Revert "Revert "ANDROID: security,perf: Allow further restriction of perf_event_open""

This reverts commit 44a6aea9c2.

Change-Id: I6ee8a29e5e784c06c65b65302ad726651ded45b8
Signed-off-by: Srinivasarao P <spathi@codeaurora.org>
Signed-off-by: UtsavBalar1231 <utsavbalar1231@gmail.com>

Documentation/sysctl/kernel.txt

@@ -678,7 +678,8 @@ 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
      Ignore mlock limit after perf_event_mlock_kb without CAP_IPC_LOCK
@@ -686,6 +687,7 @@ users (without CAP_SYS_ADMIN).  The default value is 2.
      Disallow raw tracepoint access by users without CAP_SYS_ADMIN
 >=1: Disallow CPU event access by users without CAP_SYS_ADMIN
 >=2: Disallow kernel profiling by users without CAP_SYS_ADMIN
+>=3: Disallow all event access by users without CAP_SYS_ADMIN
 
 ==============================================================
 

arch/arm64/configs/cuttlefish_defconfig

@@ -466,6 +466,7 @@ CONFIG_RCU_CPU_STALL_TIMEOUT=60
 CONFIG_ENABLE_DEFAULT_TRACERS=y
 CONFIG_TEST_MEMINIT=y
 CONFIG_TEST_STACKINIT=y
+CONFIG_SECURITY_PERF_EVENTS_RESTRICT=y
 CONFIG_SECURITY=y
 CONFIG_SECURITY_NETWORK=y
 CONFIG_LSM_MMAP_MIN_ADDR=65536

arch/x86/configs/x86_64_cuttlefish_defconfig

@@ -499,6 +499,7 @@ CONFIG_TEST_STACKINIT=y
 CONFIG_IO_DELAY_NONE=y
 CONFIG_OPTIMIZE_INLINING=y
 CONFIG_UNWINDER_FRAME_POINTER=y
+CONFIG_SECURITY_PERF_EVENTS_RESTRICT=y
 CONFIG_SECURITY=y
 CONFIG_SECURITY_NETWORK=y
 CONFIG_SECURITY_PATH=y

include/linux/perf_event.h

@@ -1207,6 +1207,11 @@ int perf_event_max_stack_handler(struct ctl_table *table, int write,
 #define PERF_SECURITY_KERNEL		2
 #define PERF_SECURITY_TRACEPOINT	3
 
+static inline bool perf_paranoid_any(void)
+{
+	return sysctl_perf_event_paranoid > 2;
+}
+
 static inline int perf_is_paranoid(void)
 {
 	return sysctl_perf_event_paranoid > -1;

kernel/events/core.c

@@ -430,8 +430,13 @@ static cpumask_var_t perf_online_mask;
  *   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 = 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 */
@@ -10412,6 +10417,9 @@ SYSCALL_DEFINE5(perf_event_open,
 	if (flags & ~PERF_FLAG_ALL)
 		return -EINVAL;
 
+	if (perf_paranoid_any() && !capable(CAP_SYS_ADMIN))
+		return -EACCES;
+
 	/* Do we allow access to perf_event_open(2) ? */
 	err = security_perf_event_open(&attr, PERF_SECURITY_OPEN);
 	if (err)

security/Kconfig

@@ -22,6 +22,15 @@ 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