Mailing List Archive: [PATCH] gpio: null pointer dereference in error handling in gpiolib.c

Avoid calling desc_to_gpio() if desc->chip is NULL, as this will
cause a kernel panic.

In the code above the calls, there is a test for !chip, which
comes to the 'fail' label if true. In this case, the code
panics, since desc_to_gpio() uses desc->chip to look up the
gpio number.

An RFC patch that explained the cause of one example of panic when
desc->chip is NULL and fixed that example
(http://lkml.indiana.edu/hypermail/linux/kernel/1308.3/01473.html)
was accepted. This patch fixes the remaining locations which have
the same problem.

Signed-off-by: Frank Rowand <frank.rowand@sonymobile.com>

---
drivers/gpio/gpiolib.c | 33 24 + 9 - 0 !
1 file changed, 24 insertions(+), 9 deletions(-)

Index: b/drivers/gpio/gpiolib.c
===================================================================
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -1676,9 +1676,14 @@ lose:
return status;
fail:
spin_unlock_irqrestore(&gpio_lock, flags);
- if (status)
- pr_debug("%s: gpio-%d status %d\n", __func__,
- desc_to_gpio(desc), status);
+ if (status) {
+ if (desc->chip) {
+ pr_debug("%s: gpio-%d status %d\n", __func__,
+ desc_to_gpio(desc), status);
+ } else {
+ pr_debug("%s: gpio-?? status %d\n", __func__, status);
+ }
+ }
return status;
}

@@ -1745,9 +1750,14 @@ lose:
return status;
fail:
spin_unlock_irqrestore(&gpio_lock, flags);
- if (status)
- pr_debug("%s: gpio-%d status %d\n", __func__,
- desc_to_gpio(desc), status);
+ if (status) {
+ if (desc->chip) {
+ pr_debug("%s: gpio-%d status %d\n", __func__,
+ desc_to_gpio(desc), status);
+ } else {
+ pr_debug("%s: gpio-?? status %d\n", __func__, status);
+ }
+ }
return status;
}

@@ -1795,9 +1805,14 @@ static int gpiod_set_debounce(struct gpi

fail:
spin_unlock_irqrestore(&gpio_lock, flags);
- if (status)
- pr_debug("%s: gpio-%d status %d\n", __func__,
- desc_to_gpio(desc), status);
+ if (status) {
+ if (desc->chip) {
+ pr_debug("%s: gpio-%d status %d\n", __func__,
+ desc_to_gpio(desc), status);
+ } else {
+ pr_debug("%s: gpio-?? status %d\n", __func__, status);
+ }
+ }

return status;
}
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

On Fri, Aug 30, 2013 at 7:10 AM, Frank Rowand
<frank.rowand@sonymobile.com> wrote:

> Avoid calling desc_to_gpio() if desc->chip is NULL, as this will
> cause a kernel panic.
>
> In the code above the calls, there is a test for !chip, which
> comes to the 'fail' label if true. In this case, the code
> panics, since desc_to_gpio() uses desc->chip to look up the
> gpio number.
>
> An RFC patch that explained the cause of one example of panic when
> desc->chip is NULL and fixed that example
> (http://lkml.indiana.edu/hypermail/linux/kernel/1308.3/01473.html)
> was accepted. This patch fixes the remaining locations which have
> the same problem.
>
> Signed-off-by: Frank Rowand <frank.rowand@sonymobile.com>

Hm it appears Alexandre has another idea on how it should be
fixed, but he was in a hurry and didn't provide a proper patch.

Let me cook something up so we can see of we can get
this right.

Yours,
Linus Walleij
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/