Re: [dpdk-dev] [PATCH v2] ip_frag: fix double free of chained mbufs

["Ananyev, Konstantin" <konstantin.ananyev@intel.com>]

Hi Allain,

> 
> The first mbuf and the last mbuf to be visited in the preceding loop
> are not set to NULL in the fragmentation table.  This creates the
> possibility of a double free when the fragmentation table is later freed
> with rte_ip_frag_table_destroy().
> 
> Fixes: 95908f52393d ("ip_frag: free mbufs on reassembly table destroy")
> 
> Signed-off-by: Allain Legacy <allain.legacy@windriver.com>
> ---
>  lib/librte_ip_frag/rte_ipv4_reassembly.c | 2 ++
>  lib/librte_ip_frag/rte_ipv6_reassembly.c | 2 ++
>  2 files changed, 4 insertions(+)
> 
> diff --git a/lib/librte_ip_frag/rte_ipv4_reassembly.c b/lib/librte_ip_frag/rte_ipv4_reassembly.c
> index 82e831ca3..4956b99ea 100644
> --- a/lib/librte_ip_frag/rte_ipv4_reassembly.c
> +++ b/lib/librte_ip_frag/rte_ipv4_reassembly.c
> @@ -59,7 +59,9 @@ ipv4_frag_reassemble(struct ip_frag_pkt *fp)
>  	/* chain with the first fragment. */
>  	rte_pktmbuf_adj(m, (uint16_t)(m->l2_len + m->l3_len));
>  	rte_pktmbuf_chain(fp->frags[IP_FIRST_FRAG_IDX].mb, m);
> +	fp->frags[curr_idx].mb = NULL;
>  	m = fp->frags[IP_FIRST_FRAG_IDX].mb;
> +	fp->frags[IP_FIRST_FRAG_IDX].mb = NULL;


I wonder why we have to NULL only first and cur entry?
We probably have to NULL each one in that case, right?
If so, then it probably better to do in the same place we do ip_frag_key_invalidate().
As alternative, and probably better approach - can we modify rte_ip_frag_table_destroy(),
so it will free mbufs only for entires with valid keys?
Konstantin 

> 
>  	/* update mbuf fields for reassembled packet. */
>  	m->ol_flags |= PKT_TX_IP_CKSUM;
> diff --git a/lib/librte_ip_frag/rte_ipv6_reassembly.c b/lib/librte_ip_frag/rte_ipv6_reassembly.c
> index 3479fabb8..db249fe60 100644
> --- a/lib/librte_ip_frag/rte_ipv6_reassembly.c
> +++ b/lib/librte_ip_frag/rte_ipv6_reassembly.c
> @@ -82,7 +82,9 @@ ipv6_frag_reassemble(struct ip_frag_pkt *fp)
>  	/* chain with the first fragment. */
>  	rte_pktmbuf_adj(m, (uint16_t)(m->l2_len + m->l3_len));
>  	rte_pktmbuf_chain(fp->frags[IP_FIRST_FRAG_IDX].mb, m);
> +	fp->frags[curr_idx].mb = NULL;
>  	m = fp->frags[IP_FIRST_FRAG_IDX].mb;
> +	fp->frags[IP_FIRST_FRAG_IDX].mb = NULL;
> 
>  	/* update mbuf fields for reassembled packet. */
>  	m->ol_flags |= PKT_TX_IP_CKSUM;
> --
> 2.12.1