From f3c7691e8d30d88899b514675c7c86d19057b5fd Mon Sep 17 00:00:00 2001
From: "J. Bruce Fields" <bfields@redhat.com>
Date: Wed, 21 Sep 2011 10:58:13 -0400
Subject: [PATCH] leases: fix write-open/read-lease race
In setlease, we use i_writecount to decide whether we can give out a
read lease.
In open, we break leases before incrementing i_writecount.
There is therefore a window between the break lease and the i_writecount
increment when setlease could add a new read lease.
This would leave us with a simultaneous write open and read lease, which
shouldn't happen.
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
---
fs/namei.c | 5 +----
fs/open.c | 4 ++++
2 files changed, 5 insertions(+), 4 deletions(-)
diff --git a/fs/namei.c b/fs/namei.c
index 9061157e39d6e7..7657be4352bf64 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -2035,10 +2035,7 @@ static int may_open(struct path *path, int acc_mode, int flag)
if (flag & O_NOATIME && !inode_owner_or_capable(inode))
return -EPERM;
- /*
- * Ensure there are no outstanding leases on the file.
- */
- return break_lease(inode, flag);
+ return 0;
}
static int handle_truncate(struct file *filp)
diff --git a/fs/open.c b/fs/open.c
index f711921094576c..22c41b543f2dfc 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -685,6 +685,10 @@ static struct file *__dentry_open(struct dentry *dentry, struct vfsmount *mnt,
if (error)
goto cleanup_all;
+ error = break_lease(inode, f->f_flags);
+ if (error)
+ goto cleanup_all;
+
if (!open && f->f_op)
open = f->f_op->open;
if (open) {
--
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