From: Bartosz Golaszewski <[email protected]>
We must not call pinctrl_gpio_can_use_line() with the gpio_lock taken
as it takes a mutex internally. Let's move the call before taking the
spinlock and store the return value.
This isn't perfect - there's a moment between calling
pinctrl_gpio_can_use_line() and taking the spinlock where the situation
can change but it isn't a regression either: previously this part wasn't
protected at all and it only affects the information user-space is
seeing.
Reported-by: Geert Uytterhoeven <[email protected]>
Fixes: d2ac25798208 ("gpiolib: provide a dedicated function for setting lineinfo")
Signed-off-by: Bartosz Golaszewski <[email protected]>
---
drivers/gpio/gpiolib.c | 13 ++++++++++++-
1 file changed, 12 insertions(+), 1 deletion(-)
diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 02f8b2b81199..ee20634a522c 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -1154,8 +1154,19 @@ static void gpio_desc_to_lineinfo(struct gpio_desc *desc,
struct gpioline_info *info)
{
struct gpio_chip *chip = desc->gdev->chip;
+ bool ok_for_pinctrl;
unsigned long flags;
+ /*
+ * This function takes a mutex so we must check this before taking
+ * the spinlock.
+ *
+ * FIXME: find a non-racy way to retrieve this information. Maybe a
+ * lock common to both frameworks?
+ */
+ ok_for_pinctrl = pinctrl_gpio_can_use_line(
+ chip->base + info->line_offset);
+
spin_lock_irqsave(&gpio_lock, flags);
if (desc->name) {
@@ -1182,7 +1193,7 @@ static void gpio_desc_to_lineinfo(struct gpio_desc *desc,
test_bit(FLAG_USED_AS_IRQ, &desc->flags) ||
test_bit(FLAG_EXPORT, &desc->flags) ||
test_bit(FLAG_SYSFS, &desc->flags) ||
- !pinctrl_gpio_can_use_line(chip->base + info->line_offset))
+ !ok_for_pinctrl)
info->flags |= GPIOLINE_FLAG_KERNEL;
if (test_bit(FLAG_IS_OUT, &desc->flags))
info->flags |= GPIOLINE_FLAG_IS_OUT;
--
2.25.0
Hi Bartosz,
On Fri, Mar 20, 2020 at 10:31 AM Bartosz Golaszewski <[email protected]> wrote:
> From: Bartosz Golaszewski <[email protected]>
>
> We must not call pinctrl_gpio_can_use_line() with the gpio_lock taken
> as it takes a mutex internally. Let's move the call before taking the
> spinlock and store the return value.
>
> This isn't perfect - there's a moment between calling
> pinctrl_gpio_can_use_line() and taking the spinlock where the situation
> can change but it isn't a regression either: previously this part wasn't
> protected at all and it only affects the information user-space is
> seeing.
>
> Reported-by: Geert Uytterhoeven <[email protected]>
> Fixes: d2ac25798208 ("gpiolib: provide a dedicated function for setting lineinfo")
> Signed-off-by: Bartosz Golaszewski <[email protected]>
Thanks for your patch!
> --- a/drivers/gpio/gpiolib.c
> +++ b/drivers/gpio/gpiolib.c
> @@ -1154,8 +1154,19 @@ static void gpio_desc_to_lineinfo(struct gpio_desc *desc,
> struct gpioline_info *info)
> {
> struct gpio_chip *chip = desc->gdev->chip;
> + bool ok_for_pinctrl;
> unsigned long flags;
>
> + /*
> + * This function takes a mutex so we must check this before taking
> + * the spinlock.
> + *
> + * FIXME: find a non-racy way to retrieve this information. Maybe a
> + * lock common to both frameworks?
> + */
> + ok_for_pinctrl = pinctrl_gpio_can_use_line(
> + chip->base + info->line_offset);
Note that this is now called unconditionally, while before it was only called
if all previous steps in the ||-pipeline failed.
> +
> spin_lock_irqsave(&gpio_lock, flags);
>
> if (desc->name) {
> @@ -1182,7 +1193,7 @@ static void gpio_desc_to_lineinfo(struct gpio_desc *desc,
> test_bit(FLAG_USED_AS_IRQ, &desc->flags) ||
> test_bit(FLAG_EXPORT, &desc->flags) ||
> test_bit(FLAG_SYSFS, &desc->flags) ||
> - !pinctrl_gpio_can_use_line(chip->base + info->line_offset))
> + !ok_for_pinctrl)
> info->flags |= GPIOLINE_FLAG_KERNEL;
> if (test_bit(FLAG_IS_OUT, &desc->flags))
> info->flags |= GPIOLINE_FLAG_IS_OUT;
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- [email protected]
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
pt., 20 mar 2020 o 11:59 Geert Uytterhoeven <[email protected]> napisał(a):
>
> Hi Bartosz,
>
> On Fri, Mar 20, 2020 at 10:31 AM Bartosz Golaszewski <[email protected]> wrote:
> > From: Bartosz Golaszewski <[email protected]>
> >
> > We must not call pinctrl_gpio_can_use_line() with the gpio_lock taken
> > as it takes a mutex internally. Let's move the call before taking the
> > spinlock and store the return value.
