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

From: Greg KH
Date: Fri Mar 12 2010 - 20:10:30 EST


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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