netdev - Re: [PATCH net] net, neigh: clear whole pneigh

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Date:   Wed, 8 Dec 2021 08:53:57 -0700
From:   David Ahern <dsahern@...il.com>
To:     Eric Dumazet <eric.dumazet@...il.com>,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     netdev <netdev@...r.kernel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Roopa Prabhu <roopa@...dia.com>
Subject: Re: [PATCH net] net, neigh: clear whole pneigh_entry at alloc time

On 12/6/21 9:53 AM, Eric Dumazet wrote:
> From: Eric Dumazet <edumazet@...gle.com>
> 
> Commit 2c611ad97a82 ("net, neigh: Extend neigh->flags to 32 bit
> to allow for extensions") enables a new KMSAM warning [1]
> 
> I think the bug is actually older, because the following intruction
> only occurred if ndm->ndm_flags had NTF_PROXY set.
> 
> 	pn->flags = ndm->ndm_flags;
> 
> Let's clear all pneigh_entry fields at alloc time.
> 

All of the fields - except the new flags field - are initialized after
the alloc. Why do you think the bug is older?

...

> Fixes: 62dd93181aaa ("[IPV6] NDISC: Set per-entry is_router flag in Proxy NA.")
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Cc: Roopa Prabhu <roopa@...dia.com>
> ---
>  net/core/neighbour.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/net/core/neighbour.c b/net/core/neighbour.c
> index 72ba027c34cfea6f38a9e78927c35048ebfe7a7f..dda12fbd177ba6ad2798ea2b07733fa3f03441ab 100644
> --- a/net/core/neighbour.c
> +++ b/net/core/neighbour.c
> @@ -763,11 +763,10 @@ struct pneigh_entry * pneigh_lookup(struct neigh_table *tbl,
>  
>  	ASSERT_RTNL();
>  
> -	n = kmalloc(sizeof(*n) + key_len, GFP_KERNEL);
> +	n = kzalloc(sizeof(*n) + key_len, GFP_KERNEL);
>  	if (!n)
>  		goto out;
>  
> -	n->protocol = 0;
>  	write_pnet(&n->net, net);
>  	memcpy(n->key, pkey, key_len);
>  	n->dev = dev;
> 

Reviewed-by: David Ahern <dsahern@...nel.org>