> >
> > This isn't perfect - there's a moment between calling
> > pinctrl_gpio_can_use_line() and taking the spinlock where the situation
> > can change but it isn't a regression either: previously this part wasn't
> > protected at all and it only affects the information user-space is
> > seeing.
> >
> > Reported-by: Geert Uytterhoeven <[email protected]>
> > Fixes: d2ac25798208 ("gpiolib: provide a dedicated function for setting lineinfo")
> > Signed-off-by: Bartosz Golaszewski <[email protected]>
>
> Thanks for your patch!
>
> > --- a/drivers/gpio/gpiolib.c
> > +++ b/drivers/gpio/gpiolib.c
> > @@ -1154,8 +1154,19 @@ static void gpio_desc_to_lineinfo(struct gpio_desc *desc,
> > struct gpioline_info *info)
> > {
> > struct gpio_chip *chip = desc->gdev->chip;
> > + bool ok_for_pinctrl;
> > unsigned long flags;
> >
> > + /*
> > + * This function takes a mutex so we must check this before taking
> > + * the spinlock.
> > + *
> > + * FIXME: find a non-racy way to retrieve this information. Maybe a
> > + * lock common to both frameworks?
> > + */
> > + ok_for_pinctrl = pinctrl_gpio_can_use_line(
> > + chip->base + info->line_offset);
>
> Note that this is now called unconditionally, while before it was only called
> if all previous steps in the ||-pipeline failed.
>
Is this a problem though? Doesn't seem so. Am I missing something?
Bart
On Fri, Mar 20, 2020 at 10:31 AM Bartosz Golaszewski <[email protected]> wrote:
> From: Bartosz Golaszewski <[email protected]>
>
> We must not call pinctrl_gpio_can_use_line() with the gpio_lock taken
> as it takes a mutex internally. Let's move the call before taking the
> spinlock and store the return value.
>
> This isn't perfect - there's a moment between calling
> pinctrl_gpio_can_use_line() and taking the spinlock where the situation
> can change but it isn't a regression either: previously this part wasn't
> protected at all and it only affects the information user-space is
> seeing.
>
> Reported-by: Geert Uytterhoeven <[email protected]>
> Fixes: d2ac25798208 ("gpiolib: provide a dedicated function for setting lineinfo")
> Signed-off-by: Bartosz Golaszewski <[email protected]>
I'm sorry that I lost track of this patch :(
Do we still need something like this or has it been fixed
by some other patches?
Yours,
Linus Walleij
wt., 14 kwi 2020 o 14:00 Linus Walleij <[email protected]> napisał(a):
>
> On Fri, Mar 20, 2020 at 10:31 AM Bartosz Golaszewski <[email protected]> wrote:
>
> > From: Bartosz Golaszewski <[email protected]>
> >
> > We must not call pinctrl_gpio_can_use_line() with the gpio_lock taken
> > as it takes a mutex internally. Let's move the call before taking the
> > spinlock and store the return value.
> >
> > This isn't perfect - there's a moment between calling
> > pinctrl_gpio_can_use_line() and taking the spinlock where the situation
> > can change but it isn't a regression either: previously this part wasn't
> > protected at all and it only affects the information user-space is
> > seeing.
> >
> > Reported-by: Geert Uytterhoeven <[email protected]>
> > Fixes: d2ac25798208 ("gpiolib: provide a dedicated function for setting lineinfo")
> > Signed-off-by: Bartosz Golaszewski <[email protected]>
>
> I'm sorry that I lost track of this patch :(
>
> Do we still need something like this or has it been fixed
> by some other patches?
>
> Yours,
> Linus Walleij
Nope, this is still an issue. Do you have a better idea than mine?
Bart
On Tue, Apr 14, 2020 at 2:27 PM Bartosz Golaszewski
<[email protected]> wrote:
> wt., 14 kwi 2020 o 14:00 Linus Walleij <[email protected]> napisał(a):
> >
> > On Fri, Mar 20, 2020 at 10:31 AM Bartosz Golaszewski <[email protected]> wrote:
> >
> > > From: Bartosz Golaszewski <[email protected]>
> > >
> > > We must not call pinctrl_gpio_can_use_line() with the gpio_lock taken
> > > as it takes a mutex internally. Let's move the call before taking the
> > > spinlock and store the return value.
