netdev - Re: [PATCH 1/4] tipc: Fix bugs in tipc_msg_calc_data

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Date:	Thu, 28 Oct 2010 10:07:11 -0400
From:	Neil Horman <nhorman@...driver.com>
To:	Paul Gortmaker <paul.gortmaker@...driver.com>
Cc:	davem@...emloft.net, netdev@...r.kernel.org,
	allan.stephens@...driver.com, drosenberg@...curity.com,
	jon.maloy@...csson.com, torvalds@...ux-foundation.org,
	security@...nel.org
Subject: Re: [PATCH 1/4] tipc: Fix bugs in tipc_msg_calc_data_size()

On Wed, Oct 27, 2010 at 03:29:30PM -0400, Paul Gortmaker wrote:
> From: Allan Stephens <Allan.Stephens@...driver.com>
> 
> Enhances TIPC's computation of the amount of data to be sent so that
> it works properly when large values are involved. Calculations are now
> done using "size_t" instead of "int", and a check has been added to
> handle cases where the total amount of data exceeds the range of "size_t".
> 
> Signed-off-by: Allan Stephens <Allan.Stephens@...driver.com>
> ---
>  net/tipc/msg.c |   17 ++++++++++++-----
>  net/tipc/msg.h |    2 +-
>  2 files changed, 13 insertions(+), 6 deletions(-)
> 
> diff --git a/net/tipc/msg.c b/net/tipc/msg.c
> index ecb532f..38360a9 100644
> --- a/net/tipc/msg.c
> +++ b/net/tipc/msg.c
> @@ -72,15 +72,22 @@ void tipc_msg_init(struct tipc_msg *m, u32 user, u32 type,
>  
>  /**
>   * tipc_msg_calc_data_size - determine total data size for message
> + *
> + * Note: If total exceeds range of size_t returns largest possible value
>   */
>  
> -int tipc_msg_calc_data_size(struct iovec const *msg_sect, u32 num_sect)
> +size_t tipc_msg_calc_data_size(struct iovec const *msg_sect, size_t num_sect)
>  {
> -	int dsz = 0;
> -	int i;
> +	size_t dsz = 0;
> +	size_t len;
> +	size_t i;
>  
> -	for (i = 0; i < num_sect; i++)
> -		dsz += msg_sect[i].iov_len;
> +	for (i = 0; i < num_sect; i++) {
> +		len = msg_sect[i].iov_len;
> +		if (len > (size_t)LONG_MAX - dsz)
> +			return (size_t)LONG_MAX;
> +		dsz += len;
> +	}
>  	return dsz;
>  }
>  
> diff --git a/net/tipc/msg.h b/net/tipc/msg.h
> index 031aad1..a132800 100644
> --- a/net/tipc/msg.h
> +++ b/net/tipc/msg.h
> @@ -711,7 +711,7 @@ static inline void msg_set_dataoctet(struct tipc_msg *m, u32 pos)
>  u32 tipc_msg_tot_importance(struct tipc_msg *m);
>  void tipc_msg_init(struct tipc_msg *m, u32 user, u32 type,
>  			    u32 hsize, u32 destnode);
> -int tipc_msg_calc_data_size(struct iovec const *msg_sect, u32 num_sect);
> +size_t tipc_msg_calc_data_size(struct iovec const *msg_sect, size_t num_sect);
>  int tipc_msg_build(struct tipc_msg *hdr,
>  			    struct iovec const *msg_sect, u32 num_sect,
>  			    int max_size, int usrmem, struct sk_buff** buf);
> -- 
> 1.7.1.GIT
> 
You should probably roll this patch together with your second one.  The caller
tipc_msg_build will otherwise throw a warning when you build, as it assigns the
return value with this patch (a size_t) to a signed integer.  It probably won't
matter since you limit dsz to TIPC_MAX_USER_MSG_SIZE which is small in
comparison to the size of an int, but nevertheless, the two patches are related,
so you can merge them.

Neil

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