From: Mukesh Ojha quic_mojha@quicinc.com
[ Upstream commit 5a3e85c3c397c781393ea5fb2f45b1f60f8a4e6e ]
When two client of the same gpio call pinctrl_select_state() for the same functionality, we are seeing NULL pointer issue while accessing desc->mux_owner.
Let's say two processes A, B executing in pin_request() for the same pin and process A updates the desc->mux_usecount but not yet updated the desc->mux_owner while process B see the desc->mux_usecount which got updated by A path and further executes strcmp and while accessing desc->mux_owner it crashes with NULL pointer.
Serialize the access to mux related setting with a mutex lock.
cpu0 (process A) cpu1(process B)
pinctrl_select_state() { pinctrl_select_state() { pin_request() { pin_request() { ... .... } else { desc->mux_usecount++; desc->mux_usecount && strcmp(desc->mux_owner, owner)) {
if (desc->mux_usecount > 1) return 0; desc->mux_owner = owner;
} }
Signed-off-by: Mukesh Ojha quic_mojha@quicinc.com Link: https://lore.kernel.org/20241014192930.1539673-1-quic_mojha@quicinc.com Signed-off-by: Linus Walleij linus.walleij@linaro.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/pinctrl/core.c | 3 + drivers/pinctrl/core.h | 1 + drivers/pinctrl/pinmux.c | 173 ++++++++++++++++++++++----------------- 3 files changed, 100 insertions(+), 77 deletions(-)
diff --git a/drivers/pinctrl/core.c b/drivers/pinctrl/core.c index 88ee086e13763..7342148c65729 100644 --- a/drivers/pinctrl/core.c +++ b/drivers/pinctrl/core.c @@ -220,6 +220,9 @@ static int pinctrl_register_one_pin(struct pinctrl_dev *pctldev,
/* Set owner */ pindesc->pctldev = pctldev; +#ifdef CONFIG_PINMUX + mutex_init(&pindesc->mux_lock); +#endif
/* Copy basic pin info */ if (pin->name) { diff --git a/drivers/pinctrl/core.h b/drivers/pinctrl/core.h index 530370443c191..ece4b9c71c970 100644 --- a/drivers/pinctrl/core.h +++ b/drivers/pinctrl/core.h @@ -177,6 +177,7 @@ struct pin_desc { const char *mux_owner; const struct pinctrl_setting_mux *mux_setting; const char *gpio_owner; + struct mutex mux_lock; #endif };
diff --git a/drivers/pinctrl/pinmux.c b/drivers/pinctrl/pinmux.c index 2a180a5d64a4a..97e8af88df851 100644 --- a/drivers/pinctrl/pinmux.c +++ b/drivers/pinctrl/pinmux.c @@ -13,6 +13,7 @@ #define pr_fmt(fmt) "pinmux core: " fmt
#include <linux/ctype.h> +#include <linux/cleanup.h> #include <linux/debugfs.h> #include <linux/device.h> #include <linux/err.h> @@ -93,6 +94,7 @@ bool pinmux_can_be_used_for_gpio(struct pinctrl_dev *pctldev, unsigned pin) if (!desc || !ops) return true;
+ guard(mutex)(&desc->mux_lock); if (ops->strict && desc->mux_usecount) return false;
@@ -127,29 +129,31 @@ static int pin_request(struct pinctrl_dev *pctldev, dev_dbg(pctldev->dev, "request pin %d (%s) for %s\n", pin, desc->name, owner);
- if ((!gpio_range || ops->strict) && - desc->mux_usecount && strcmp(desc->mux_owner, owner)) { - dev_err(pctldev->dev, - "pin %s already requested by %s; cannot claim for %s\n", - desc->name, desc->mux_owner, owner); - goto out; - } + scoped_guard(mutex, &desc->mux_lock) { + if ((!gpio_range || ops->strict) && + desc->mux_usecount && strcmp(desc->mux_owner, owner)) { + dev_err(pctldev->dev, + "pin %s already requested by %s; cannot claim for %s\n", + desc->name, desc->mux_owner, owner); + goto out; + }
- if ((gpio_range || ops->strict) && desc->gpio_owner) { - dev_err(pctldev->dev, - "pin %s already requested by %s; cannot claim for %s\n", - desc->name, desc->gpio_owner, owner); - goto out; - } + if ((gpio_range || ops->strict) && desc->gpio_owner) { + dev_err(pctldev->dev, + "pin %s already requested by %s; cannot claim for %s\n", + desc->name, desc->gpio_owner, owner); + goto out; + }
- if (gpio_range) { - desc->gpio_owner = owner; - } else { - desc->mux_usecount++; - if (desc->mux_usecount > 1) - return 0; + if (gpio_range) { + desc->gpio_owner = owner; + } else { + desc->mux_usecount++; + if (desc->mux_usecount > 1) + return 0;
- desc->mux_owner = owner; + desc->mux_owner = owner; + } }
/* Let each pin increase references to this module */ @@ -180,12 +184,14 @@ static int pin_request(struct pinctrl_dev *pctldev,
out_free_pin: if (status) { - if (gpio_range) { - desc->gpio_owner = NULL; - } else { - desc->mux_usecount--; - if (!desc->mux_usecount) - desc->mux_owner = NULL; + scoped_guard(mutex, &desc->mux_lock) { + if (gpio_range) { + desc->gpio_owner = NULL; + } else { + desc->mux_usecount--; + if (!desc->mux_usecount) + desc->mux_owner = NULL; + } } } out: @@ -221,15 +227,17 @@ static const char *pin_free(struct pinctrl_dev *pctldev, int pin, return NULL; }
