From: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
This patch has been added to the 3.12 stable tree. If you have any
objections, please let us know.
===============
commit 3df48c981d5a9610e02e9270b1bc4274fb536710 upstream.
In commit 330a1eb "Core EBB support for 64-bit book3s" I messed up
clear_task_ebb(). It clears some but not all of the task's Event Based
Branch (EBB) registers when we duplicate a task struct.
That allows a child task to observe the EBBHR & EBBRR of its parent,
which it should not be able to do.
Fix it by clearing EBBHR & EBBRR.
Signed-off-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Signed-off-by: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Jiri Slaby <jslaby@xxxxxxx>
---
arch/powerpc/include/asm/switch_to.h | 2 ++
1 file changed, 2 insertions(+)
diff --git a/arch/powerpc/include/asm/switch_to.h b/arch/powerpc/include/asm/switch_to.h
index 2be5618cdec6..06d63a3c1a88 100644
--- a/arch/powerpc/include/asm/switch_to.h
+++ b/arch/powerpc/include/asm/switch_to.h
@@ -85,6 +85,8 @@ static inline void clear_task_ebb(struct task_struct *t)
{
#ifdef CONFIG_PPC_BOOK3S_64
/* EBB perf events are not inherited, so clear all EBB state. */
+ t->thread.ebbrr = 0;
+ t->thread.ebbhr = 0;
t->thread.bescr = 0;
t->thread.mmcr2 = 0;
t->thread.mmcr0 = 0;
--
2.0.0
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