Commit 77587e89 authored by Helge Deller's avatar Helge Deller Committed by Greg Kroah-Hartman

parisc: fix interruption handler to respect pagefault_disable()

commit 59b33f14 upstream.

Running an "echo t > /proc/sysrq-trigger" crashes the parisc kernel.  The
problem is, that in print_worker_info() we try to read the workqueue info via
the probe_kernel_read() functions which use pagefault_disable() to avoid
crashes like this:
    probe_kernel_read(&pwq, &worker->current_pwq, sizeof(pwq));
    probe_kernel_read(&wq, &pwq->wq, sizeof(wq));
    probe_kernel_read(name, wq->name, sizeof(name) - 1);

The problem here is, that the first probe_kernel_read(&pwq) might return zero
in pwq and as such the following probe_kernel_reads() try to access contents of
the page zero which is read protected and generate a kernel segfault.

With this patch we fix the interruption handler to call parisc_terminate()
directly only if pagefault_disable() was not called (in which case
preempt_count()==0).  Otherwise we hand over to the pagefault handler which
will try to look up the faulting address in the fixup tables.
Signed-off-by: default avatarHelge Deller <deller@gmx.de>
Signed-off-by: default avatarJohn David Anglin  <dave.anglin@bell.net>
Signed-off-by: default avatarHelge Deller <deller@gmx.de>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 40ee05de
......@@ -805,14 +805,14 @@ void notrace handle_interruption(int code, struct pt_regs *regs)
else {
/*
* The kernel should never fault on its own address space.
* The kernel should never fault on its own address space,
* unless pagefault_disable() was called before.
*/
if (fault_space == 0)
if (fault_space == 0 && !in_atomic())
{
pdc_chassis_send_status(PDC_CHASSIS_DIRECT_PANIC);
parisc_terminate("Kernel Fault", regs, code, fault_address);
}
}
......
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