devpts: plug the memory leak in kill_sb

Ilija Hadzic · torvalds · commit 66da0e1f9034 · 2013-11-13T12:09:36.000+09:00
When devpts is unmounted, there may be a no-longer-used IDR tree hanging
off the superblock we are about to kill.  This needs to be cleaned up
before destroying the SB.

The leak is usually not a big deal because unmounting devpts is typically
done when shutting down the whole machine.  However, shutting down an LXC
container instead of a physical machine exposes the problem (the garbage
is detectable with kmemleak).

Signed-off-by: Ilija Hadzic &lt;ihadzic@research.bell-labs.com&gt;
Cc: Sukadev Bhattiprolu &lt;sukadev@linux.vnet.ibm.com&gt;
Cc: &lt;stable@vger.kernel.org&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
diff --git a/fs/devpts/inode.c b/fs/devpts/inode.c
@@ -498,6 +498,7 @@ static void devpts_kill_sb(struct super_block *sb)
 {
 	struct pts_fs_info *fsi = DEVPTS_SB(sb);
 
+	ida_destroy(&fsi->allocated_ptys);
 	kfree(fsi);
 	kill_litter_super(sb);
 }

Original file line number	Diff line number	Diff line change
`@@ -498,6 +498,7 @@ static void devpts_kill_sb(struct super_block *sb)`
`498`	`498`	`{`
`499`	`499`	`struct pts_fs_info *fsi = DEVPTS_SB(sb);`
`500`	`500`
	`501`	`+ ida_destroy(&fsi->allocated_ptys);`
`501`	`502`	`kfree(fsi);`
`502`	`503`	`kill_litter_super(sb);`
`503`	`504`	`}`