linux-kernel - Re: [PATCH] kprobes: x86_64: blacklist non-attachable interrupt functions

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Date:   Fri, 7 Dec 2018 18:00:26 +0100
From:   Andrea Righi <righi.andrea@...il.com>
To:     Masami Hiramatsu <mhiramat@...nel.org>
Cc:     "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>,
        Anil S Keshavamurthy <anil.s.keshavamurthy@...el.com>,
        "David S. Miller" <davem@...emloft.net>,
        Yonghong Song <yhs@...com>, Andy Lutomirski <luto@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] kprobes: x86_64: blacklist non-attachable interrupt
 functions

On Sat, Dec 08, 2018 at 01:01:20AM +0900, Masami Hiramatsu wrote:
> Hi Andrea and Ingo,
> 
> Here is the patch what I meant. I just ran it on qemu-x86, and seemed working.
> After introducing this patch, I will start adding arch_populate_kprobe_blacklist()
> to some arches.
> 
> Thank you,
> 
> [RFC] kprobes: x86/kprobes: Blacklist symbols in arch-defined prohibited area
> 
> From: Masami Hiramatsu <mhiramat@...nel.org>
> 
> Blacklist symbols in arch-defined probe-prohibited areas.
> With this change, user can see all symbols which are prohibited
> to probe in debugfs.
> 
> All archtectures which have custom prohibit areas should define
> its own arch_populate_kprobe_blacklist() function, but unless that,
> all symbols marked __kprobes are blacklisted.
> 
> Reported-by: Andrea Righi <righi.andrea@...il.com>
> Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
> ---

[snip]

> +int kprobe_add_ksym_blacklist(unsigned long entry)
> +{
> +	struct kprobe_blacklist_entry *ent;
> +	unsigned long offset = 0, size = 0;
> +
> +	if (!kernel_text_address(entry) ||
> +	    !kallsyms_lookup_size_offset(entry, &size, &offset))
> +		return -EINVAL;
> +
> +	ent = kmalloc(sizeof(*ent), GFP_KERNEL);
> +	if (!ent)
> +		return -ENOMEM;
> +	ent->start_addr = entry - offset;
> +	ent->end_addr = entry - offset + size;

Do we need to take offset into account? The code before wasn't using it.

> +	INIT_LIST_HEAD(&ent->list);
> +	list_add_tail(&ent->list, &kprobe_blacklist);
> +
> +	return (int)size;
> +}
> +
> +/* Add functions in arch defined probe-prohibited area */
> +int __weak arch_populate_kprobe_blacklist(void)
> +{
> +	unsigned long entry;
> +	int ret = 0;
> +
> +	for (entry = (unsigned long)__kprobes_text_start;
> +	     entry < (unsigned long)__kprobes_text_end;
> +	     entry += ret) {
> +		ret = kprobe_add_ksym_blacklist(entry);
> +		if (ret < 0)
> +			return ret;
> +		if (ret == 0)	/* In case of alias symbol */
> +			ret = 1;
> +	}
> +	return 0;
> +}
> +
>  /*
>   * Lookup and populate the kprobe_blacklist.
>   *
> @@ -2104,26 +2142,20 @@ NOKPROBE_SYMBOL(dump_kprobe);
>  static int __init populate_kprobe_blacklist(unsigned long *start,
>  					     unsigned long *end)
>  {
> +	unsigned long entry;
>  	unsigned long *iter;
> -	struct kprobe_blacklist_entry *ent;
> -	unsigned long entry, offset = 0, size = 0;
> +	int ret;
>  
>  	for (iter = start; iter < end; iter++) {
>  		entry = arch_deref_entry_point((void *)*iter);
> -
> -		if (!kernel_text_address(entry) ||
> -		    !kallsyms_lookup_size_offset(entry, &size, &offset))
> +		ret = kprobe_add_ksym_blacklist(entry);
> +		if (ret == -EINVAL)
>  			continue;
> -
> -		ent = kmalloc(sizeof(*ent), GFP_KERNEL);
> -		if (!ent)
> -			return -ENOMEM;
> -		ent->start_addr = entry;
> -		ent->end_addr = entry + size;
> -		INIT_LIST_HEAD(&ent->list);
> -		list_add_tail(&ent->list, &kprobe_blacklist);
> +		if (ret < 0)
> +			return ret;
>  	}
> -	return 0;
> +
> +	return arch_populate_kprobe_blacklist();
>  }
>  
>  /* Module notifier call back, checking kprobes on the module */