Patch "x86/intel_rdt: Put group node in rdtgroup_kn_unlock" has been added to the 4.10-stable tree

This is a note to let you know that I've just added the patch titled

x86/intel_rdt: Put group node in rdtgroup_kn_unlock

to the 4.10-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
x86-intel_rdt-put-group-node-in-rdtgroup_kn_unlock.patch
and it can be found in the queue-4.10 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Jiri Olsa <[email protected]>
Date: Tue, 14 Mar 2017 15:20:53 +0100
Subject: x86/intel_rdt: Put group node in rdtgroup_kn_unlock

From: Jiri Olsa <[email protected]>

commit 49ec8f5b6ae3ab60385492cad900ffc8a523c895 upstream.

The rdtgroup_kn_unlock waits for the last user to release and put its node. But it's calling kernfs_put on the node which calls the rdtgroup_kn_unlock, which might not be the group's directory node, but another group's file node.

This race could be easily reproduced by running 2 instances of following script:

mount -t resctrl resctrl /sys/fs/resctrl/
pushd /sys/fs/resctrl/
mkdir krava
echo "krava" > krava/schemata
rmdir krava
popd
umount /sys/fs/resctrl

It triggers the slub debug error message with following command line config: slub_debug=,kernfs_node_cache.

Call kernfs_put on the group's node to fix it.

---
 arch/x86/kernel/cpu/intel_rdt_rdtgroup.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

@@ -727,7 +727,7 @@ void rdtgroup_kn_unlock(struct kernfs_no
 	if (atomic_dec_and_test(&rdtgrp->waitcount) &&
 	    (rdtgrp->flags & RDT_DELETED)) {
 		kernfs_unbreak_active_protection(kn);
-		kernfs_put(kn);
+		kernfs_put(rdtgrp->kn);
 		kfree(rdtgrp);
 	} else {
 		kernfs_unbreak_active_protection(kn);

Patches currently in stable-queue which might be from [email protected] are

queue-4.10/x86-intel_rdt-put-group-node-in-rdtgroup_kn_unlock.patch