linux-kernel - [PATCH] NFSv4.2: fix reference count leaks in _nfs42_proc_copy

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Date:   Tue, 25 Jan 2022 21:10:45 +0800
From:   Xin Xiong <xiongx18@...an.edu.cn>
To:     Trond Myklebust <trond.myklebust@...merspace.com>,
        Anna Schumaker <anna.schumaker@...app.com>,
        linux-nfs@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     yuanxzhang@...an.edu.cn, Xin Xiong <xiongx18@...an.edu.cn>,
        Xiyu Yang <xiyuyang19@...an.edu.cn>,
        Xin Tan <tanxin.ctf@...il.com>
Subject: [PATCH] NFSv4.2: fix reference count leaks in _nfs42_proc_copy_notify()

The reference counting issue happens in two error paths in the
function _nfs42_proc_copy_notify(). In both error paths, the function
simply returns the error code and forgets to balance the refcount of
object `ctx`, bumped by get_nfs_open_context() earlier, which may
cause refcount leaks.

Fix it by balancing refcount of the `ctx` object before the function
returns in both error paths.

Signed-off-by: Xin Xiong <xiongx18@...an.edu.cn>
Signed-off-by: Xiyu Yang <xiyuyang19@...an.edu.cn>
Signed-off-by: Xin Tan <tanxin.ctf@...il.com>
---
 fs/nfs/nfs42proc.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/fs/nfs/nfs42proc.c b/fs/nfs/nfs42proc.c
index 8b21ff1be..438de4f93 100644
--- a/fs/nfs/nfs42proc.c
+++ b/fs/nfs/nfs42proc.c
@@ -592,8 +592,10 @@ static int _nfs42_proc_copy_notify(struct file *src, struct file *dst,
 
 	ctx = get_nfs_open_context(nfs_file_open_context(src));
 	l_ctx = nfs_get_lock_context(ctx);
-	if (IS_ERR(l_ctx))
-		return PTR_ERR(l_ctx);
+	if (IS_ERR(l_ctx)) {
+		status = PTR_ERR(l_ctx);
+		goto out;
+	}
 
 	status = nfs4_set_rw_stateid(&args->cna_src_stateid, ctx, l_ctx,
 				     FMODE_READ);
@@ -601,7 +603,7 @@ static int _nfs42_proc_copy_notify(struct file *src, struct file *dst,
 	if (status) {
 		if (status == -EAGAIN)
 			status = -NFS4ERR_BAD_STATEID;
-		return status;
+		goto out;
 	}
 
 	status = nfs4_call_sync(src_server->client, src_server, &msg,
@@ -610,6 +612,7 @@ static int _nfs42_proc_copy_notify(struct file *src, struct file *dst,
 	if (status == -ENOTSUPP)
 		src_server->caps &= ~NFS_CAP_COPY_NOTIFY;
 
+out:
 	put_nfs_open_context(nfs_file_open_context(src));
 	return status;
 }
-- 
2.25.1