[026/145] vfs: take f_lock on modifying f_mode after open time

[Greg KH]

2.6.32-stable review patch.  If anyone has any objections, please let me know.

----------------
From: Wu Fengguang <fengguang.wu@xxxxxxxxx>

commit 42e49608683ab25fbbbf9c40edb944601e543882 upstream.

We'll introduce FMODE_RANDOM which will be runtime modified.  So protect
all runtime modification to f_mode with f_lock to avoid races.

Signed-off-by: Wu Fengguang <fengguang.wu@xxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Cc: Trond Myklebust <Trond.Myklebust@xxxxxxxxxx>
Cc: Chuck Lever <chuck.lever@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

---
 fs/file_table.c     |    2 ++
 fs/nfsd/nfs4state.c |    2 ++
 2 files changed, 4 insertions(+)

--- a/fs/file_table.c
+++ b/fs/file_table.c
@@ -420,7 +420,9 @@ retry:
 			continue;
 		if (!(f->f_mode & FMODE_WRITE))
 			continue;
+		spin_lock(&f->f_lock);
 		f->f_mode &= ~FMODE_WRITE;
+		spin_unlock(&f->f_lock);
 		if (file_check_writeable(f) != 0)
 			continue;
 		file_release_write(f);
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -2002,7 +2002,9 @@ nfs4_file_downgrade(struct file *filp, u
 {
 	if (share_access & NFS4_SHARE_ACCESS_WRITE) {
 		drop_file_write_access(filp);
+		spin_lock(&filp->f_lock);
 		filp->f_mode = (filp->f_mode | FMODE_READ) & ~FMODE_WRITE;
+		spin_unlock(&filp->f_lock);
 	}
 }
 


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