Patch "regmap: Fix possible shift overflow in regmap_field_init()" has been added to the 4.0-stable tree

Patch "regmap: Fix possible shift overflow in regmap_field_init()" has been added to the 4.0-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    regmap: Fix possible shift overflow in regmap_field_init()

to the 4.0-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     regmap-fix-possible-shift-overflow-in-regmap_field_init.patch
and it can be found in the queue-4.0 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 921cc29473a0d7c109105c1876ddb432f4a4be7d Mon Sep 17 00:00:00 2001
From: Maxime Coquelin <maxime.coquelin@st.com>
Date: Tue, 16 Jun 2015 13:53:19 +0200
Subject: regmap: Fix possible shift overflow in regmap_field_init()

From: Maxime Coquelin <maxime.coquelin@st.com>

commit 921cc29473a0d7c109105c1876ddb432f4a4be7d upstream.

The way the mask is generated in regmap_field_init() is wrong.
Indeed, a field initialized with msb = 31 and lsb = 0 provokes a shift
overflow while calculating the mask field.

On some 32 bits architectures, such as x86, the generated mask is 0,
instead of the expected 0xffffffff.

This patch uses GENMASK() to fix the problem, as this macro is already safe
regarding shift overflow.

Signed-off-by: Maxime Coquelin <maxime.coquelin@st.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/base/regmap/regmap.c |    3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

--- a/drivers/base/regmap/regmap.c
+++ b/drivers/base/regmap/regmap.c
@@ -945,11 +945,10 @@ EXPORT_SYMBOL_GPL(devm_regmap_init);
 static void regmap_field_init(struct regmap_field *rm_field,
 	struct regmap *regmap, struct reg_field reg_field)
 {
-	int field_bits = reg_field.msb - reg_field.lsb + 1;
 	rm_field->regmap = regmap;
 	rm_field->reg = reg_field.reg;
 	rm_field->shift = reg_field.lsb;
-	rm_field->mask = ((BIT(field_bits) - 1) << reg_field.lsb);
+	rm_field->mask = GENMASK(reg_field.msb, reg_field.lsb);
 	rm_field->id_size = reg_field.id_size;
 	rm_field->id_offset = reg_field.id_offset;
 }


Patches currently in stable-queue which might be from maxime.coquelin@st.com are

queue-4.0/regmap-fix-possible-shift-overflow-in-regmap_field_init.patch