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Date:   Thu, 28 Jul 2022 09:17:54 -0400
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Subject: Re: [PATCH] SUNRPC: mutexed access blacklist_read state variable.
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To:     Attila Kovacs <attila.kovacs@cfa.harvard.edu>,
        Libtirpc-devel Mailing List 
        <libtirpc-devel@lists.sourceforge.net>
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References: <20220726201243.103800-1-attila.kovacs@cfa.harvard.edu>
From:   Steve Dickson <steved@redhat.com>
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On 7/26/22 4:12 PM, Attila Kovacs wrote:
> From: Attila Kovacs <attipaci@gmail.com>
> 
> bindresvport()_sa(), in bidresvport.c checks blacklist_read w/o mutex
> before calling load_blacklist() which changes blacklist_read() also
> unmutexed.
> 
> Clearly, the point is to read the blacklist only once on the first call,
> but because the checking whether the blacklist is loaded is not mutexed,
> more than one thread may race to load the blacklist concurrently, which
> of course can jumble the list because of the race condition.
> 
> The fix simply moves the checking within the mutexed aread of the code
> to eliminate the race condition.
Committed (tag: libtirpc-1-3-3-rc4)

steved.
> 
> ---
>   src/bindresvport.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/src/bindresvport.c b/src/bindresvport.c
> index ef9b345..5c0ddcf 100644
> --- a/src/bindresvport.c
> +++ b/src/bindresvport.c
> @@ -164,10 +164,11 @@ bindresvport_sa(sd, sa)
>   	int endport = ENDPORT;
>   	int i;
>   
> +	mutex_lock(&port_lock);
> +
>   	if (!blacklist_read)
>   		load_blacklist();
>   
> -	mutex_lock(&port_lock);
>   	nports = ENDPORT - startport + 1;
>   
>           if (sa == NULL) {