From: Muchun Song <smuchun@gmail.com>
To: linus.walleij@linaro.org, bgolaszewski@baylibre.com
Cc: linux-gpio@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH v2] gpiolib: Fix possible use after free on label
Date: Thu, 1 Nov 2018 21:12:50 +0800 [thread overview]
Message-ID: <20181101131250.41636-1-smuchun@gmail.com> (raw)
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>
---
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 25187403e3ac..550918268549 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -2270,6 +2270,12 @@ 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,
@@ -2280,6 +2286,7 @@ 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;
}
@@ -2296,6 +2303,7 @@ 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;
}
@@ -2391,6 +2399,7 @@ 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);
@@ -3212,11 +3221,19 @@ 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 21ddbe440030..acc4279ad5e3 100644
--- a/include/linux/gpio/consumer.h
+++ b/include/linux/gpio/consumer.h
@@ -142,7 +142,7 @@ 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);
@@ -465,10 +465,12 @@ 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)
--
2.17.1
next reply other threads:[~2018-11-01 13:13 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-01 13:12 Muchun Song [this message]
2018-11-01 15:27 ` [PATCH v2] gpiolib: Fix possible use after free on label Linus Walleij
2018-11-02 9:24 ` Linus Walleij
2018-11-02 16:12 ` Nicolas Pitre
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20181101131250.41636-1-smuchun@gmail.com \
--to=smuchun@gmail.com \
--cc=bgolaszewski@baylibre.com \
--cc=linus.walleij@linaro.org \
--cc=linux-gpio@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).