[tip:x86/urgent] x86/intel_rdt: Fix locking in rdtgroup_schemata_write()

[tip-bot for Jiri Olsa]

Commit-ID:  7f00f388712b29005782bad7e4b25942620f3b9c
Gitweb:     http://git.kernel.org/tip/7f00f388712b29005782bad7e4b25942620f3b9c
Author:     Jiri Olsa <jolsa@xxxxxxxxxx>
AuthorDate: Tue, 11 Apr 2017 09:14:46 +0200
Committer:  Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitDate: Tue, 11 Apr 2017 09:48:12 +0200

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@xxxxxxxxxx>
Cc: Fenghua Yu <fenghua.yu@xxxxxxxxx>
Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Mike Galbraith <efault@xxxxxx>
Cc: Shaohua Li <shli@xxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Link: http://lkml.kernel.org/r/20170411071446.15241-1-jolsa@xxxxxxxxxx
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
---
 arch/x86/kernel/cpu/intel_rdt_schemata.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/intel_rdt_schemata.c b/arch/x86/kernel/cpu/intel_rdt_schemata.c
index f369cb8..badd2b3 100644
--- 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;
 }