linux-kernel - [PATCH] PM: declare __tracedata symbols as char[] rather than char

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Message-Id: <1453687732-1602-1-git-send-email-ebiggers3@gmail.com>
Date:	Sun, 24 Jan 2016 20:08:52 -0600
From:	Eric Biggers <ebiggers3@...il.com>
To:	rjw@...ysocki.net
Cc:	linux-pm@...r.kernel.org, pavel@....cz, len.brown@...el.com,
	gregkh@...uxfoundation.org, linux-kernel@...r.kernel.org,
	Eric Biggers <ebiggers3@...il.com>
Subject: [PATCH] PM: declare __tracedata symbols as char[] rather than char

Accessing more than one byte from a symbol declared simply 'char' is undefined
behavior, as reported by UBSAN:

	UBSAN: Undefined behaviour in drivers/base/power/trace.c:178:18
	load of address ffffffff8203fc78 with insufficient space
	for an object of type 'char'

Avoid this by declaring the symbols as arrays.

Signed-off-by: Eric Biggers <ebiggers3@...il.com>
---
 drivers/base/power/trace.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/base/power/trace.c b/drivers/base/power/trace.c
index a311cfa..a697579 100644
--- a/drivers/base/power/trace.c
+++ b/drivers/base/power/trace.c
@@ -166,14 +166,14 @@ void generate_pm_trace(const void *tracedata, unsigned int user)
 }
 EXPORT_SYMBOL(generate_pm_trace);
 
-extern char __tracedata_start, __tracedata_end;
+extern char __tracedata_start[], __tracedata_end[];
 static int show_file_hash(unsigned int value)
 {
 	int match;
 	char *tracedata;
 
 	match = 0;
-	for (tracedata = &__tracedata_start ; tracedata < &__tracedata_end ;
+	for (tracedata = __tracedata_start ; tracedata < __tracedata_end ;
 			tracedata += 2 + sizeof(unsigned long)) {
 		unsigned short lineno = *(unsigned short *)tracedata;
 		const char *file = *(const char **)(tracedata + 2);
-- 
2.7.0