linux-kernel - Re: [PATCH v2] tipc: Avoid copying bytes beyond the supplied data

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Date:   Wed, 22 May 2019 15:47:46 +0800
From:   Ying Xue <ying.xue@...driver.com>
To:     Chris Packham <chris.packham@...iedtelesis.co.nz>,
        <jon.maloy@...csson.com>, <davem@...emloft.net>,
        <niveditas98@...il.com>
CC:     <netdev@...r.kernel.org>, <tipc-discussion@...ts.sourceforge.net>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] tipc: Avoid copying bytes beyond the supplied data

On 5/20/19 11:45 AM, Chris Packham wrote:
> TLV_SET is called with a data pointer and a len parameter that tells us
> how many bytes are pointed to by data. When invoking memcpy() we need
> to careful to only copy len bytes.
> 
> Previously we would copy TLV_LENGTH(len) bytes which would copy an extra
> 4 bytes past the end of the data pointer which newer GCC versions
> complain about.
> 
>  In file included from test.c:17:
>  In function 'TLV_SET',
>      inlined from 'test' at test.c:186:5:
>  /usr/include/linux/tipc_config.h:317:3:
>  warning: 'memcpy' forming offset [33, 36] is out of the bounds [0, 32]
>  of object 'bearer_name' with type 'char[32]' [-Warray-bounds]
>      memcpy(TLV_DATA(tlv_ptr), data, tlv_len);
>      ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>  test.c: In function 'test':
>  test.c::161:10: note:
>  'bearer_name' declared here
>      char bearer_name[TIPC_MAX_BEARER_NAME];
>           ^~~~~~~~~~~
> 
> We still want to ensure any padding bytes at the end are initialised, do
> this with a explicit memset() rather than copy bytes past the end of
> data. Apply the same logic to TCM_SET.
> 
> Signed-off-by: Chris Packham <chris.packham@...iedtelesis.co.nz>

Acked-by: Ying Xue <ying.xue@...driver.com>


But please make the same changes in usr/include/linux/tipc_config.h

> ---
> 
> Changes in v2:
> - Ensure padding bytes are initialised in both TLV_SET and TCM_SET
> 
>  include/uapi/linux/tipc_config.h | 10 +++++++---
>  1 file changed, 7 insertions(+), 3 deletions(-)
> 
> diff --git a/include/uapi/linux/tipc_config.h b/include/uapi/linux/tipc_config.h
> index 4b2c93b1934c..4955e1a9f1bc 100644
> --- a/include/uapi/linux/tipc_config.h
> +++ b/include/uapi/linux/tipc_config.h
> @@ -307,8 +307,10 @@ static inline int TLV_SET(void *tlv, __u16 type, void *data, __u16 len)
>  	tlv_ptr = (struct tlv_desc *)tlv;
>  	tlv_ptr->tlv_type = htons(type);
>  	tlv_ptr->tlv_len  = htons(tlv_len);
> -	if (len && data)
> -		memcpy(TLV_DATA(tlv_ptr), data, tlv_len);
> +	if (len && data) {
> +		memcpy(TLV_DATA(tlv_ptr), data, len);
> +		memset(TLV_DATA(tlv_ptr) + len, 0, TLV_SPACE(len) - tlv_len);
> +	}
>  	return TLV_SPACE(len);
>  }
>  
> @@ -405,8 +407,10 @@ static inline int TCM_SET(void *msg, __u16 cmd, __u16 flags,
>  	tcm_hdr->tcm_len   = htonl(msg_len);
>  	tcm_hdr->tcm_type  = htons(cmd);
>  	tcm_hdr->tcm_flags = htons(flags);
> -	if (data_len && data)
> +	if (data_len && data) {
>  		memcpy(TCM_DATA(msg), data, data_len);
> +		memset(TCM_DATA(msg) + data_len, 0, TCM_SPACE(data_len) - msg_len);
> +	}
>  	return TCM_SPACE(data_len);
>  }
>  
>