This is a note to let you know that I've just added the patch titled
powerpc/mce: fix off by one errors in mce event handling
to the 4.0-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:
powerpc-mce-fix-off-by-one-errors-in-mce-event-handling.patch
and it can be found in the queue-4.0 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From ffb2d78eca08a1451137583d4e435aecfd6af809 Mon Sep 17 00:00:00 2001
From: Daniel Axtens <dja@xxxxxxxxxx>
Date: Tue, 12 May 2015 13:23:59 +1000
Subject: powerpc/mce: fix off by one errors in mce event handling
From: Daniel Axtens <dja@xxxxxxxxxx>
commit ffb2d78eca08a1451137583d4e435aecfd6af809 upstream.
Before 69111bac42f5 ("powerpc: Replace __get_cpu_var uses"), in
save_mce_event, index got the value of mce_nest_count, and
mce_nest_count was incremented *after* index was set.
However, that patch changed the behaviour so that mce_nest count was
incremented *before* setting index.
This causes an off-by-one error, as get_mce_event sets index as
mce_nest_count - 1 before reading mce_event. Thus get_mce_event reads
bogus data, causing warnings like
"Machine Check Exception, Unknown event version 0 !"
and breaking MCEs handling.
Restore the old behaviour and unbreak MCE handling by subtracting one
from the newly incremented value.
The same broken change occured in machine_check_queue_event (which set
a queue read by machine_check_process_queued_event). Fix that too,
unbreaking printing of MCE information.
Fixes: 69111bac42f5 ("powerpc: Replace __get_cpu_var uses")
CC: Mahesh Salgaonkar <mahesh@xxxxxxxxxxxxxxxxxx>
CC: Christoph Lameter <cl@xxxxxxxxx>
Signed-off-by: Daniel Axtens <dja@xxxxxxxxxx>
Signed-off-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/powerpc/kernel/mce.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
--- a/arch/powerpc/kernel/mce.c
+++ b/arch/powerpc/kernel/mce.c
@@ -73,7 +73,7 @@ void save_mce_event(struct pt_regs *regs
uint64_t nip, uint64_t addr)
{
uint64_t srr1;
- int index = __this_cpu_inc_return(mce_nest_count);
+ int index = __this_cpu_inc_return(mce_nest_count) - 1;
struct machine_check_event *mce = this_cpu_ptr(&mce_event[index]);
/*
@@ -184,7 +184,7 @@ void machine_check_queue_event(void)
if (!get_mce_event(&evt, MCE_EVENT_RELEASE))
return;
- index = __this_cpu_inc_return(mce_queue_count);
+ index = __this_cpu_inc_return(mce_queue_count) - 1;
/* If queue is full, just return for now. */
if (index >= MAX_MC_EVT) {
__this_cpu_dec(mce_queue_count);
Patches currently in stable-queue which might be from dja@xxxxxxxxxx are
queue-4.0/powerpc-mce-fix-off-by-one-errors-in-mce-event-handling.patch
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