linux-kernel - Re: [PATCH] nfsd: fix oops when reading pool

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Date: Mon, 17 Jun 2024 10:21:34 -0400
From: Chuck Lever <chuck.lever@...cle.com>
To: Jeff Layton <jlayton@...nel.org>
Cc: Sourabh Jain <sourabhjain@...ux.ibm.com>, Neil Brown <neilb@...e.de>,
        Olga Kornievskaia <kolga@...app.com>, Dai Ngo <Dai.Ngo@...cle.com>,
        Tom Talpey <tom@...pey.com>,
        Trond Myklebust <trond.myklebust@...merspace.com>,
        Anna Schumaker <anna@...nel.org>, linux-nfs@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] nfsd: fix oops when reading pool_stats before server is
 started

On Mon, Jun 17, 2024 at 07:54:08AM -0400, Jeff Layton wrote:
> Sourbh reported an oops that is triggerable by trying to read the
> pool_stats procfile before nfsd had been started. Move the check for a
> NULL serv in svc_pool_stats_start above the mutex acquisition, and fix
> the stop routine not to unlock the mutex if there is no serv yet.
> 
> Fixes: 7b207ccd9833 ("svc: don't hold reference for poolstats, only mutex.")
> Reported-by: Sourabh Jain <sourabhjain@...ux.ibm.com>
> Signed-off-by: Jeff Layton <jlayton@...nel.org>

Applied to nfsd-fixes (for 6.10-rc). Thanks!


> ---
>  net/sunrpc/svc_xprt.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/net/sunrpc/svc_xprt.c b/net/sunrpc/svc_xprt.c
> index d3735ab3e6d1..b757a8891813 100644
> --- a/net/sunrpc/svc_xprt.c
> +++ b/net/sunrpc/svc_xprt.c
> @@ -1422,12 +1422,13 @@ static void *svc_pool_stats_start(struct seq_file *m, loff_t *pos)
>  
>  	dprintk("svc_pool_stats_start, *pidx=%u\n", pidx);
>  
> +	if (!si->serv)
> +		return NULL;
> +
>  	mutex_lock(si->mutex);
>  
>  	if (!pidx)
>  		return SEQ_START_TOKEN;
> -	if (!si->serv)
> -		return NULL;
>  	return pidx > si->serv->sv_nrpools ? NULL
>  		: &si->serv->sv_pools[pidx - 1];
>  }
> @@ -1459,7 +1460,8 @@ static void svc_pool_stats_stop(struct seq_file *m, void *p)
>  {
>  	struct svc_info *si = m->private;
>  
> -	mutex_unlock(si->mutex);
> +	if (si->serv)
> +		mutex_unlock(si->mutex);
>  }
>  
>  static int svc_pool_stats_show(struct seq_file *m, void *p)
> 
> ---
> base-commit: 4ddfda417a50309f17aeb85f8d1a9a9efbc7d81c
> change-id: 20240617-nfsd-next-8593f73544f5
> 
> Best regards,
> -- 
> Jeff Layton <jlayton@...nel.org>
> 

-- 
Chuck Lever