linux-kernel - Re: [PATCH v2] irqchip/gicv3-its: Don't allow devices whose ID is outside range

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Date:	Wed, 9 Mar 2016 02:31:16 +0000
From:	Marc Zyngier <marc.zyngier@....com>
To:	Shanker Donthineni <shankerd@...eaurora.org>
Cc:	<linux-arm-kernel@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>,
	Vikram Sethi <vikrams@...eaurora.org>,
	Jason Cooper <jason@...edaemon.net>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH v2] irqchip/gicv3-its: Don't allow devices whose ID is
 outside range

On Sun, 28 Feb 2016 13:22:03 -0600
Shanker Donthineni <shankerd@...eaurora.org> wrote:

Hi Shanker,

> We are not checking whether the requested device identifier fits into
> the device table memory or not. The function its_create_device()
> assumes that enough memory has been allocated for whole DevID sparse
> (reported by ITS_TYPER.Devbits) during the ITS probe() and continues
> to initialize ITS hardware.
> 
> This assumption is not perfect, sometimes we reduce memory size either
> because of its size crossing MAX_ORDER-1 or BASERn max size limit. The
> MAPD command fails if 'Device ID' is outside of device table range.
> 
> Add a simple validation check to avoid MAPD failures since we are
> not handling ITS command errors. This change also helps to return an
> error -ENOMEM instead of success to caller.
> 
> Signed-off-by: Shanker Donthineni <shankerd@...eaurora.org>
> ---
> [v1]->[v2]
>   Rebase to v4.5-rc6, edit commit text and simplify code changes
> 
>  drivers/irqchip/irq-gic-v3-its.c | 24 ++++++++++++++++++++----
>  1 file changed, 20 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c
> index 43dfd15..6d986ac 100644
> --- a/drivers/irqchip/irq-gic-v3-its.c
> +++ b/drivers/irqchip/irq-gic-v3-its.c
> @@ -55,6 +55,16 @@ struct its_collection {
>  };
>  
>  /*
> + * The ITS_BASER structure - contains memeory information and table
> + * entry size in bytes.
> + */
> +struct its_baser {
> +	void		*base;
> +	u32		order;
> +	u32		entry_size;
> +};
> +
> +/*
>   * The ITS structure - contains most of the infrastructure, with the
>   * top-level MSI domain, the command queue, the collections, and the
>   * list of devices writing to it.
> @@ -66,14 +76,12 @@ struct its_node {
>  	unsigned long		phys_base;
>  	struct its_cmd_block	*cmd_base;
>  	struct its_cmd_block	*cmd_write;
> -	struct {
> -		void		*base;
> -		u32		order;
> -	} tables[GITS_BASER_NR_REGS];
> +	struct its_baser	tables[GITS_BASER_NR_REGS];
>  	struct its_collection	*collections;
>  	struct list_head	its_device_list;
>  	u64			flags;
>  	u32			ite_size;
> +	struct its_baser	*device_table;

nit: grouping this field with the tables array would make it slightly
nicer.

>  };
>  
>  #define ITS_ITT_ALIGN		SZ_256
> @@ -860,6 +868,7 @@ static int its_alloc_tables(const char *node_name, struct its_node *its)
>  		 * For other tables, only allocate a single page.
>  		 */
>  		if (type == GITS_BASER_TYPE_DEVICE) {
> +			its->device_table = &its->tables[i];
>  			/*
>  			 * 'order' was initialized earlier to the default page
>  			 * granule of the the ITS.  We can't have an allocation
> @@ -874,6 +883,7 @@ static int its_alloc_tables(const char *node_name, struct its_node *its)
>  					node_name, order);
>  			}
>  		}
> +		its->tables[i].entry_size = entry_size;
>  
>  retry_alloc_baser:
>  		alloc_pages = (PAGE_ORDER_TO_SIZE(order) / psz);
> @@ -1152,6 +1162,12 @@ static struct its_device *its_create_device(struct its_node *its, u32 dev_id,
>  	int nr_ites;
>  	int sz;
>  
> +	/* Don't allow 'dev_id' that exceeds single, flat table limit */
> +	if (its->device_table &&
> +	    (dev_id >= (PAGE_ORDER_TO_SIZE(its->device_table->order) /
> +	    its->device_table->entry_size)))

Assume for a minute we do not have a device table (which would be
perfectly possible - just think of an ITS with its own private memory,
like we have with KVM). Shouldn't we also check devid with the number of
bits that this ITS implements for Device IDs?

> +		return NULL;
> +
>  	dev = kzalloc(sizeof(*dev), GFP_KERNEL);
>  	/*
>  	 * At least one bit of EventID is being used, hence a minimum

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny.