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.
Fixes: 93483ac5fec6 ("nfsd: expose /proc/net/sunrpc/nfsd in net namespaces")
Reported-by: syzbot+e34ad04f27991521104c@xxxxxxxxxxxxxxxxxxxxxxxxx
Closes: https://lore.kernel.org/linux-nfs/67a47501.050a0220.19061f.05f9.GAE@xxxxxxxxxx/
Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx>
---
I looked at the console log from the report, and syzkaller is doing
fault injection on allocations. You can see the stack where the "nfsd"
directory under /proc failed to be created due to one. This is a pretty
unlikely bug under normal circumstances, but it's simple to fix. The
problem predates the patch in Fixes:, but it's not worth the effort to
backport this to anything earlier.
---
fs/nfsd/nfsctl.c | 9 ++++++++-
fs/nfsd/stats.c | 4 ++--
fs/nfsd/stats.h | 2 +-
3 files changed, 11 insertions(+), 4 deletions(-)
diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c
index 95ea4393305bd38493b640fbaba2e8f57f5a501d..583eda0df54dca394de4bbe8d148be2892df39cb 100644
--- a/fs/nfsd/nfsctl.c
+++ b/fs/nfsd/nfsctl.c
@@ -2204,8 +2204,14 @@ 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++)
@@ -2215,12 +2221,13 @@ 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:
diff --git a/fs/nfsd/stats.c b/fs/nfsd/stats.c
index bb22893f1157e4c159e123b6d8e25b8eab52e187..f7eaf95e20fc8758566f469c6c2de79119fea070 100644
--- a/fs/nfsd/stats.c
+++ b/fs/nfsd/stats.c
@@ -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)
diff --git a/fs/nfsd/stats.h b/fs/nfsd/stats.h
index 04aacb6c36e2576ba231ee481e3a3e9e9f255a61..e4efb0e4e56d467c13eaa5a1dd312c85dadeb4b8 100644
--- a/fs/nfsd/stats.h
+++ b/fs/nfsd/stats.h
@@ -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)
---
base-commit: ebbdc9429c39336a406b191cfe84bca2c12c2f73
change-id: 20250206-nfsd-fixes-8e61bdf66347
Best regards,
--
Jeff Layton <jlayton@xxxxxxxxxx>
