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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Lyu Tao <tao.lyu@epfl.ch>,
        ChenXiaoSong <chenxiaosong2@huawei.com>,
        Trond Myklebust <trond.myklebust@hammerspace.com>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.16 154/285] Revert "NFSv4: Handle the special Linux file open access mode"
Date:   Tue, 12 Apr 2022 08:30:11 +0200
Message-Id: <20220412062948.117828131@linuxfoundation.org>
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From: ChenXiaoSong <chenxiaosong2@huawei.com>

[ Upstream commit ab0fc21bc7105b54bafd85bd8b82742f9e68898a ]

This reverts commit 44942b4e457beda00981f616402a1a791e8c616e.

After secondly opening a file with O_ACCMODE|O_DIRECT flags,
nfs4_valid_open_stateid() will dereference NULL nfs4_state when lseek().

Reproducer:
  1. mount -t nfs -o vers=4.2 $server_ip:/ /mnt/
  2. fd = open("/mnt/file", O_ACCMODE|O_DIRECT|O_CREAT)
  3. close(fd)
  4. fd = open("/mnt/file", O_ACCMODE|O_DIRECT)
  5. lseek(fd)

Reported-by: Lyu Tao <tao.lyu@epfl.ch>
Signed-off-by: ChenXiaoSong <chenxiaosong2@huawei.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/nfs/inode.c    | 1 -
 fs/nfs/nfs4file.c | 2 +-
 2 files changed, 1 insertion(+), 2 deletions(-)

diff --git a/fs/nfs/inode.c b/fs/nfs/inode.c
index a09d3ff627c2..4da8a4a7bad7 100644
--- a/fs/nfs/inode.c
+++ b/fs/nfs/inode.c
@@ -1180,7 +1180,6 @@ int nfs_open(struct inode *inode, struct file *filp)
 	nfs_fscache_open_file(inode, filp);
 	return 0;
 }
-EXPORT_SYMBOL_GPL(nfs_open);
 
 /*
  * This function is called whenever some part of NFS notices that
diff --git a/fs/nfs/nfs4file.c b/fs/nfs/nfs4file.c
index e79ae4cbc395..c178db86a6e8 100644
--- a/fs/nfs/nfs4file.c
+++ b/fs/nfs/nfs4file.c
@@ -51,7 +51,7 @@ nfs4_file_open(struct inode *inode, struct file *filp)
 		return err;
 
 	if ((openflags & O_ACCMODE) == 3)
-		return nfs_open(inode, filp);
+		openflags--;
 
 	/* We can't create new files here */
 	openflags &= ~(O_CREAT|O_EXCL);
-- 
2.35.1