Re: local denial-of-service with file leases

[Chris Wright <chrisw@osdl.org>]

* Avi Kivity (avi@argo.co.il) wrote:
> the following program will oom a the 2.6.14.1 kernel, running as an 
> ordinary user:

I don't have a good mechanism for testing leases, but this should fix
the leak.  Mind testing?

thanks,
-chris
--

When unlocking lease make sure to release fasync_struct.

Signed-off-by: Chris Wright <chrisw@osdl.org>
---

diff --git a/fs/locks.c b/fs/locks.c
index a1e8b22..abba0f6 100644
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -1412,7 +1412,7 @@ int fcntl_setlease(unsigned int fd, stru
 	struct file_lock fl, *flp = &fl;
 	struct dentry *dentry = filp->f_dentry;
 	struct inode *inode = dentry->d_inode;
-	int error;
+	int error, on = 1;
 
 	if ((current->fsuid != inode->i_uid) && !capable(CAP_LEASE))
 		return -EACCES;
@@ -1433,7 +1433,10 @@ int fcntl_setlease(unsigned int fd, stru
 	if (error)
 		goto out_unlock;
 
-	error = fasync_helper(fd, filp, 1, &flp->fl_fasync);
+	if (arg == F_UNLCK)
+		on = 0;
+
+	error = fasync_helper(fd, filp, on, &flp->fl_fasync);
 	if (error < 0) {
 		/* remove lease just inserted by __setlease */
 		flp->fl_type = F_UNLCK | F_INPROGRESS;