If arch_validate_hwbkpt_settings() fails, bp->ctx won't be valid and the
kernel panics. Add a check to fix this.

Reported-by: Edjunior Barbosa Machado <emach...@linux.vnet.ibm.com>
Signed-off-by: Naveen N. Rao <naveen.n....@linux.vnet.ibm.com>
---
 arch/powerpc/kernel/hw_breakpoint.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/powerpc/kernel/hw_breakpoint.c 
b/arch/powerpc/kernel/hw_breakpoint.c
index 2bc0584..f3a82dd 100644
--- a/arch/powerpc/kernel/hw_breakpoint.c
+++ b/arch/powerpc/kernel/hw_breakpoint.c
@@ -111,7 +111,7 @@ void arch_unregister_hw_breakpoint(struct perf_event *bp)
         * and the single_step_dabr_instruction(), then cleanup the breakpoint
         * restoration variables to prevent dangling pointers.
         */
-       if (bp->ctx->task)
+       if (bp->ctx && bp->ctx->task)
                bp->ctx->task->thread.last_hit_ubp = NULL;
 }
 

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