linux-kernel - [tip:x86/urgent] x86/intel_rdt: Fix locking in rdtgroup_schemata

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Message-ID: <tip-7f00f388712b29005782bad7e4b25942620f3b9c@git.kernel.org>
Date:   Tue, 11 Apr 2017 01:03:46 -0700
From:   tip-bot for Jiri Olsa <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     tglx@...utronix.de, shli@...com, hpa@...or.com, mingo@...nel.org,
        peterz@...radead.org, jolsa@...nel.org, fenghua.yu@...el.com,
        linux-kernel@...r.kernel.org, efault@....de, a.p.zijlstra@...llo.nl
Subject: [tip:x86/urgent] x86/intel_rdt: Fix locking in
 rdtgroup_schemata_write()

Commit-ID:  7f00f388712b29005782bad7e4b25942620f3b9c
Gitweb:     http://git.kernel.org/tip/7f00f388712b29005782bad7e4b25942620f3b9c
Author:     Jiri Olsa <jolsa@...nel.org>
AuthorDate: Tue, 11 Apr 2017 09:14:46 +0200
Committer:  Thomas Gleixner <tglx@...utronix.de>
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@...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>
Cc: stable@...r.kernel.org
Link: http://lkml.kernel.org/r/20170411071446.15241-1-jolsa@kernel.org
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
---
 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;
 }