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Message-ID: <20120706113058.8600.30142.stgit@localhost.localdomain>
Date:	Fri, 06 Jul 2012 17:00:58 +0530
From:	"Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>
To:	fweisbec@...il.com, benh@...nel.crashing.org, paulus@...ba.org,
	prasad.krishnan@...il.com
Cc:	linuxppc-dev@...abs.org, linux-kernel@...r.kernel.org,
	emachado@...ux.vnet.ibm.com
Subject: [PATCH] PPC Hardware Breakpoints: Fix incorrect pointer access

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 <emachado@...ux.vnet.ibm.com>
Signed-off-by: Naveen N. Rao <naveen.n.rao@...ux.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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