Forwarded: [PATCH] nfsd: fix memory leak in nfsd_create_serv error paths

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Subject: [PATCH] nfsd: fix memory leak in nfsd_create_serv error paths
Author: kartikey406@gmail.com

#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master

When svc_create_pooled() or svc_bind() fails, nfsd_create_serv() returns
an error without calling percpu_ref_exit() to clean up the percpu
reference that was initialized earlier in the function.

This causes two memory leaks per failed call:
  - 8 bytes of percpu memory (the reference counter)
  - 64 bytes of slab memory (the percpu_ref_data structure)

Fix this by adding an error label that calls percpu_ref_exit() before
returning.

Reported-by: syzbot+6ee3b889bdeada0a6226@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=6ee3b889bdeada0a6226
Signed-off-by: Deepanshu Kartikey <kartikey406@gmail.com>
---
 fs/nfsd/nfssvc.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/fs/nfsd/nfssvc.c b/fs/nfsd/nfssvc.c
index b08ae85d53ef..49fd77c8f98d 100644
--- a/fs/nfsd/nfssvc.c
+++ b/fs/nfsd/nfssvc.c
@@ -615,13 +615,14 @@ int nfsd_create_serv(struct net *net)
 	serv = svc_create_pooled(nfsd_programs, ARRAY_SIZE(nfsd_programs),
 				 &nn->nfsd_svcstats,
 				 nfsd_max_blksize, nfsd);
-	if (serv == NULL)
-		return -ENOMEM;
-
+	if (serv == NULL) {
+		error = -ENOMEM;
+		goto err_percpu;
+	}
 	error = svc_bind(serv, net);
 	if (error < 0) {
 		svc_destroy(&serv);
-		return error;
+		goto err_percpu;
 	}
 	spin_lock(&nfsd_notifier_lock);
 	nn->nfsd_serv = serv;
@@ -636,6 +637,9 @@ int nfsd_create_serv(struct net *net)
 	}
 	nfsd_reset_write_verifier(nn);
 	return 0;
+err_percpu:
+	percpu_ref_exit(&nn->nfsd_net_ref);
+	return error;
 }
 
 int nfsd_nrpools(struct net *net)
-- 
2.43.0