[PATCH] Prevent memory leak in devpts

[PATCH] Prevent memory leak in devpts

[Olaf Kirch]

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Hi,

There is a dentry refcount leak in devpts_get_tty.

struct tty_struct *devpts_get_tty(int number)
{
        struct dentry *dentry = get_node(number);
        struct tty_struct *tty;

        tty = (IS_ERR(dentry) || !dentry->d_inode) ? NULL :
                        dentry->d_inode->u.generic_ip;

        up(&devpts_root->d_inode->i_sem);
        return tty;
}

The get_node function does a lookup on /dev/pts/<number> and returns the
dentry, taking a reference. We should dput the dentry after extracting
the tty pointer.

The attached patch does this.

Olaf
-- 
Olaf Kirch     |  The Hardware Gods hate me.
okir@suse.de   |
---------------+ 

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Index: v268/fs/devpts/inode.c
===================================================================
--- v268.orig/fs/devpts/inode.c
+++ v268/fs/devpts/inode.c
@@ -183,6 +183,7 @@ struct tty_struct *devpts_get_tty(int nu
 			dentry->d_inode->u.generic_ip;
 
 	up(&devpts_root->d_inode->i_sem);
+	dput(dentry);
 
 	return tty;
 }

Re: [PATCH] Prevent memory leak in devpts

[Olaf Kirch]

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This is a lame self-followup. Kurt Garloff pointed out that I should
obviously handle the error case more gracefully than by oopsing.
Improved patch attached.

Olaf
-- 
Olaf Kirch     |  The Hardware Gods hate me.
okir@suse.de   |
---------------+ 

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Index: linux-2.6.5/fs/devpts/inode.c
===================================================================
--- linux-2.6.5.orig/fs/devpts/inode.c
+++ linux-2.6.5/fs/devpts/inode.c
@@ -178,9 +178,13 @@ struct tty_struct *devpts_get_tty(int nu
 {
 	struct dentry *dentry = get_node(number);
 	struct tty_struct *tty;
-
-	tty = (IS_ERR(dentry) || !dentry->d_inode) ? NULL :
-			dentry->d_inode->u.generic_ip;
+	
+	tty = NULL;
+	if (!IS_ERR(dentry)) {
+		if (dentry->d_inode)
+			tty = dentry->d_inode->u.generic_ip;
+		dput(dentry);
+	}
 
 	up(&devpts_root->d_inode->i_sem);