[PATCH] nfsd: fix oops when reading pool_stats before server is started

[PATCH] nfsd: fix oops when reading pool_stats before server is started

[Jeff Layton]

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@linux.ibm.com>
Signed-off-by: Jeff Layton <jlayton@kernel.org>
---
 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@kernel.org>

Re: [PATCH] nfsd: fix oops when reading pool_stats before server is started

[Sourabh Jain]

Hello Jeff,

With the below fix applied, the issue is not observed.
Tested-by: Sourabh Jain <sourabhjain@linux.ibm.com>

Thanks for the fix.

- Sourabh Jain

On 17/06/24 17:24, 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@linux.ibm.com>
> Signed-off-by: Jeff Layton <jlayton@kernel.org>
> ---
>   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,

Re: [PATCH] nfsd: fix oops when reading pool_stats before server is started

[Chuck Lever]

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@linux.ibm.com>
> Signed-off-by: Jeff Layton <jlayton@kernel.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@kernel.org>
> 

-- 
Chuck Lever