linux-kernel - Re: [PATCH v2] mfd: stmfx: Uninitialized variable in stmfx_irq

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Date:   Thu, 6 Jun 2019 12:56:38 +0000
From:   Amelie DELAUNAY <amelie.delaunay@...com>
To:     Dan Carpenter <dan.carpenter@...cle.com>,
        Lee Jones <lee.jones@...aro.org>
CC:     Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Alexandre TORGUE <alexandre.torgue@...com>,
        "linux-stm32@...md-mailman.stormreply.com" 
        <linux-stm32@...md-mailman.stormreply.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "kernel-janitors@...r.kernel.org" <kernel-janitors@...r.kernel.org>
Subject: Re: [PATCH v2] mfd: stmfx: Uninitialized variable in
 stmfx_irq_handler()

On 6/6/19 2:41 PM, Dan Carpenter wrote:
> The problem is that on 64bit systems then we don't clear the higher
> bits of the "pending" variable.  So when we do:
> 
>          ack = pending & ~BIT(STMFX_REG_IRQ_SRC_EN_GPIO);
>          if (ack) {
> 
> the if (ack) condition relies on uninitialized data.  The fix it that
> I've changed "pending" from an unsigned long to a u32.  I changed "n" as
> well, because that's a number in the 0-10 range and it fits easily
> inside an int.  We do need to add a cast to "pending" when we use it in
> the for_each_set_bit() loop, but that doesn't cause a proble, it's
> fine.
> 
> Fixes: 06252ade9156 ("mfd: Add ST Multi-Function eXpander (STMFX) core driver")
> Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>

Acked-by: Amelie Delaunay <amelie.delaunay@...com>

> ---
> v2: white space changes
> 
>   drivers/mfd/stmfx.c | 10 ++++------
>   1 file changed, 4 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/mfd/stmfx.c b/drivers/mfd/stmfx.c
> index fe8efba2d45f..7c419c078688 100644
> --- a/drivers/mfd/stmfx.c
> +++ b/drivers/mfd/stmfx.c
> @@ -204,12 +204,10 @@ static struct irq_chip stmfx_irq_chip = {
>   static irqreturn_t stmfx_irq_handler(int irq, void *data)
>   {
>   	struct stmfx *stmfx = data;
> -	unsigned long n, pending;
> -	u32 ack;
> -	int ret;
> +	u32 pending, ack;
> +	int n, ret;
>   
> -	ret = regmap_read(stmfx->map, STMFX_REG_IRQ_PENDING,
> -			  (u32 *)&pending);
> +	ret = regmap_read(stmfx->map, STMFX_REG_IRQ_PENDING, &pending);
>   	if (ret)
>   		return IRQ_NONE;
>   
> @@ -224,7 +222,7 @@ static irqreturn_t stmfx_irq_handler(int irq, void *data)
>   			return IRQ_NONE;
>   	}
>   
> -	for_each_set_bit(n, &pending, STMFX_REG_IRQ_SRC_MAX)
> +	for_each_set_bit(n, (unsigned long *)&pending, STMFX_REG_IRQ_SRC_MAX)
>   		handle_nested_irq(irq_find_mapping(stmfx->irq_domain, n));
>   
>   	return IRQ_HANDLED;
>