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Date: Wed, 27 Jul 2016 07:46:23 -0700
From: Jeff Vander Stoep <jeffv@...gle.com>
To: kernel-hardening@...ts.openwall.com
Cc: peterz@...radead.org,
mingo@...hat.com,
acme@...nel.org,
alexander.shishkin@...ux.intel.com,
linux-doc@...r.kernel.org,
linux-kernel@...r.kernel.org,
Jeff Vander Stoep <jeffv@...gle.com>
Subject: [PATCH 2/2] security, perf: Add config option to restrict perf_event_open
When CONFIG_SECURITY_PERF_EVENTS_RESTRICT=y kernel.perf_event_paranoid
sysctl will be set to 3 by default, and no unprivileged use of the
perf_event_open syscall will be permitted unless it is changed.
This new level of restriction is intended to reduce the attack
surface of the kernel. It allows for a safe default to be set on
production systems at build time while leaving a simple means for
developers to grant access.
Signed-off-by: Jeff Vander Stoep <jeffv@...gle.com>
---
Documentation/sysctl/kernel.txt | 3 ++-
kernel/events/core.c | 4 ++++
security/Kconfig | 9 +++++++++
3 files changed, 15 insertions(+), 1 deletion(-)
diff --git a/Documentation/sysctl/kernel.txt b/Documentation/sysctl/kernel.txt
index fac9798..52daff6 100644
--- a/Documentation/sysctl/kernel.txt
+++ b/Documentation/sysctl/kernel.txt
@@ -659,7 +659,8 @@ allowed to execute.
perf_event_paranoid:
Controls use of the performance events system by unprivileged
-users (without CAP_SYS_ADMIN). The default value is 2.
+users (without CAP_SYS_ADMIN). The default value is 3 if
+CONFIG_SECURITY_PERF_EVENTS_RESTRICT is set, or 2 otherwise.
-1: Allow use of (almost) all events by all users
>=0: Disallow raw tracepoint access by users without CAP_IOC_LOCK
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 52bd100..df9df87 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -355,7 +355,11 @@ static struct srcu_struct pmus_srcu;
* 2 - disallow kernel profiling for unpriv
* 3 - disallow all unpriv perf event use
*/
+#ifdef CONFIG_SECURITY_PERF_EVENTS_RESTRICT
+int sysctl_perf_event_paranoid __read_mostly = 3;
+#else
int sysctl_perf_event_paranoid __read_mostly = 2;
+#endif
/* Minimum for 512 kiB + 1 user control page */
int sysctl_perf_event_mlock __read_mostly = 512 + (PAGE_SIZE / 1024); /* 'free' kiB per user */
diff --git a/security/Kconfig b/security/Kconfig
index df28f2b..2a93551 100644
--- a/security/Kconfig
+++ b/security/Kconfig
@@ -18,6 +18,15 @@ config SECURITY_DMESG_RESTRICT
If you are unsure how to answer this question, answer N.
+config SECURITY_PERF_EVENTS_RESTRICT
+ bool "Restrict unprivileged use of performance events"
+ depends on PERF_EVENTS
+ help
+ If you say Y here, the kernel.perf_event_paranoid sysctl
+ will be set to 3 by default, and no unprivileged use of the
+ perf_event_open syscall will be permitted unless it is
+ changed.
+
config SECURITY
bool "Enable different security models"
depends on SYSFS
--
2.8.0.rc3.226.g39d4020
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