linux-kernel - Re: [PATCH v1] driver/base/memory.c: Validate memory block size early

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Date:   Tue, 6 Aug 2019 11:26:49 +0200
From:   David Hildenbrand <david@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     linux-mm@...ck.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Pavel Tatashin <pasha.tatashin@...een.com>,
        Michal Hocko <mhocko@...e.com>,
        Dan Williams <dan.j.williams@...el.com>
Subject: Re: [PATCH v1] driver/base/memory.c: Validate memory block size early

On 06.08.19 11:01, David Hildenbrand wrote:

"s/driver/drivers/" in subject.

I think long term, we should move the whole memory block size
configuration (set_memory_block_size_order() and
memory_block_size_bytes()) into drivers/base/memory.c.

> Let's validate the memory block size early, when initializing the
> memory device infrastructure. Fail hard in case the value is not
> suitable.
> 
> As nobody checks the return value of memory_dev_init(), turn it into a
> void function and fail with a panic in all scenarios instead. Otherwise,
> we'll crash later during boot when core/drivers expect that the memory
> device infrastructure (including memory_block_size_bytes()) works as
> expected.
> 
> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> Cc: "Rafael J. Wysocki" <rafael@...nel.org>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Pavel Tatashin <pasha.tatashin@...een.com>
> Cc: Michal Hocko <mhocko@...e.com>
> Cc: Dan Williams <dan.j.williams@...el.com>
> Signed-off-by: David Hildenbrand <david@...hat.com>
> ---
>  drivers/base/memory.c  | 31 +++++++++----------------------
>  include/linux/memory.h |  6 +++---
>  2 files changed, 12 insertions(+), 25 deletions(-)
> 
> diff --git a/drivers/base/memory.c b/drivers/base/memory.c
> index 790b3bcd63a6..6bea4f3f8040 100644
> --- a/drivers/base/memory.c
> +++ b/drivers/base/memory.c
> @@ -100,21 +100,6 @@ unsigned long __weak memory_block_size_bytes(void)
>  }
>  EXPORT_SYMBOL_GPL(memory_block_size_bytes);
>  
> -static unsigned long get_memory_block_size(void)
> -{
> -	unsigned long block_sz;
> -
> -	block_sz = memory_block_size_bytes();
> -
> -	/* Validate blk_sz is a power of 2 and not less than section size */
> -	if ((block_sz & (block_sz - 1)) || (block_sz < MIN_MEMORY_BLOCK_SIZE)) {
> -		WARN_ON(1);
> -		block_sz = MIN_MEMORY_BLOCK_SIZE;
> -	}
> -
> -	return block_sz;
> -}
> -
>  /*
>   * Show the first physical section index (number) of this memory block.
>   */
> @@ -461,7 +446,7 @@ static DEVICE_ATTR_RO(removable);
>  static ssize_t block_size_bytes_show(struct device *dev,
>  				     struct device_attribute *attr, char *buf)
>  {
> -	return sprintf(buf, "%lx\n", get_memory_block_size());
> +	return sprintf(buf, "%lx\n", memory_block_size_bytes());
>  }
>  
>  static DEVICE_ATTR_RO(block_size_bytes);
> @@ -811,19 +796,22 @@ static const struct attribute_group *memory_root_attr_groups[] = {
>  /*
>   * Initialize the sysfs support for memory devices...
>   */
> -int __init memory_dev_init(void)
> +void __init memory_dev_init(void)
>  {
>  	int ret;
>  	int err;
>  	unsigned long block_sz, nr;
>  
> +	/* Validate the configured memory block size */
> +	block_sz = memory_block_size_bytes();
> +	if (!is_power_of_2(block_sz) || block_sz < MIN_MEMORY_BLOCK_SIZE)
> +		panic("Memory block size not suitable: 0x%lx\n", block_sz);
> +	sections_per_block = block_sz / MIN_MEMORY_BLOCK_SIZE;
> +
>  	ret = subsys_system_register(&memory_subsys, memory_root_attr_groups);
>  	if (ret)
>  		goto out;
>  
> -	block_sz = get_memory_block_size();
> -	sections_per_block = block_sz / MIN_MEMORY_BLOCK_SIZE;
> -
>  	/*
>  	 * Create entries for memory sections that were found
>  	 * during boot and have been initialized
> @@ -839,8 +827,7 @@ int __init memory_dev_init(void)
>  
>  out:
>  	if (ret)
> -		printk(KERN_ERR "%s() failed: %d\n", __func__, ret);
> -	return ret;
> +		panic("%s() failed: %d\n", __func__, ret);
>  }
>  
>  /**
> diff --git a/include/linux/memory.h b/include/linux/memory.h
> index 704215d7258a..0ebb105eb261 100644
> --- a/include/linux/memory.h
> +++ b/include/linux/memory.h
> @@ -79,9 +79,9 @@ struct mem_section;
>  #define IPC_CALLBACK_PRI        10
>  
>  #ifndef CONFIG_MEMORY_HOTPLUG_SPARSE
> -static inline int memory_dev_init(void)
> +static inline void memory_dev_init(void)
>  {
> -	return 0;
> +	return;
>  }
>  static inline int register_memory_notifier(struct notifier_block *nb)
>  {
> @@ -112,7 +112,7 @@ extern int register_memory_isolate_notifier(struct notifier_block *nb);
>  extern void unregister_memory_isolate_notifier(struct notifier_block *nb);
>  int create_memory_block_devices(unsigned long start, unsigned long size);
>  void remove_memory_block_devices(unsigned long start, unsigned long size);
> -extern int memory_dev_init(void);
> +extern void memory_dev_init(void);
>  extern int memory_notify(unsigned long val, void *v);
>  extern int memory_isolate_notify(unsigned long val, void *v);
>  extern struct memory_block *find_memory_block(struct mem_section *);
> 


-- 

Thanks,

David / dhildenb