security,perf: Allow further restriction of perf_event_open

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@decadent.org.uk>
Gbp-Pq: Topic features/all
Gbp-Pq: Name security-perf-allow-further-restriction-of-perf_event_open.patch

diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 7546822a1d74f198d5c521bc2864c369e38d70e4..320033b310d2eaa0e17c9e69bea7b8858f55ba5d 100644 (file)
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -1151,6 +1151,11 @@ extern int perf_cpu_time_max_percent_handler(struct ctl_table *table, int write,
 int perf_event_max_stack_handler(struct ctl_table *table, int write,
                                 void __user *buffer, size_t *lenp, 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;

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 385480a5aa45d26f6bae0d677ba98ffa5fd225a8..fe31cfb2acb71119a5f0dcfc55429fb9a013d2a1 100644 (file)
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -397,8 +397,13 @@ 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 */
@@ -9883,6 +9888,9 @@ 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;

diff --git a/security/Kconfig b/security/Kconfig
index 3709db95027fecef40d872d4d142cdb9a9aac3cf..eceb91243b6e5a232299db034b65d98d331298a9 100644 (file)
--- 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