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

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Hello Jeff,

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

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@xxxxxxxxxxxxx>
Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx>
---
  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,





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