regmap: Fix possible shift overflow in regmap_field_init()

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>
Cc: stable@vger.kernel.org

diff --git a/drivers/base/regmap/regmap.c b/drivers/base/regmap/regmap.c
index 6273ff072f3eaa4cbd777b1a4f41fb3cf533a42a..e5194f698d66e9ad2dc9cbd3a554b2b5a1c1b4eb 100644 (file)
--- 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;
 }