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mfd: syscon: Fix race in device_node_get_regmap()

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[ Upstream commit 805f7aaf7fee14a57b56af01d270edf6c10765e8 ]

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: bdb0066df9 ("mfd: syscon: Decouple syscon interface from platform devices")
Signed-off-by: Rob Herring (Arm) <robh@kernel.org>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Tested-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Tested-by: Will McVicker <willmcvicker@google.com>
Tested-by: Pankaj Dubey <pankaj.dubey@samsung.com>
Reviewed-by: Pankaj Dubey <pankaj.dubey@samsung.com>
Link: https://lore.kernel.org/r/20241217-syscon-fixes-v2-1-4f56d750541d@kernel.org
Signed-off-by: Lee Jones <lee@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Rob Herring (Arm) 2024-12-17 12:11:40 -06:00 committed by Greg Kroah-Hartman
parent 5481df0e05
commit fa78395d95
1 changed files with 10 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

19
drivers/mfd/syscon.c
View File

@ -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>
@ -26,7 +27,7 @@
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 {
@ -51,6 +52,8 @@ static struct syscon *of_syscon_register(struct device_node *np, bool check_clk)
struct regmap_config syscon_config = syscon_regmap_config;
struct resource res;
WARN_ON(!mutex_is_locked(&syscon_list_lock));
struct syscon *syscon __free(kfree) = kzalloc(sizeof(*syscon), GFP_KERNEL);
if (!syscon)
return ERR_PTR(-ENOMEM);
@ -131,9 +134,7 @@ static struct syscon *of_syscon_register(struct device_node *np, bool check_clk)
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);
@ -152,7 +153,7 @@ 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) {
@ -160,11 +161,11 @@ 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_clk);
mutex_unlock(&syscon_list_lock);
if (IS_ERR(syscon))
return ERR_CAST(syscon);
@ -195,7 +196,7 @@ 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) {
@ -208,12 +209,12 @@ 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;
}