netdev - Re: Freeing alive fib_info caused by ebc0ffae5

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Date:	Thu, 04 Nov 2010 22:35:26 +1100
From:	Michael Ellerman <michael@...erman.id.au>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	netdev@...r.kernel.org
Subject: Re: Freeing alive fib_info caused by ebc0ffae5

On Thu, 2010-11-04 at 12:21 +0100, Eric Dumazet wrote:
> 
> Hmm, a review of the code spotted a bug in fib_result_assign()
> 
> Please try following patch :
> 
> Thanks again !
> 
> [PATCH] fib: fib_result_assign() should not change fib refcounts
> 
> After commit ebc0ffae5 (RCU conversion of fib_lookup()),
> fib_result_assign()  should not change fib refcounts anymore.
> 
> Thanks to Michael who did the bisection and bug report.
> 
> Reported-by: Michael Ellerman <michael@...erman.id.au>
> Signed-off-by: Eric Dumazet <eric.dumazet@...il.com>
> ---
>  net/ipv4/fib_lookup.h |    5 +----
>  1 file changed, 1 insertion(+), 4 deletions(-)
> 
> diff --git a/net/ipv4/fib_lookup.h b/net/ipv4/fib_lookup.h
> index a29edf2..c079cc0 100644
> --- a/net/ipv4/fib_lookup.h
> +++ b/net/ipv4/fib_lookup.h
> @@ -47,11 +47,8 @@ extern int fib_detect_death(struct fib_info *fi, int order,
>  static inline void fib_result_assign(struct fib_result *res,
>  				     struct fib_info *fi)
>  {
> -	if (res->fi != NULL)
> -		fib_info_put(res->fi);
> +	/* we used to play games with refcounts, but we now use RCU */
>  	res->fi = fi;
> -	if (fi != NULL)
> -		atomic_inc(&fi->fib_clntref);
>  }
>  
>  #endif /* _FIB_LOOKUP_H */

Perfect, that fixes it, thanks!

cheers



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