linux-kernel - Re: [PATCH 2/2] livepatch: Fix the bug if the function name is larger than KSYM_NAME

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Message-ID: <20150413084450.GB16088@pathway.suse.cz>
Date:	Mon, 13 Apr 2015 10:44:50 +0200
From:	Petr Mladek <pmladek@...e.cz>
To:	Minfei Huang <minfei.huang@...mail.com>
Cc:	jpoimboe@...hat.com, sjenning@...hat.com, jkosina@...e.cz,
	vojtech@...e.cz, live-patching@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] livepatch: Fix the bug if the function name is
 larger than KSYM_NAME_LEN-1

On Sun 2015-04-12 21:15:54, Minfei Huang wrote:
> For now, the kallsyms will only store the first (KSYM_NAME_LEN-1). The
> kallsyms name is same for the function which first (KSYM_NAME_LEN-1) is
> same, but the rest is not.
> 
> Then function will never be patched, although function name and address
> are provided both. The reason caused this bug is livepatch cannt
> recognize the function name.
> 
> Now, livepatch will verify the function name with first (KSYM_NAME_LEN-1)
> and address, if provided. Once they are matched, we can confirm that the
> patched function is found.

This patch kind of make sense for vmlinux addresses. But are there
functions with such a long names (>128 characters)? I hope not. They
would never fit 80 characters per-line.

In each case, it does not make sense for modules because we are
not able to find the symbol via old_addr.

Best Regards,
Petr
 
> Signed-off-by: Minfei Huang <minfei.huang@...mail.com>
> ---
>  kernel/livepatch/core.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
> index ff42c29..eed719d 100644
> --- a/kernel/livepatch/core.c
> +++ b/kernel/livepatch/core.c
> @@ -210,7 +210,7 @@ static int klp_verify_vmlinux_callback(void *data, const char *name,
>  	struct klp_verify_args *args = data;
>  
>  	if (!mod &&
> -	    !strcmp(args->name, name) &&
> +	    !strncmp(args->name, name, KSYM_NAME_LEN-1) &&
>  	    args->addr == addr)
>  		return 1;
>  
> @@ -226,7 +226,7 @@ static int klp_verify_module_callback(void *data, const char *name,
>  		return 0;
>  
>  	if (!strcmp(args->objname, mod->name) &&
> -	    !strcmp(args->name, name) &&
> +	    !strncmp(args->name, name, KSYM_NAME_LEN-1) &&
>  	    args->addr == addr)
>  		return 1;
>  
> -- 
> 2.2.2
> 
> --
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