netdev - Re: [PATCH bpf-next] bpf, xskmap: fix crash in xsk_map

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Date:   Fri, 04 May 2018 11:39:20 -0400 (EDT)
From:   David Miller <davem@...emloft.net>
To:     daniel@...earbox.net
Cc:     alexei.starovoitov@...il.com, netdev@...r.kernel.org,
        bjorn.topel@...el.com
Subject: Re: [PATCH bpf-next] bpf, xskmap: fix crash in xsk_map_alloc error
 path handling

From: Daniel Borkmann <daniel@...earbox.net>
Date: Fri,  4 May 2018 16:27:53 +0200

> If bpf_map_precharge_memlock() did not fail, then we set err to zero.
> However, any subsequent failure from either alloc_percpu() or the
> bpf_map_area_alloc() will return ERR_PTR(0) which in find_and_alloc_map()
> will cause NULL pointer deref.
> 
> In devmap we have the convention that we return -EINVAL on page count
> overflow, so keep the same logic here and just set err to -ENOMEM
> after successful bpf_map_precharge_memlock().
> 
> Fixes: fbfc504a24f5 ("bpf: introduce new bpf AF_XDP map type BPF_MAP_TYPE_XSKMAP")
> Signed-off-by: Daniel Borkmann <daniel@...earbox.net>

Acked-by: David S. Miller <davem@...emloft.net>