linux-kernel - [026/145] vfs: take f_lock on modifying f

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Message-Id: <20100313002707.516438708@kvm.kroah.org>
Date:	Fri, 12 Mar 2010 16:25:59 -0800
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...nel.org
Cc:	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Wu Fengguang <fengguang.wu@...el.com>,
	Al Viro <viro@...iv.linux.org.uk>,
	Christoph Hellwig <hch@...radead.org>,
	Trond Myklebust <Trond.Myklebust@...app.com>,
	Chuck Lever <chuck.lever@...cle.com>
Subject: [026/145] vfs: take f_lock on modifying f_mode after open time

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

----------------
From: Wu Fengguang <fengguang.wu@...el.com>

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@...el.com>
Cc: Al Viro <viro@...iv.linux.org.uk>
Cc: Christoph Hellwig <hch@...radead.org>
Cc: Trond Myklebust <Trond.Myklebust@...app.com>
Cc: Chuck Lever <chuck.lever@...cle.com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

---
 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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