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[3.19.y-ckt,stable] Patch "regmap: Fix possible shift overflow in regmap_field_init()" has been added to staging queue

Message ID 1437008456-2356-1-git-send-email-kamal@canonical.com
State New
Headers show

Commit Message

Kamal Mostafa July 16, 2015, 1 a.m. UTC
This is a note to let you know that I have just added a patch titled

    regmap: Fix possible shift overflow in regmap_field_init()

to the linux-3.19.y-queue branch of the 3.19.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.19.y-queue

This patch is scheduled to be released in version 3.19.y-ckt4.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.19.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

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From 720950666a92030e9fb5dd75a249c5f448ba19d7 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()

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: Kamal Mostafa <kamal@canonical.com>
---
 drivers/base/regmap/regmap.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

--
1.9.1
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Patch

diff --git a/drivers/base/regmap/regmap.c b/drivers/base/regmap/regmap.c
index a434df6..b389c1d 100644
--- a/drivers/base/regmap/regmap.c
+++ b/drivers/base/regmap/regmap.c
@@ -944,11 +944,10 @@  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;
 }