Commit 805f7aaf authored by Rob Herring (Arm)'s avatar Rob Herring (Arm) Committed by Lee Jones
Browse files

mfd: syscon: Fix race in device_node_get_regmap() 



It is possible for multiple, simultaneous callers calling
device_node_get_regmap() with the same node to fail to find an entry in
the syscon_list. There is a period of time while the first caller is
calling of_syscon_register() that subsequent callers also fail to find
an entry in the syscon_list and then call of_syscon_register() a second
time.

Fix this by keeping the lock held until after of_syscon_register()
completes and adds the node to syscon_list. Convert the spinlock to a
mutex as many of the functions called in of_syscon_register() such as
kzalloc() and of_clk_get() may sleep.

Fixes: bdb0066d ("mfd: syscon: Decouple syscon interface from platform devices")
Signed-off-by: default avatarRob Herring (Arm) <robh@kernel.org>
Reviewed-by: default avatarKrzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Tested-by: default avatarKrzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Tested-by: default avatarWill McVicker <willmcvicker@google.com>
Tested-by: default avatarPankaj Dubey <pankaj.dubey@samsung.com>
Reviewed-by: default avatarPankaj Dubey <pankaj.dubey@samsung.com>
Link: https://lore.kernel.org/r/20241217-syscon-fixes-v2-1-4f56d750541d@kernel.org


Signed-off-by: default avatarLee Jones <lee@kernel.org>
parent b55689c0

drivers/mfd/syscon.c

+10 −9
Original line number Diff line number Diff line
@@ -15,6 +15,7 @@ 
#include <linux/io.h>

#include <linux/init.h>

#include <linux/list.h>

#include <linux/mutex.h>

#include <linux/of.h>

#include <linux/of_address.h>

#include <linux/of_platform.h>
@@ -27,7 +28,7 @@ 


static struct platform_driver syscon_driver;



static DEFINE_SPINLOCK(syscon_list_slock);

static DEFINE_MUTEX(syscon_list_lock);

static LIST_HEAD(syscon_list);



struct syscon {
@@ -54,6 +55,8 @@ static struct syscon *of_syscon_register(struct device_node *np, bool check_res) 
	struct resource res;

	struct reset_control *reset;



	WARN_ON(!mutex_is_locked(&syscon_list_lock));



	struct syscon *syscon __free(kfree) = kzalloc(sizeof(*syscon), GFP_KERNEL);

	if (!syscon)

		return ERR_PTR(-ENOMEM);
@@ -146,9 +149,7 @@ static struct syscon *of_syscon_register(struct device_node *np, bool check_res) 
	syscon->regmap = regmap;

	syscon->np = np;



	spin_lock(&syscon_list_slock);

	list_add_tail(&syscon->list, &syscon_list);

	spin_unlock(&syscon_list_slock);



	return_ptr(syscon);
@@ -169,7 +170,7 @@ static struct regmap *device_node_get_regmap(struct device_node *np, 
{

	struct syscon *entry, *syscon = NULL;



	spin_lock(&syscon_list_slock);

	mutex_lock(&syscon_list_lock);



	list_for_each_entry(entry, &syscon_list, list)

		if (entry->np == np) {
@@ -177,11 +178,11 @@ static struct regmap *device_node_get_regmap(struct device_node *np, 
			break;

		}



	spin_unlock(&syscon_list_slock);



	if (!syscon)

		syscon = of_syscon_register(np, check_res);



	mutex_unlock(&syscon_list_lock);



	if (IS_ERR(syscon))

		return ERR_CAST(syscon);
@@ -212,7 +213,7 @@ int of_syscon_register_regmap(struct device_node *np, struct regmap *regmap) 
		return -ENOMEM;



	/* check if syscon entry already exists */

	spin_lock(&syscon_list_slock);

	mutex_lock(&syscon_list_lock);



	list_for_each_entry(entry, &syscon_list, list)

		if (entry->np == np) {
@@ -225,12 +226,12 @@ int of_syscon_register_regmap(struct device_node *np, struct regmap *regmap) 


	/* register the regmap in syscon list */

	list_add_tail(&syscon->list, &syscon_list);

	spin_unlock(&syscon_list_slock);

	mutex_unlock(&syscon_list_lock);



	return 0;



err_unlock:

	spin_unlock(&syscon_list_slock);

	mutex_unlock(&syscon_list_lock);

	kfree(syscon);

	return ret;

}