From f7271649bb1d0219a331cda6dfe6e2995b9144a9 Mon Sep 17 00:00:00 2001 From: Ben Hutchings Date: Mon, 11 Jan 2016 15:23:55 +0000 Subject: [PATCH] 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 Gbp-Pq: Topic features/all Gbp-Pq: Name security-perf-allow-further-restriction-of-perf_event_open.patch --- include/linux/perf_event.h | 5 +++++ kernel/events/core.c | 8 ++++++++ security/Kconfig | 9 +++++++++ 3 files changed, 22 insertions(+) diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h index 0031f7b4d9a..20220b3542e 100644 --- a/include/linux/perf_event.h +++ b/include/linux/perf_event.h @@ -1387,6 +1387,11 @@ 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 *buffer, size_t *lenp, loff_t *ppos); +static inline bool perf_paranoid_any(void) +{ + return sysctl_perf_event_paranoid > 2; +} + /* Access to perf_event_open(2) syscall. */ #define PERF_SECURITY_OPEN 0 diff --git a/kernel/events/core.c b/kernel/events/core.c index 7699b99706a..7e793bf5b7a 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -415,8 +415,13 @@ static struct kmem_cache *perf_event_cache; * 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 */ @@ -12235,6 +12240,9 @@ SYSCALL_DEFINE5(perf_event_open, if (err) return err; + 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) diff --git a/security/Kconfig b/security/Kconfig index e6db09a779b..037dc2baba2 100644 --- a/security/Kconfig +++ b/security/Kconfig @@ -19,6 +19,15 @@ 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 -- 2.30.2