4.20-stable review patch. If anyone has any objections, please let me know.
------------------
[ Upstream commit 18534df419041e6c1f4b41af56ee7d41f757815c ]
gpiod_request_commit() copies the pointer to the label passed as an argument only to be used later. But there's a chance the caller could immediately free the passed string(e.g., local variable). This could trigger a use after free when we use gpio label(e.g., gpiochip_unlock_as_irq(), gpiochip_is_requested()).
To be on the safe side: duplicate the string with kstrdup_const() so that if an unaware user passes an address to a stack-allocated buffer, we won't get the arbitrary label.
Also fix gpiod_set_consumer_name().
Signed-off-by: Muchun Song smuchun@gmail.com Signed-off-by: Linus Walleij linus.walleij@linaro.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/gpio/gpiolib.c | 25 +++++++++++++++++++++---- include/linux/gpio/consumer.h | 6 ++++-- 2 files changed, 25 insertions(+), 6 deletions(-)
diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c index 76913e23cf3a..bd44be115cdd 100644 --- a/drivers/gpio/gpiolib.c +++ b/drivers/gpio/gpiolib.c @@ -2306,6 +2306,12 @@ static int gpiod_request_commit(struct gpio_desc *desc, const char *label) unsigned long flags; unsigned offset;
+ if (label) { + label = kstrdup_const(label, GFP_KERNEL); + if (!label) + return -ENOMEM; + } + spin_lock_irqsave(&gpio_lock, flags);
/* NOTE: gpio_request() can be called in early boot, @@ -2316,6 +2322,7 @@ static int gpiod_request_commit(struct gpio_desc *desc, const char *label) desc_set_label(desc, label ? : "?"); status = 0; } else { + kfree_const(label); status = -EBUSY; goto done; } @@ -2332,6 +2339,7 @@ static int gpiod_request_commit(struct gpio_desc *desc, const char *label)
if (status < 0) { desc_set_label(desc, NULL); + kfree_const(label); clear_bit(FLAG_REQUESTED, &desc->flags); goto done; } @@ -2427,6 +2435,7 @@ static bool gpiod_free_commit(struct gpio_desc *desc) chip->free(chip, gpio_chip_hwgpio(desc)); spin_lock_irqsave(&gpio_lock, flags); } + kfree_const(desc->label); desc_set_label(desc, NULL); clear_bit(FLAG_ACTIVE_LOW, &desc->flags); clear_bit(FLAG_REQUESTED, &desc->flags); @@ -3382,11 +3391,19 @@ EXPORT_SYMBOL_GPL(gpiod_cansleep); * @desc: gpio to set the consumer name on * @name: the new consumer name */ -void gpiod_set_consumer_name(struct gpio_desc *desc, const char *name) +int gpiod_set_consumer_name(struct gpio_desc *desc, const char *name) { - VALIDATE_DESC_VOID(desc); - /* Just overwrite whatever the previous name was */ - desc->label = name; + VALIDATE_DESC(desc); + if (name) { + name = kstrdup_const(name, GFP_KERNEL); + if (!name) + return -ENOMEM; + } + + kfree_const(desc->label); + desc_set_label(desc, name); + + return 0; } EXPORT_SYMBOL_GPL(gpiod_set_consumer_name);
diff --git a/include/linux/gpio/consumer.h b/include/linux/gpio/consumer.h index f2f887795d43..ed070512b40e 100644 --- a/include/linux/gpio/consumer.h +++ b/include/linux/gpio/consumer.h @@ -162,7 +162,7 @@ int gpiod_is_active_low(const struct gpio_desc *desc); int gpiod_cansleep(const struct gpio_desc *desc);
int gpiod_to_irq(const struct gpio_desc *desc); -void gpiod_set_consumer_name(struct gpio_desc *desc, const char *name); +int gpiod_set_consumer_name(struct gpio_desc *desc, const char *name);
/* Convert between the old gpio_ and new gpiod_ interfaces */ struct gpio_desc *gpio_to_desc(unsigned gpio); @@ -495,10 +495,12 @@ static inline int gpiod_to_irq(const struct gpio_desc *desc) return -EINVAL; }
-static inline void gpiod_set_consumer_name(struct gpio_desc *desc, const char *name) +static inline int gpiod_set_consumer_name(struct gpio_desc *desc, + const char *name) { /* GPIO can never have been requested */ WARN_ON(1); + return -EINVAL; }
static inline struct gpio_desc *gpio_to_desc(unsigned gpio)