- if (!gpio_range) { - /* - * A pin should not be freed more times than allocated. - */ - if (WARN_ON(!desc->mux_usecount)) - return NULL; - desc->mux_usecount--; - if (desc->mux_usecount) - return NULL; + scoped_guard(mutex, &desc->mux_lock) { + if (!gpio_range) { + /* + * A pin should not be freed more times than allocated. + */ + if (WARN_ON(!desc->mux_usecount)) + return NULL; + desc->mux_usecount--; + if (desc->mux_usecount) + return NULL; + } }
/* @@ -241,13 +249,15 @@ static const char *pin_free(struct pinctrl_dev *pctldev, int pin, else if (ops->free) ops->free(pctldev, pin);
- if (gpio_range) { - owner = desc->gpio_owner; - desc->gpio_owner = NULL; - } else { - owner = desc->mux_owner; - desc->mux_owner = NULL; - desc->mux_setting = NULL; + scoped_guard(mutex, &desc->mux_lock) { + if (gpio_range) { + owner = desc->gpio_owner; + desc->gpio_owner = NULL; + } else { + owner = desc->mux_owner; + desc->mux_owner = NULL; + desc->mux_setting = NULL; + } }
module_put(pctldev->owner); @@ -461,7 +471,8 @@ int pinmux_enable_setting(const struct pinctrl_setting *setting) pins[i]); continue; } - desc->mux_setting = &(setting->data.mux); + scoped_guard(mutex, &desc->mux_lock) + desc->mux_setting = &(setting->data.mux); }
ret = ops->set_mux(pctldev, setting->data.mux.func, @@ -475,8 +486,10 @@ int pinmux_enable_setting(const struct pinctrl_setting *setting) err_set_mux: for (i = 0; i < num_pins; i++) { desc = pin_desc_get(pctldev, pins[i]); - if (desc) - desc->mux_setting = NULL; + if (desc) { + scoped_guard(mutex, &desc->mux_lock) + desc->mux_setting = NULL; + } } err_pin_request: /* On error release all taken pins */ @@ -495,6 +508,7 @@ void pinmux_disable_setting(const struct pinctrl_setting *setting) unsigned num_pins = 0; int i; struct pin_desc *desc; + bool is_equal;
if (pctlops->get_group_pins) ret = pctlops->get_group_pins(pctldev, setting->data.mux.group, @@ -520,7 +534,10 @@ void pinmux_disable_setting(const struct pinctrl_setting *setting) pins[i]); continue; } - if (desc->mux_setting == &(setting->data.mux)) { + scoped_guard(mutex, &desc->mux_lock) + is_equal = (desc->mux_setting == &(setting->data.mux)); + + if (is_equal) { pin_free(pctldev, pins[i], NULL); } else { const char *gname; @@ -612,40 +629,42 @@ static int pinmux_pins_show(struct seq_file *s, void *what) if (desc == NULL) continue;
- if (desc->mux_owner && - !strcmp(desc->mux_owner, pinctrl_dev_get_name(pctldev))) - is_hog = true; - - if (pmxops->strict) { - if (desc->mux_owner) - seq_printf(s, "pin %d (%s): device %s%s", - pin, desc->name, desc->mux_owner, + scoped_guard(mutex, &desc->mux_lock) { + if (desc->mux_owner && + !strcmp(desc->mux_owner, pinctrl_dev_get_name(pctldev))) + is_hog = true; + + if (pmxops->strict) { + if (desc->mux_owner) + seq_printf(s, "pin %d (%s): device %s%s", + pin, desc->name, desc->mux_owner, + is_hog ? " (HOG)" : ""); + else if (desc->gpio_owner) + seq_printf(s, "pin %d (%s): GPIO %s", + pin, desc->name, desc->gpio_owner); + else + seq_printf(s, "pin %d (%s): UNCLAIMED", + pin, desc->name); + } else { + /* For non-strict controllers */ + seq_printf(s, "pin %d (%s): %s %s%s", pin, desc->name, + desc->mux_owner ? desc->mux_owner + : "(MUX UNCLAIMED)", + desc->gpio_owner ? desc->gpio_owner + : "(GPIO UNCLAIMED)", is_hog ? " (HOG)" : ""); - else if (desc->gpio_owner) - seq_printf(s, "pin %d (%s): GPIO %s", - pin, desc->name, desc->gpio_owner); + } + + /* If mux: print function+group claiming the pin */ + if (desc->mux_setting) + seq_printf(s, " function %s group %s\n", + pmxops->get_function_name(pctldev, + desc->mux_setting->func), + pctlops->get_group_name(pctldev, + desc->mux_setting->group)); else - seq_printf(s, "pin %d (%s): UNCLAIMED", - pin, desc->name); - } else { - /* For non-strict controllers */ - seq_printf(s, "pin %d (%s): %s %s%s", pin, desc->name, - desc->mux_owner ? desc->mux_owner - : "(MUX UNCLAIMED)", - desc->gpio_owner ? desc->gpio_owner - : "(GPIO UNCLAIMED)", - is_hog ? " (HOG)" : ""); + seq_putc(s, '\n'); } - - /* If mux: print function+group claiming the pin */ - if (desc->mux_setting) - seq_printf(s, " function %s group %s\n", - pmxops->get_function_name(pctldev, - desc->mux_setting->func), - pctlops->get_group_name(pctldev, - desc->mux_setting->group)); - else - seq_putc(s, '\n'); }
mutex_unlock(&pctldev->mutex);