[PATCH 5.16 154/285] Revert "NFSv4: Handle the special Linux file open access mode"

Greg Kroah-Hartman
2022-04-12T08:37:58Z

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