This is a note to let you know that I've just added the patch titled
parisc: fix interruption handler to respect pagefault_disable()
to the 3.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
parisc-fix-interruption-handler-to-respect-pagefault_disable.patch
and it can be found in the queue-3.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 59b33f148cc08fb33cbe823fca1e34f7f023765e Mon Sep 17 00:00:00 2001
From: Helge Deller <deller@xxxxxx>
Date: Tue, 1 Oct 2013 21:54:46 +0200
Subject: parisc: fix interruption handler to respect pagefault_disable()
From: Helge Deller <deller@xxxxxx>
commit 59b33f148cc08fb33cbe823fca1e34f7f023765e 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: Helge Deller <deller@xxxxxx>
Signed-off-by: John David Anglin <dave.anglin@xxxxxxxx>
Signed-off-by: Helge Deller <deller@xxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/parisc/kernel/traps.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
--- a/arch/parisc/kernel/traps.c
+++ b/arch/parisc/kernel/traps.c
@@ -810,14 +810,14 @@ void notrace handle_interruption(int cod
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);
-
}
}
Patches currently in stable-queue which might be from deller@xxxxxx are
queue-3.4/parisc-fix-interruption-handler-to-respect-pagefault_disable.patch
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