deadlock

Use disable_irq_nosync() instead because the interrupt handler does

everything while holding the mutex so it doesn't matter if it's still

running.