> > >
> > > This isn't perfect - there's a moment between calling
> > > pinctrl_gpio_can_use_line() and taking the spinlock where the situation
> > > can change but it isn't a regression either: previously this part wasn't
> > > protected at all and it only affects the information user-space is
> > > seeing.
> > >
> > > Reported-by: Geert Uytterhoeven <[email protected]>
> > > Fixes: d2ac25798208 ("gpiolib: provide a dedicated function for setting lineinfo")
> > > Signed-off-by: Bartosz Golaszewski <[email protected]>
> >
> > I'm sorry that I lost track of this patch :(
> >
> > Do we still need something like this or has it been fixed
> > by some other patches?
> >
> > Yours,
> > Linus Walleij
>
> Nope, this is still an issue. Do you have a better idea than mine?
Nope, can you just queue it in your tree?
Acked-by: Linus Walleij <[email protected]>
Yours,
Linus Walleij
On Tue, Apr 14, 2020 at 6:35 PM Bartosz Golaszewski
<[email protected]> wrote:
>
> wt., 14 kwi 2020 o 14:00 Linus Walleij <[email protected]> napisał(a):
> >
> > On Fri, Mar 20, 2020 at 10:31 AM Bartosz Golaszewski <[email protected]> wrote:
> >
> > > From: Bartosz Golaszewski <[email protected]>
> > >
> > > We must not call pinctrl_gpio_can_use_line() with the gpio_lock taken
> > > as it takes a mutex internally. Let's move the call before taking the
> > > spinlock and store the return value.
> > >
> > > This isn't perfect - there's a moment between calling
> > > pinctrl_gpio_can_use_line() and taking the spinlock where the situation
> > > can change but it isn't a regression either: previously this part wasn't
> > > protected at all and it only affects the information user-space is
> > > seeing.
It seems I have no original at hand, so, commenting here.
It looks like we need a mutex less function which can be used here and
in the call you are considering racy.
Note, mutex followed by spin lock is fine, other way around is not.
So, here you should have something like
mutex_lock
ok_for_gpio = ...
spin_lock
...
spin_unlock
mutex_unlock.
--
With Best Regards,
Andy Shevchenko
wt., 28 kwi 2020 o 17:53 Andy Shevchenko <[email protected]> napisał(a):
>
> On Tue, Apr 14, 2020 at 6:35 PM Bartosz Golaszewski
> <[email protected]> wrote:
> >
> > wt., 14 kwi 2020 o 14:00 Linus Walleij <[email protected]> napisał(a):
> > >
> > > On Fri, Mar 20, 2020 at 10:31 AM Bartosz Golaszewski <[email protected]> wrote:
> > >
> > > > From: Bartosz Golaszewski <[email protected]>
> > > >
> > > > We must not call pinctrl_gpio_can_use_line() with the gpio_lock taken
> > > > as it takes a mutex internally. Let's move the call before taking the
> > > > spinlock and store the return value.
> > > >
> > > > This isn't perfect - there's a moment between calling
> > > > pinctrl_gpio_can_use_line() and taking the spinlock where the situation
> > > > can change but it isn't a regression either: previously this part wasn't
> > > > protected at all and it only affects the information user-space is
> > > > seeing.
>
> It seems I have no original at hand, so, commenting here.
>
> It looks like we need a mutex less function which can be used here and
> in the call you are considering racy.
The thing is this mutex is in pinctrl - we'd need to export it too so
that gpio can use it.
Bart
On Wed, Apr 29, 2020 at 9:40 AM Bartosz Golaszewski
<[email protected]> wrote:
> wt., 28 kwi 2020 o 17:53 Andy Shevchenko <[email protected]> napisał(a):
> > On Tue, Apr 14, 2020 at 6:35 PM Bartosz Golaszewski
> > <[email protected]> wrote:
> > > wt., 14 kwi 2020 o 14:00 Linus Walleij <[email protected]> napisał(a):
> > > > On Fri, Mar 20, 2020 at 10:31 AM Bartosz Golaszewski <[email protected]> wrote:
...
> > It looks like we need a mutex less function which can be used here and
> > in the call you are considering racy.
>
> The thing is this mutex is in pinctrl - we'd need to export it too so
> that gpio can use it.
Oh, I see now. So, something like
pinctrl_ext_operation_begin()
....
pinctrl_ext_operation_end()
perhaps.
--
With Best Regards,
Andy Shevchenko