x86/intel_rdt: Fix locking in rdtgroup_schemata_write()

The schemata lock is released before freeing the resource's temporary
tmp_cbms allocation. That's racy versus another write which allocates and
uses new temporary storage, resulting in memory leaks, freeing in use
memory, double a free or any combination of those.

Move the unlock after the release code.

Fixes: 60ec2440c63d ("x86/intel_rdt: Add schemata file")
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>
Cc: stable@vger.kernel.org
Link: http://lkml.kernel.org/r/20170411071446.15241-1-jolsa@kernel.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

diff --git a/arch/x86/kernel/cpu/intel_rdt_schemata.c b/arch/x86/kernel/cpu/intel_rdt_schemata.c
index f369cb8db0d5b4332125745dd5a587148f109597..badd2b31a5605f3df24dd250d1f08c9df022b7b2 100644 (file)
--- a/arch/x86/kernel/cpu/intel_rdt_schemata.c
+++ b/arch/x86/kernel/cpu/intel_rdt_schemata.c
@@ -200,11 +200,11 @@ ssize_t rdtgroup_schemata_write(struct kernfs_open_file *of,
        }
 
 out:
-       rdtgroup_kn_unlock(of->kn);
        for_each_enabled_rdt_resource(r) {
                kfree(r->tmp_cbms);
                r->tmp_cbms = NULL;
        }
+       rdtgroup_kn_unlock(of->kn);
        return ret ?: nbytes;
 }