2023-06-28 08:30:00

by Chengfeng Ye

[permalink] [raw]
Subject: [PATCH] mfd: qcom-pm8xxx: Fix potential deadlock on &chip->pm_irq_lock

As &chip->pm_irq_lock is acquired by pm8xxx_irq_handler() under irq
context, other process context code should disable irq before acquiring
the lock.

I think .irq_set_type and .irq_get_irqchip_state callbacks should be
executed from process context without irq disabled by default. Thus the
same lock acquision should disable irq.

Possible deadlock scenario
pm8xxx_irq_set_type()
-> pm8xxx_config_irq()
-> spin_lock(&chip->pm_irq_lock)
<irq interrupt>
-> pm8xxx_irq_handler()
-> pm8xxx_irq_master_handler()
-> pm8xxx_irq_block_handler()
-> pm8xxx_read_block_irq()
-> spin_lock(&chip->pm_irq_lock) (deadlock here)

This flaw was found using an experimental static analysis tool we are
developing for irq-related deadlock.

The tentative patch fix the potential deadlock by spin_lock_irqsave().

Signed-off-by: Chengfeng Ye <[email protected]>
---
drivers/mfd/qcom-pm8xxx.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/drivers/mfd/qcom-pm8xxx.c b/drivers/mfd/qcom-pm8xxx.c
index 9a948df8c28d..07c531bd1236 100644
--- a/drivers/mfd/qcom-pm8xxx.c
+++ b/drivers/mfd/qcom-pm8xxx.c
@@ -103,8 +103,9 @@ static int
pm8xxx_config_irq(struct pm_irq_chip *chip, unsigned int bp, unsigned int cp)
{
int rc;
+ unsigned long flags;

- spin_lock(&chip->pm_irq_lock);
+ spin_lock_irqsave(&chip->pm_irq_lock, flags);
rc = regmap_write(chip->regmap, SSBI_REG_ADDR_IRQ_BLK_SEL, bp);
if (rc) {
pr_err("Failed Selecting Block %d rc=%d\n", bp, rc);
@@ -116,7 +117,7 @@ pm8xxx_config_irq(struct pm_irq_chip *chip, unsigned int bp, unsigned int cp)
if (rc)
pr_err("Failed Configuring IRQ rc=%d\n", rc);
bail:
- spin_unlock(&chip->pm_irq_lock);
+ spin_unlock_irqrestore(&chip->pm_irq_lock, flags);
return rc;
}

@@ -321,6 +322,7 @@ static int pm8xxx_irq_get_irqchip_state(struct irq_data *d,
struct pm_irq_chip *chip = irq_data_get_irq_chip_data(d);
unsigned int pmirq = irqd_to_hwirq(d);
unsigned int bits;
+ unsigned long flags;
int irq_bit;
u8 block;
int rc;
@@ -331,7 +333,7 @@ static int pm8xxx_irq_get_irqchip_state(struct irq_data *d,
block = pmirq / 8;
irq_bit = pmirq % 8;

- spin_lock(&chip->pm_irq_lock);
+ spin_lock_irqsave(&chip->pm_irq_lock, flags);
rc = regmap_write(chip->regmap, SSBI_REG_ADDR_IRQ_BLK_SEL, block);
if (rc) {
pr_err("Failed Selecting Block %d rc=%d\n", block, rc);
@@ -346,7 +348,7 @@ static int pm8xxx_irq_get_irqchip_state(struct irq_data *d,

*state = !!(bits & BIT(irq_bit));
bail:
- spin_unlock(&chip->pm_irq_lock);
+ spin_unlock_irqrestore(&chip->pm_irq_lock, flags);

return rc;
}
--
2.17.1



2023-07-13 10:50:07

by Lee Jones

[permalink] [raw]
Subject: Re: [PATCH] mfd: qcom-pm8xxx: Fix potential deadlock on &chip->pm_irq_lock

I'd like some additional eyes-on please.

This is very old code that you're changing and some of the people who
made the largest contributions are not on Cc.

