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Subject[PATCH 4.10 57/63] x86/intel_rdt: Put group node in rdtgroup_kn_unlock
Date
4.10-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Jiri Olsa <jolsa@kernel.org>

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.

Fixes: 60cf5e101fd4 ("x86/intel_rdt: Add mkdir to resctrl file system")
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Shaohua Li <shli@fb.com>
Link: http://lkml.kernel.org/r/1489501253-20248-1-git-send-email-jolsa@kernel.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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

--- a/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c
+++ b/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c
@@ -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);

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