From: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Date: Fri, 6 Jul 2012 01:30:58 +0000 (+0000)
Subject: powerpc/hw_breakpoints: Fix incorrect pointer access
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=ac84aa2b3b9b791eac45174d1966d5fdf3bbba1c;p=linux-beck.git

powerpc/hw_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@linux.vnet.ibm.com>
Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
---

diff --git a/arch/powerpc/kernel/hw_breakpoint.c b/arch/powerpc/kernel/hw_breakpoint.c
index 2bc0584be81c..f3a82dde61db 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;
 }