linux-kernel - [PATCH 4.10 24/69] x86/intel_rdt: Fix locking in rdtgroup_schemata

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Message-Id: <20170419141556.129312607@linuxfoundation.org>
Date:   Wed, 19 Apr 2017 16:36:53 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Jiri Olsa <jolsa@...nel.org>,
        Fenghua Yu <fenghua.yu@...el.com>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Peter Zijlstra <peterz@...radead.org>,
        Mike Galbraith <efault@....de>, Shaohua Li <shli@...com>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: [PATCH 4.10 24/69] x86/intel_rdt: Fix locking in rdtgroup_schemata_write()

4.10-stable review patch.  If anyone has any objections, please let me know.

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

From: Jiri Olsa <jolsa@...nel.org>

commit 7f00f388712b29005782bad7e4b25942620f3b9c upstream.

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@...nel.org>
Cc: Fenghua Yu <fenghua.yu@...el.com>
Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Mike Galbraith <efault@....de>
Cc: Shaohua Li <shli@...com>
Link: http://lkml.kernel.org/r/20170411071446.15241-1-jolsa@kernel.org
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

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

--- 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 k
 	}
 
 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;
 }