linux-kernel - [PATCH v2] mm/writeback: fix dereferencing NULL mapping->host

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Date:   Wed, 30 Nov 2022 16:23:02 +0800
From:   Andrew Yang <andrew.yang@...iatek.com>
To:     <rostedt@...dmis.org>
CC:     <andrew.yang@...iatek.com>, <casper.li@...iatek.com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>,
        <linux-mediatek@...ts.infradead.org>, <matthias.bgg@...il.com>,
        <mhiramat@...nel.org>
Subject: [PATCH v2] mm/writeback: fix dereferencing NULL mapping->host

From: "andrew.yang" <andrew.yang@...iatek.com>

Check before dereferencing mapping->host

Suggested-by: Steven Rostedt <rostedt@...dmis.org>
Signed-off-by: andrew.yang <andrew.yang@...iatek.com>
---
v2: add parenthesis
---
 include/trace/events/writeback.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/trace/events/writeback.h b/include/trace/events/writeback.h
index 86b2a82da546..54e353c9f919 100644
--- a/include/trace/events/writeback.h
+++ b/include/trace/events/writeback.h
@@ -68,7 +68,7 @@ DECLARE_EVENT_CLASS(writeback_folio_template,
 		strscpy_pad(__entry->name,
 			    bdi_dev_name(mapping ? inode_to_bdi(mapping->host) :
 					 NULL), 32);
-		__entry->ino = mapping ? mapping->host->i_ino : 0;
+		__entry->ino = (mapping && mapping->host) ? mapping->host->i_ino : 0;
 		__entry->index = folio->index;
 	),
 
-- 
2.18.0