netdev - Re: [PATCH net] bpf/xskmap: Return ERR_PTR for failure case instead of NULL.

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Message-ID: <5f85df65-0f2e-3533-9734-147b0734e254@intel.com>
Date:   Tue, 24 Sep 2019 21:30:44 +0200
From:   Björn Töpel <bjorn.topel@...el.com>
To:     Jonathan Lemon <jonathan.lemon@...il.com>, daniel@...earbox.net,
        netdev@...r.kernel.org, Alexei Starovoitov <ast@...nel.org>
Cc:     kernel-team@...com, bpf <bpf@...r.kernel.org>,
        "Karlsson, Magnus" <magnus.karlsson@...el.com>,
        syzkaller-bugs@...glegroups.com,
        syzbot+491c1b7565ba9069ecae@...kaller.appspotmail.com
Subject: Re: [PATCH net] bpf/xskmap: Return ERR_PTR for failure case instead
 of NULL.

On 2019-09-24 18:25, Jonathan Lemon wrote:
> When kzalloc() failed, NULL was returned to the caller, which
> tested the pointer with IS_ERR(), which didn't match, so the
> pointer was used later, resulting in a NULL dereference.
> 
> Return ERR_PTR(-ENOMEM) instead of NULL.
> 
> Reported-by: syzbot+491c1b7565ba9069ecae@...kaller.appspotmail.com
> Fixes: 0402acd683c6 ("xsk: remove AF_XDP socket from map when the socket is released")
> Signed-off-by: Jonathan Lemon <jonathan.lemon@...il.com>

Thanks Jonathan! You beat me to it! :-P

Acked-by: Björn Töpel <bjorn.topel@...el.com>

> ---
>   kernel/bpf/xskmap.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/bpf/xskmap.c b/kernel/bpf/xskmap.c
> index 942c662e2eed..82a1ffe15dfa 100644
> --- a/kernel/bpf/xskmap.c
> +++ b/kernel/bpf/xskmap.c
> @@ -37,7 +37,7 @@ static struct xsk_map_node *xsk_map_node_alloc(struct xsk_map *map,
>   
>   	node = kzalloc(sizeof(*node), GFP_ATOMIC | __GFP_NOWARN);
>   	if (!node)
> -		return NULL;
> +		return ERR_PTR(-ENOMEM);
>   
>   	err = xsk_map_inc(map);
>   	if (err) {
>