On Wed, 28 Jun 2023, Chengfeng Ye wrote:
> As &chip->pm_irq_lock is acquired by pm8xxx_irq_handler() under irq
> context, other process context code should disable irq before acquiring
> the lock.
>
> I think .irq_set_type and .irq_get_irqchip_state callbacks should be
> executed from process context without irq disabled by default. Thus the
> same lock acquision should disable irq.
>
> Possible deadlock scenario
> pm8xxx_irq_set_type()
> -> pm8xxx_config_irq()
> -> spin_lock(&chip->pm_irq_lock)
> <irq interrupt>
> -> pm8xxx_irq_handler()
> -> pm8xxx_irq_master_handler()
> -> pm8xxx_irq_block_handler()
> -> pm8xxx_read_block_irq()
> -> spin_lock(&chip->pm_irq_lock) (deadlock here)
>
> This flaw was found using an experimental static analysis tool we are
> developing for irq-related deadlock.
>
> The tentative patch fix the potential deadlock by spin_lock_irqsave().
>
> Signed-off-by: Chengfeng Ye <[email protected]>
> ---
> drivers/mfd/qcom-pm8xxx.c | 10 ++++++----
> 1 file changed, 6 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/mfd/qcom-pm8xxx.c b/drivers/mfd/qcom-pm8xxx.c
> index 9a948df8c28d..07c531bd1236 100644
> --- a/drivers/mfd/qcom-pm8xxx.c
> +++ b/drivers/mfd/qcom-pm8xxx.c
> @@ -103,8 +103,9 @@ static int
> pm8xxx_config_irq(struct pm_irq_chip *chip, unsigned int bp, unsigned int cp)
> {
> int rc;
> + unsigned long flags;
>
> - spin_lock(&chip->pm_irq_lock);
> + spin_lock_irqsave(&chip->pm_irq_lock, flags);
> rc = regmap_write(chip->regmap, SSBI_REG_ADDR_IRQ_BLK_SEL, bp);
> if (rc) {
> pr_err("Failed Selecting Block %d rc=%d\n", bp, rc);
> @@ -116,7 +117,7 @@ pm8xxx_config_irq(struct pm_irq_chip *chip, unsigned int bp, unsigned int cp)
> if (rc)
> pr_err("Failed Configuring IRQ rc=%d\n", rc);
> bail:
> - spin_unlock(&chip->pm_irq_lock);
> + spin_unlock_irqrestore(&chip->pm_irq_lock, flags);
> return rc;
> }
>
> @@ -321,6 +322,7 @@ static int pm8xxx_irq_get_irqchip_state(struct irq_data *d,
> struct pm_irq_chip *chip = irq_data_get_irq_chip_data(d);
> unsigned int pmirq = irqd_to_hwirq(d);
> unsigned int bits;
> + unsigned long flags;
> int irq_bit;
> u8 block;
> int rc;
> @@ -331,7 +333,7 @@ static int pm8xxx_irq_get_irqchip_state(struct irq_data *d,
> block = pmirq / 8;
> irq_bit = pmirq % 8;
>
> - spin_lock(&chip->pm_irq_lock);
> + spin_lock_irqsave(&chip->pm_irq_lock, flags);
> rc = regmap_write(chip->regmap, SSBI_REG_ADDR_IRQ_BLK_SEL, block);
> if (rc) {
> pr_err("Failed Selecting Block %d rc=%d\n", block, rc);
> @@ -346,7 +348,7 @@ static int pm8xxx_irq_get_irqchip_state(struct irq_data *d,
>
> *state = !!(bits & BIT(irq_bit));
> bail:
> - spin_unlock(&chip->pm_irq_lock);
> + spin_unlock_irqrestore(&chip->pm_irq_lock, flags);
>
> return rc;
> }
> --
> 2.17.1
>

--
Lee Jones [李琼斯]

2023-07-18 07:58:59

by Chengfeng Ye

[permalink] [raw]
Subject: Re: [PATCH] mfd: qcom-pm8xxx: Fix potential deadlock on &chip->pm_irq_lock

> This is very old code that you're changing and some of the people who
> made the largest contributions are not on Cc.

Thanks for letting know. Will be patient while the patch is being reviewed.

Best,
Chengfeng

2023-07-19 09:01:26

by Lee Jones

[permalink] [raw]
Subject: Re: [PATCH] mfd: qcom-pm8xxx: Fix potential deadlock on &chip->pm_irq_lock

On Tue, 18 Jul 2023, Chengfeng Ye wrote:

> > This is very old code that you're changing and some of the people who
> > made the largest contributions are not on Cc.
>
> Thanks for letting know. Will be patient while the patch is being reviewed.

No, I need you to resubmit it with more historical people on Cc please.

`git log --full-diff` should help you trace back through name changes.

--
Lee Jones [李琼斯]

2023-07-19 15:28:23

by Bjorn Andersson

[permalink] [raw]
Subject: Re: [PATCH] mfd: qcom-pm8xxx: Fix potential deadlock on &chip->pm_irq_lock

On Wed, Jun 28, 2023 at 07:28:40AM +0000, Chengfeng Ye wrote:
> As &chip->pm_irq_lock is acquired by pm8xxx_irq_handler() under irq
> context, other process context code should disable irq before acquiring
> the lock.
>
> I think .irq_set_type and .irq_get_irqchip_state callbacks should be

You are correct, so please drop "I think", and change "should be" to
"are generally".

> executed from process context without irq disabled by default. Thus the
> same lock acquision should disable irq.
>
> Possible deadlock scenario
> pm8xxx_irq_set_type()
> -> pm8xxx_config_irq()
> -> spin_lock(&chip->pm_irq_lock)
> <irq interrupt>
> -> pm8xxx_irq_handler()
> -> pm8xxx_irq_master_handler()
> -> pm8xxx_irq_block_handler()
> -> pm8xxx_read_block_irq()
> -> spin_lock(&chip->pm_irq_lock) (deadlock here)
>
> This flaw was found using an experimental static analysis tool we are
> developing for irq-related deadlock.
>
> The tentative patch fix the potential deadlock by spin_lock_irqsave().

I don't think this is a "tentative patch fix", it is the patch to fix
the issue. I think you can omit this line, because you already described
your problem, and the solution above.

>
> Signed-off-by: Chengfeng Ye <[email protected]>

Reviewed-by: Bjorn Andersson <[email protected]>

Regards,
Bjorn

2023-07-20 08:01:36

by Chengfeng Ye

[permalink] [raw]
Subject: Re: [PATCH] mfd: qcom-pm8xxx: Fix potential deadlock on &chip->pm_irq_lock

> You are correct, so please drop "I think", and change "should be" to
> "are generally"
> I don't think this is a "tentative patch fix", it is the patch to fix
> the issue. I think you can omit this line, because you already described
> your problem, and the solution above.
The V2 patch was just sent to address the problem.

> Reviewed-by: Bjorn Andersson <[email protected]>
Also thanks for your time in reviewing the patch :)

> No, I need you to resubmit it with more historical people on Cc please.
Thanks for the reminder, I Cc more people with large contributions to the
file in the V2 patch.

Best Regards,
Chengfeng