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

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

[Chengfeng Ye]

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 <dg573847474@gmail.com>
---
 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

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

[Lee Jones]

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 <dg573847474@gmail.com>
> ---
>  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]

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

[Chengfeng Ye]

> 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

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

[Lee Jones]

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]

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

[Bjorn Andersson]

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 <dg573847474@gmail.com>

Reviewed-by: Bjorn Andersson <quic_bjorande@quicinc.com>

Regards,
Bjorn

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

[Chengfeng Ye]

 > 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 <quic_bjorande@quicinc.com>
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