netdev - Re: [PATCH net] sctp: use __GFP_NOWARN for sctpw.fifo allocation

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Message-ID: <20170805170859.GA7613@localhost.localdomain>
Date:   Sat, 5 Aug 2017 14:08:59 -0300
From:   Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
To:     Xin Long <lucien.xin@...il.com>
Cc:     network dev <netdev@...r.kernel.org>, linux-sctp@...r.kernel.org,
        davem@...emloft.net, Neil Horman <nhorman@...driver.com>
Subject: Re: [PATCH net] sctp: use __GFP_NOWARN for sctpw.fifo allocation

On Sat, Aug 05, 2017 at 08:31:09PM +0800, Xin Long wrote:
> Chen Wei found a kernel call trace when modprobe sctp_probe with
> bufsize set with a huge value.
> 
> It's because in sctpprobe_init when alloc memory for sctpw.fifo,
> the size is got from userspace. If it is too large, kernel will
> fail and give a warning.

Yes but sctp_probe can only be loaded by an admin and it would happen
only during modprobe. It's different from the commit mentioned below, on
which any user could trigger it.

> 
> As there will be a fallback allocation later, this patch is just
> to fail silently and return ret, just as commit 0ccc22f425e5
> ("sit: use __GFP_NOWARN for user controlled allocation") did.
> 
> Reported-by: Chen Wei <weichen@...hat.com>
> Signed-off-by: Xin Long <lucien.xin@...il.com>
> ---
>  net/sctp/probe.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/net/sctp/probe.c b/net/sctp/probe.c
> index 6cc2152..5bf3164 100644
> --- a/net/sctp/probe.c
> +++ b/net/sctp/probe.c
> @@ -210,7 +210,7 @@ static __init int sctpprobe_init(void)
>  
>  	init_waitqueue_head(&sctpw.wait);
>  	spin_lock_init(&sctpw.lock);
> -	if (kfifo_alloc(&sctpw.fifo, bufsize, GFP_KERNEL))
> +	if (kfifo_alloc(&sctpw.fifo, bufsize, GFP_KERNEL | __GFP_NOWARN))
>  		return ret;
>  
>  	if (!proc_create(procname, S_IRUSR, init_net.proc_net,
> -- 
> 2.1.0
> 
> --
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