nfsd: don't ignore the return code of svc_proc_register()

From: Jeff Layton <[email protected]>

[ Upstream commit 930b64ca0c511521f0abdd1d57ce52b2a6e3476b ]

Currently, nfsd_proc_stat_init() ignores the return value of svc_proc_register(). If the procfile creation fails, then the kernel will WARN when it tries to remove the entry later.

Fix nfsd_proc_stat_init() to return the same type of pointer as svc_proc_register(), and fix up nfsd_net_init() to check that and fail the nfsd_net construction if it occurs.

svc_proc_register() can fail if the dentry can't be allocated, or if an identical dentry already exists. The second case is pretty unlikely in the nfsd_net construction codepath, so if this happens, return -ENOMEM.

---
 fs/nfsd/nfsctl.c | 9 ++++++++-
 fs/nfsd/stats.c  | 4 ++--
 fs/nfsd/stats.h  | 2 +-
 3 files changed, 11 insertions(+), 4 deletions(-)

I did not have any problem cherry-picking 930b64 onto v6.13.11. This built and ran some simple NFSD tests in my lab.

index e83629f39604..2e835e7c107e 100644
@@ -2244,8 +2244,14 @@ static __net_init int nfsd_net_init(struct net *net)
 					  NFSD_STATS_COUNTERS_NUM);
 	if (retval)
 		goto out_repcache_error;
+
 	memset(&nn->nfsd_svcstats, 0, sizeof(nn->nfsd_svcstats));
 	nn->nfsd_svcstats.program = &nfsd_programs[0];
+	if (!nfsd_proc_stat_init(net)) {
+		retval = -ENOMEM;
+		goto out_proc_error;
+	}
+
 	for (i = 0; i < sizeof(nn->nfsd_versions); i++)
 		nn->nfsd_versions[i] = nfsd_support_version(i);
 	for (i = 0; i < sizeof(nn->nfsd4_minorversions); i++)

@@ -2255,12 +2261,13 @@ static __net_init int nfsd_net_init(struct net *net)
 	nfsd4_init_leases_net(nn);
 	get_random_bytes(&nn->siphash_key, sizeof(nn->siphash_key));
 	seqlock_init(&nn->writeverf_lock);
-	nfsd_proc_stat_init(net);
 #if IS_ENABLED(CONFIG_NFS_LOCALIO)
 	INIT_LIST_HEAD(&nn->local_clients);
 #endif
 	return 0;
 
+out_proc_error:
+	percpu_counter_destroy_many(nn->counter, NFSD_STATS_COUNTERS_NUM);
 out_repcache_error:
 	nfsd_idmap_shutdown(net);
 out_idmap_error:

index bb22893f1157..f7eaf95e20fc 100644
@@ -73,11 +73,11 @@ static int nfsd_show(struct seq_file *seq, void *v)
 
 DEFINE_PROC_SHOW_ATTRIBUTE(nfsd);
 
-void nfsd_proc_stat_init(struct net *net)
+struct proc_dir_entry *nfsd_proc_stat_init(struct net *net)
 {
 	struct nfsd_net *nn = net_generic(net, nfsd_net_id);
 
-	svc_proc_register(net, &nn->nfsd_svcstats, &nfsd_proc_ops);
+	return svc_proc_register(net, &nn->nfsd_svcstats, &nfsd_proc_ops);
 }
 
 void nfsd_proc_stat_shutdown(struct net *net)

index 04aacb6c36e2..e4efb0e4e56d 100644
@@ -10,7 +10,7 @@
 #include <uapi/linux/nfsd/stats.h>
 #include <linux/percpu_counter.h>
 
-void nfsd_proc_stat_init(struct net *net);
+struct proc_dir_entry *nfsd_proc_stat_init(struct net *net);
 void nfsd_proc_stat_shutdown(struct net *net);
 
 static inline void nfsd_stats_rc_hits_inc(struct nfsd_net *nn)

2.47.0

[ Sasha's backport helper bot ]

Hi,

✅ All tests passed successfully. No issues detected. No action required from the submitter.

The upstream commit SHA1 provided is correct: 930b64ca0c511521f0abdd1d57ce52b2a6e3476b

WARNING: Author mismatch between patch and upstream commit:
Backport author: [email protected]
Commit author: Jeff Layton<[email protected]>

Status in newer kernel trees:
6.14.y | Present (different SHA1: 9d9456185fd5)

Note: The patch differs from the upstream commit:
---
1: 930b64ca0c511 ! 1: 23c220e9285a7 nfsd: don't ignore the return code of svc_proc_register()
@@ Metadata
## Commit message ##
nfsd: don't ignore the return code of svc_proc_register()

+ [ Upstream commit 930b64ca0c511521f0abdd1d57ce52b2a6e3476b ]
+
Currently, nfsd_proc_stat_init() ignores the return value of svc_proc_register(). If the procfile creation fails, then the kernel will WARN when it tries to remove the entry later.
@@ fs/nfsd/nfsctl.c: static __net_init int nfsd_net_init(struct net *net)
seqlock_init(&nn->writeverf_lock);
- nfsd_proc_stat_init(net);
#if IS_ENABLED(CONFIG_NFS_LOCALIO)
- spin_lock_init(&nn->local_clients_lock);
INIT_LIST_HEAD(&nn->local_clients);
#endif
return 0;
---

Results of testing on various branches:

| Branch                    | Patch Apply | Build Test |
|---------------------------|-------------|------------|
| stable/linux-6.13.y       |  Success    |  Success   |