[PATCH 1/3] mfd: syscon: Fix race in device_node_get_regmap()
From: "Rob Herring (Arm)" <robh@kernel.org>
Date: 2024-12-11 20:57:30
Also in:
lkml
Subsystem:
multifunction devices (mfd), system configuration (syscon), the rest · Maintainers:
Lee Jones, Arnd Bergmann, Linus Torvalds
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() may sleep.
Fixes: bdb0066df96e ("mfd: syscon: Decouple syscon interface from platform devices")
Signed-off-by: Rob Herring (Arm) <robh@kernel.org>
---
drivers/mfd/syscon.c | 19 ++++++++++---------
1 file changed, 10 insertions(+), 9 deletions(-)
diff --git a/drivers/mfd/syscon.c b/drivers/mfd/syscon.c
index 3e1d699ba934..72f20de9652d 100644
--- a/drivers/mfd/syscon.c
+++ b/drivers/mfd/syscon.c@@ -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; }
--
2.45.2