linux-kernel - [tip:x86/urgent] x86/intel_rdt/cqm: Prevent use after free

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Message-ID: <tip-d47924417319e3b6a728c0b690f183e75bc2a702@git.kernel.org>
Date:   Wed, 17 Jan 2018 03:00:53 -0800
From:   tip-bot for Thomas Gleixner <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     joseph.salisbury@...onical.com, rod.smith@...onical.com,
        mingo@...nel.org, eranian@...gle.com, peterz@...radead.org,
        hpa@...or.com, ak@...ux.intel.com, tony.luck@...el.com,
        vikas.shivappa@...ux.intel.com, ravi.v.shankar@...el.com,
        tglx@...utronix.de, linux-kernel@...r.kernel.org,
        fenghua.yu@...el.com
Subject: [tip:x86/urgent] x86/intel_rdt/cqm: Prevent use after free

Commit-ID:  d47924417319e3b6a728c0b690f183e75bc2a702
Gitweb:     https://git.kernel.org/tip/d47924417319e3b6a728c0b690f183e75bc2a702
Author:     Thomas Gleixner <tglx@...utronix.de>
AuthorDate: Tue, 16 Jan 2018 19:59:59 +0100
Committer:  Thomas Gleixner <tglx@...utronix.de>
CommitDate: Wed, 17 Jan 2018 11:56:47 +0100

x86/intel_rdt/cqm: Prevent use after free

intel_rdt_iffline_cpu() -> domain_remove_cpu() frees memory first and then
proceeds accessing it.

 BUG: KASAN: use-after-free in find_first_bit+0x1f/0x80
 Read of size 8 at addr ffff883ff7c1e780 by task cpuhp/31/195
 find_first_bit+0x1f/0x80
 has_busy_rmid+0x47/0x70
 intel_rdt_offline_cpu+0x4b4/0x510

 Freed by task 195:
 kfree+0x94/0x1a0
 intel_rdt_offline_cpu+0x17d/0x510

Do the teardown first and then free memory.

Fixes: 24247aeeabe9 ("x86/intel_rdt/cqm: Improve limbo list processing")
Reported-by: Joseph Salisbury <joseph.salisbury@...onical.com>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Cc: Ravi Shankar <ravi.v.shankar@...el.com>
Cc: Peter Zilstra <peterz@...radead.org>
Cc: Stephane Eranian <eranian@...gle.com>
Cc: Vikas Shivappa <vikas.shivappa@...ux.intel.com>
Cc: Andi Kleen <ak@...ux.intel.com>
Cc: "Roderick W. Smith" <rod.smith@...onical.com>
Cc: 1733662@...s.launchpad.net
Cc: Fenghua Yu <fenghua.yu@...el.com>
Cc: Tony Luck <tony.luck@...el.com>
Cc: stable@...r.kernel.org
Link: https://lkml.kernel.org/r/alpine.DEB.2.20.1801161957510.2366@nanos

---
 arch/x86/kernel/cpu/intel_rdt.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kernel/cpu/intel_rdt.c b/arch/x86/kernel/cpu/intel_rdt.c
index 88dcf84..9944237 100644
--- a/arch/x86/kernel/cpu/intel_rdt.c
+++ b/arch/x86/kernel/cpu/intel_rdt.c
@@ -525,10 +525,6 @@ static void domain_remove_cpu(int cpu, struct rdt_resource *r)
 		 */
 		if (static_branch_unlikely(&rdt_mon_enable_key))
 			rmdir_mondata_subdir_allrdtgrp(r, d->id);
-		kfree(d->ctrl_val);
-		kfree(d->rmid_busy_llc);
-		kfree(d->mbm_total);
-		kfree(d->mbm_local);
 		list_del(&d->list);
 		if (is_mbm_enabled())
 			cancel_delayed_work(&d->mbm_over);
@@ -545,6 +541,10 @@ static void domain_remove_cpu(int cpu, struct rdt_resource *r)
 			cancel_delayed_work(&d->cqm_limbo);
 		}
 
+		kfree(d->ctrl_val);
+		kfree(d->rmid_busy_llc);
+		kfree(d->mbm_total);
+		kfree(d->mbm_local);
 		kfree(d);
 		return;
 	}