[linux] 01/01: security, perf: Allow unprivileged use of perf_event_open to be disabled

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benh pushed a commit to branch jessie
in repository linux.

commit 0523f19ca363a4c0013949323e6b87dfb4d87edb
Author: Ben Hutchings <ben at decadent.org.uk>
Date:   Sat Dec 10 04:45:32 2016 +0000

    security,perf: Allow unprivileged use of perf_event_open to be disabled
    
    ...but don't change the default here.
---
 debian/changelog                                   |  2 +
 ...ow-further-restriction-of-perf_event_open.patch | 75 ++++++++++++++++++++++
 debian/patches/series                              |  1 +
 3 files changed, 78 insertions(+)

diff --git a/debian/changelog b/debian/changelog
index 00c4da7..9f06e1f 100644
--- a/debian/changelog
+++ b/debian/changelog
@@ -509,6 +509,8 @@ linux (3.16.39-1) UNRELEASED; urgency=medium
   * [x86] KVM: drop error recovery in em_jmp_far and em_ret_far (CVE-2016-9756)
   * net: avoid signed overflows for SO_{SND|RCV}BUFFORCE (CVE-2016-9793)
   * ALSA: pcm : Call kill_fasync() in stream lock (CVE-2016-9794)
+  * security,perf: Allow unprivileged use of perf_event_open to be disabled
+    (sysctl: kernel.perf_event_paranoid=3)
 
   [ Julien Cristau ]
   * hwrng: Add chaoskey driver, backported from 4.8 (Closes: #839616)
diff --git a/debian/patches/features/all/security-perf-allow-further-restriction-of-perf_event_open.patch b/debian/patches/features/all/security-perf-allow-further-restriction-of-perf_event_open.patch
new file mode 100644
index 0000000..a0bb88c
--- /dev/null
+++ b/debian/patches/features/all/security-perf-allow-further-restriction-of-perf_event_open.patch
@@ -0,0 +1,75 @@
+From: Ben Hutchings <ben at decadent.org.uk>
+Date: Mon, 11 Jan 2016 15:23:55 +0000
+Subject: security,perf: Allow further restriction of perf_event_open
+Forwarded: https://lkml.org/lkml/2016/1/11/587
+
+When kernel.perf_event_open is set to 3 (or greater), disallow all
+access to performance events by users without CAP_SYS_ADMIN.
+Add a Kconfig symbol CONFIG_SECURITY_PERF_EVENTS_RESTRICT that
+makes this value the default.
+
+This is based on a similar feature in grsecurity
+(CONFIG_GRKERNSEC_PERF_HARDEN).  This version doesn't include making
+the variable read-only.  It also allows enabling further restriction
+at run-time regardless of whether the default is changed.
+
+Signed-off-by: Ben Hutchings <ben at decadent.org.uk>
+---
+--- a/include/linux/perf_event.h
++++ b/include/linux/perf_event.h
+@@ -731,6 +731,11 @@ extern int perf_cpu_time_max_percent_han
+ 		loff_t *ppos);
+ 
+ 
++static inline bool perf_paranoid_any(void)
++{
++	return sysctl_perf_event_paranoid > 2;
++}
++
+ static inline bool perf_paranoid_tracepoint_raw(void)
+ {
+ 	return sysctl_perf_event_paranoid > -1;
+--- a/kernel/events/core.c
++++ b/kernel/events/core.c
+@@ -161,8 +161,13 @@ static struct srcu_struct pmus_srcu;
+  *   0 - disallow raw tracepoint access for unpriv
+  *   1 - disallow cpu events for unpriv
+  *   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 = 1;
++#endif
+ 
+ /* Minimum for 512 kiB + 1 user control page */
+ int sysctl_perf_event_mlock __read_mostly = 512 + (PAGE_SIZE / 1024); /* 'free' kiB per user */
+@@ -7197,6 +7202,9 @@ SYSCALL_DEFINE5(perf_event_open,
+ 	if (flags & ~PERF_FLAG_ALL)
+ 		return -EINVAL;
+ 
++	if (perf_paranoid_any() && !capable(CAP_SYS_ADMIN))
++		return -EACCES;
++
+ 	err = perf_copy_attr(attr_uptr, &attr);
+ 	if (err)
+ 		return err;
+--- 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
diff --git a/debian/patches/series b/debian/patches/series
index 886d2d1..667a2ff 100644
--- a/debian/patches/series
+++ b/debian/patches/series
@@ -40,6 +40,7 @@ features/all/cgroups-Allow-memory-cgroup-support-to-be-included-b.patch
 debian/cgroups-Document-the-Debian-memory-resource-controll.patch
 debian/yama-disable-by-default.patch
 debian/add-sysctl-to-disallow-unprivileged-CLONE_NEWUSER-by-default.patch
+features/all/security-perf-allow-further-restriction-of-perf_event_open.patch
 
 # Disable autoloading/probing of various drivers by default
 debian/cirrus-disable-modeset-by-default.patch

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