linux-kernel - [PATCH v3] regmap: fix alignment issue

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Message-ID: <20200529192538.GA28402@toerring.de>
Date:   Fri, 29 May 2020 21:25:38 +0200
From:   Jens Thoms Toerring <jt@...rring.de>
To:     Mark Brown <broonie@...nel.org>, linux-kernel@...r.kernel.org
Subject: [PATCH v3] regmap: fix alignment issue

The assembly and disassembly of data to be sent to or received from a
device invoke functions (regmap_format_XXX() and regmap_parse_XXX())
that extract or insert data items from or into a buffer, using
assignments. In some cases those functions are called with buffer
pointers with odd addresses. On architectures with strict alignment
requirements this results in a kernel crash for u16 and u32 values.
The assignments have been replaced by methods that take alignment
into consideration.

Signed-off-by: Jens Thoms Toerring <jt@...rring.de>
---
 drivers/base/regmap/regmap.c | 38 ++++++++++++++++++--------------------
 1 file changed, 18 insertions(+), 20 deletions(-)

diff --git a/drivers/base/regmap/regmap.c b/drivers/base/regmap/regmap.c
index 58cfb32..70f470e 100644
--- a/drivers/base/regmap/regmap.c
+++ b/drivers/base/regmap/regmap.c
@@ -193,15 +193,15 @@ static void regmap_format_8(void *buf, unsigned int val, unsigned int shift)
 
 static void regmap_format_16_be(void *buf, unsigned int val, unsigned int shift)
 {
-	__be16 *b = buf;
-
-	b[0] = cpu_to_be16(val << shift);
+	put_unaligned_be16(val << shift, buf);
 }
 
 static void regmap_format_16_native(void *buf, unsigned int val,
 				    unsigned int shift)
 {
-	*(u16 *)buf = val << shift;
+	u16 v = val << shift;
+
+	memcpy(buf, &v, sizeof(v));
 }
 
 static void regmap_format_24(void *buf, unsigned int val, unsigned int shift)
@@ -217,15 +217,15 @@ static void regmap_format_24(void *buf, unsigned int val, unsigned int shift)
 
 static void regmap_format_32_be(void *buf, unsigned int val, unsigned int shift)
 {
-	__be32 *b = buf;
-
-	b[0] = cpu_to_be32(val << shift);
+	put_unaligned_be32(val << shift, buf);
 }
 
 static void regmap_format_32_native(void *buf, unsigned int val,
 				    unsigned int shift)
 {
-	*(u32 *)buf = val << shift;
+	u32 = val << shift;
+
+	memcpy(buf, &v, sizeof(v));
 }
 
 static unsigned int regmap_parse_8(void *buf)
@@ -237,16 +237,15 @@ static unsigned int regmap_parse_8(void *buf)
 
 static unsigned int regmap_parse_16_be(void *buf)
 {
-	__be16 *b = buf;
-
-	b[0] = be16_to_cpu(b[0]);
-
-	return b[0];
+	return get_unaligned_be16(buf);
 }
 
 static unsigned int regmap_parse_16_native(void *buf)
 {
-	return *(u16 *)buf;
+	u16 v;
+
+	memcpy(&v, buf, sizeof(v));
+	return v;
 }
 
 static unsigned int regmap_parse_24(void *buf)
@@ -261,17 +260,15 @@ static unsigned int regmap_parse_24(void *buf)
 
 static unsigned int regmap_parse_32_be(void *buf)
 {
-	__be32 *b = buf;
-
-	b[0] = be32_to_cpu(b[0]);
-
-	return b[0];
+	return get_unaligned_be32(buf);
 }
 
 static unsigned int regmap_parse_32_native(void *buf)
 {
-	return *(u32 *)buf;
+	u32 v;
+
+	memcpy(&v, buf, sizeof(v));
+	return v;
 }
 
 static void regmap_lock_mutex(void *__map)
-- 
1.9.1