2019-06-10 17:17:31

by Prarit Bhargava

Subject: [PATCH] x86/resctrl: Fix panic on systems that do not enable local MBM

Booting with kernel parameter "rdt=cmt,mbmtotal,memlocal,l3cat,mba" and
executing "mount -t resctrl resctrl -o mba_MBps /sys/fs/resctrl"
results in a panic on systems without local MBM support enabled in
firmware.

BUG: kernel NULL pointer dereference, address: 0000000000000020
PGD 0 P4D 0
Oops: 0000 [#1] SMP PTI
CPU: 0 PID: 722 Comm: kworker/0:3 Not tainted 5.2.0-0.rc3.git0.1.el7_UNSUPPORTED.x86_64 #2
Hardware name: Dell Inc. PowerEdge R740/0923K0, BIOS 2.1.8 04/30/2019
Workqueue: events mbm_handle_overflow
RIP: 0010:mbm_handle_overflow+0x150/0x2b0

Only call the bandwith update loop if the system has local MBM enabled.

Signed-off-by: Prarit Bhargava <[email protected]>
Cc: Fenghua Yu <[email protected]>
Cc: Reinette Chatre <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: [email protected]
---
arch/x86/kernel/cpu/resctrl/monitor.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/arch/x86/kernel/cpu/resctrl/monitor.c b/arch/x86/kernel/cpu/resctrl/monitor.c
index 7ee93125a211..397206f23d14 100644
--- a/arch/x86/kernel/cpu/resctrl/monitor.c
+++ b/arch/x86/kernel/cpu/resctrl/monitor.c
@@ -360,6 +360,9 @@ static void update_mba_bw(struct rdtgroup *rgrp, struct rdt_domain *dom_mbm)
struct list_head *head;
struct rdtgroup *entry;

+ if (!is_mbm_local_enabled())
+ return;
+
r_mba = &rdt_resources_all[RDT_RESOURCE_MBA];
closid = rgrp->closid;
rmid = rgrp->mon.rmid;
--
2.21.0

2019-06-12 17:18:54

by tip-bot for Vasyl Gomonovych

Subject: [tip:x86/urgent] x86/resctrl: Prevent NULL pointer dereference when local MBM is disabled

Commit-ID: c7563e62a6d720aa3b068e26ddffab5f0df29263
Gitweb: https://git.kernel.org/tip/c7563e62a6d720aa3b068e26ddffab5f0df29263
Author: Prarit Bhargava <[email protected]>
AuthorDate: Mon, 10 Jun 2019 13:15:44 -0400
Committer: Thomas Gleixner <[email protected]>
CommitDate: Wed, 12 Jun 2019 10:31:50 +0200

x86/resctrl: Prevent NULL pointer dereference when local MBM is disabled

Booting with kernel parameter "rdt=cmt,mbmtotal,memlocal,l3cat,mba" and
executing "mount -t resctrl resctrl -o mba_MBps /sys/fs/resctrl" results in
a NULL pointer dereference on systems which do not have local MBM support
enabled..

BUG: kernel NULL pointer dereference, address: 0000000000000020
PGD 0 P4D 0
Oops: 0000 [#1] SMP PTI
CPU: 0 PID: 722 Comm: kworker/0:3 Not tainted 5.2.0-0.rc3.git0.1.el7_UNSUPPORTED.x86_64 #2
Workqueue: events mbm_handle_overflow
RIP: 0010:mbm_handle_overflow+0x150/0x2b0

Only enter the bandwith update loop if the system has local MBM enabled.

Fixes: de73f38f7680 ("x86/intel_rdt/mba_sc: Feedback loop to dynamically update mem bandwidth")
Signed-off-by: Prarit Bhargava <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Cc: Fenghua Yu <[email protected]>
Cc: Reinette Chatre <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: [email protected]
Link: https://lkml.kernel.org/r/[email protected]

---
arch/x86/kernel/cpu/resctrl/monitor.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/arch/x86/kernel/cpu/resctrl/monitor.c b/arch/x86/kernel/cpu/resctrl/monitor.c
index 1573a0a6b525..ff6e8e561405 100644
--- a/arch/x86/kernel/cpu/resctrl/monitor.c
+++ b/arch/x86/kernel/cpu/resctrl/monitor.c
@@ -368,6 +368,9 @@ static void update_mba_bw(struct rdtgroup *rgrp, struct rdt_domain *dom_mbm)
struct list_head *head;
struct rdtgroup *entry;

+ if (!is_mbm_local_enabled())
+ return;
+
r_mba = &rdt_resources_all[RDT_RESOURCE_MBA];
closid = rgrp->closid;
rmid = rgrp->mon.rmid;