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Prevent memory leak in devpts

PATCH In review Olaf Kirch 1 participant 2 messages Aug 25, 2004

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Olaf Kirch

author
#0 lore raw

PATCH 1/1 Prevent memory leak in devpts

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

Signature · 3 lines
Olaf Kirch     |  The Hardware Gods hate me.
[email protected]   |
---------------+
fs/devpts/inode.c +1 -0
Index: 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;
 }
author
#1 lore raw

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

Signature · 3 lines
Olaf Kirch     |  The Hardware Gods hate me.
[email protected]   |
---------------+
fs/devpts/inode.c +7 -3
Index: 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);