linux-kernel - [PATCH V2] clk: fix a panic error caused by accessing NULL pointer

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Date:   Tue, 21 Nov 2017 17:24:38 +0800
From:   Chunyan Zhang <chunyan.zhang@...eadtrum.com>
To:     Stephen Boyd <sboyd@...eaurora.org>,
        Michael Turquette <mturquette@...libre.com>
CC:     <linux-clk@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        Cai Li <cai.li@...eadtrum.com>,
        Orson Zhai <orson.zhai@...eadtrum.com>,
        Chunyan Zhang <zhang.lyra@...il.com>
Subject: [PATCH V2] clk: fix a panic error caused by accessing NULL pointer

From: Cai Li <cai.li@...eadtrum.com>

In some cases the clock parent would be set NULL when doing re-parent,
it will cause a NULL pointer accessing if clk_set trace event is
enabled.

This patch sets the parent as "none" if the input parameter is NULL.

Fixes: dfc202ead312 (clk: Add tracepoints for hardware operations)
Signed-off-by: Cai Li <cai.li@...eadtrum.com>
Signed-off-by: Chunyan Zhang <chunyan.zhang@...eadtrum.com>
---
Changes from v1:
Revised the tracepoint code instead of clk driver.
---
 include/trace/events/clk.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/trace/events/clk.h b/include/trace/events/clk.h
index 7586072..2cd4493 100644
--- a/include/trace/events/clk.h
+++ b/include/trace/events/clk.h
@@ -134,12 +134,12 @@ DECLARE_EVENT_CLASS(clk_parent,
 
 	TP_STRUCT__entry(
 		__string(        name,           core->name                )
-		__string(        pname,          parent->name              )
+		__string(        pname, parent ? parent->name : "none"     )
 	),
 
 	TP_fast_assign(
 		__assign_str(name, core->name);
-		__assign_str(pname, parent->name);
+		__assign_str(pname, parent ? parent->name : "none");
 	),
 
 	TP_printk("%s %s", __get_str(name), __get_str(pname))
-- 
2.7.4