linux-kernel - Re: [PATCH] livepatch: Validate module/old func name length

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Date:   Fri, 20 Jul 2018 12:20:51 -0500
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Kamalesh Babulal <kamalesh@...ux.vnet.ibm.com>
Cc:     Petr Mladek <pmladek@...e.com>, Miroslav Benes <mbenes@...e.cz>,
        Jiri Kosina <jikos@...nel.org>, live-patching@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] livepatch: Validate module/old func name length

On Fri, Jul 20, 2018 at 03:16:42PM +0530, Kamalesh Babulal wrote:
> livepatch module author can pass module name/old function name with more
> than the defined character limit. With obj->name length greater than
> MODULE_NAME_LEN, the livepatch module gets loaded but waits forever on
> the module specified by obj->name to be loaded. It also populates a /sys
> directory with an untruncated object name.
> 
> In the case of funcs->old_name length greater then KSYM_NAME_LEN, it
> would not match against any of the symbol table entries. Instead loop
> through the symbol table comparing them against a nonexisting function,
> which can be avoided.
> 
> The same issues apply, to misspelled/incorrect names. At least gatekeep
> the modules with over the limit string length, by checking for their
> length during livepatch module registration.
> 
> Signed-off-by: Kamalesh Babulal <kamalesh@...ux.vnet.ibm.com>

Acked-by: Josh Poimboeuf <jpoimboe@...hat.com>

> ---
>  kernel/livepatch/core.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
> index 3a4656fb7047..5b77a7314e01 100644
> --- a/kernel/livepatch/core.c
> +++ b/kernel/livepatch/core.c
> @@ -678,6 +678,9 @@ static int klp_init_func(struct klp_object *obj, struct klp_func *func)
>  	if (!func->old_name || !func->new_func)
>  		return -EINVAL;
>  
> +	if (strlen(func->old_name) >= KSYM_NAME_LEN)
> +		return -EINVAL;
> +
>  	INIT_LIST_HEAD(&func->stack_node);
>  	func->patched = false;
>  	func->transition = false;
> @@ -751,6 +754,9 @@ static int klp_init_object(struct klp_patch *patch, struct klp_object *obj)
>  	if (!obj->funcs)
>  		return -EINVAL;
>  
> +	if (klp_is_module(obj) && strlen(obj->name) >= MODULE_NAME_LEN)
> +		return -EINVAL;
> +
>  	obj->patched = false;
>  	obj->mod = NULL;
>  
> -- 
> 2.7.4
> 

-- 
Josh