devpts: plug the memory leak in kill_sb

commit 66da0e1f9034140ae2f571ef96e254a25083906c upstream.

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 <ihadzic@research.bell-labs.com>
Cc: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/fs/devpts/inode.c b/fs/devpts/inode.c
index d5d5297efe97bd4115b2d3e8f37575e6ae054f56..2a950478a9cdc0b2c9c86df7ae04e4c7227b7397 100644 (file)
--- a/fs/devpts/inode.c
+++ b/fs/devpts/inode.c
@@ -413,6 +413,7 @@ 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);
 }