From e88769f04a4f050e02980f776942c28431e56faf Mon Sep 17 00:00:00 2001 From: Ben Hutchings Date: Tue, 16 Aug 2016 10:27:00 -0600 Subject: [PATCH] UBUNTU: SAUCE: security,perf: Allow further restriction of perf_event_open https://lkml.org/lkml/2016/1/11/587 The GRKERNSEC_PERF_HARDEN feature extracted from grsecurity. Adds the option to disable perf_event_open() entirely for unprivileged users. This standalone version doesn't include making the variable read-only (or renaming it). 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 Signed-off-by: Tim Gardner [ saf: resolve conflicts with v5.8-rc1 ] Signed-off-by: Seth Forshee [ arighi: resolve conflicts with v6.2-rc2 ] Signed-off-by: Andrea Righi --- include/linux/perf_event.h | 6 ++++++ kernel/events/core.c | 8 ++++++++ security/Kconfig | 9 +++++++++ 3 files changed, 23 insertions(+) diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h index d2a15c0c6f8a..513fea882192 100644 --- a/include/linux/perf_event.h +++ b/include/linux/perf_event.h @@ -1612,6 +1612,12 @@ int perf_event_max_stack_handler(struct ctl_table *table, int write, #define PERF_SECURITY_CPU 1 #define PERF_SECURITY_KERNEL 2 #define PERF_SECURITY_TRACEPOINT 3 +#define PERF_SECURITY_MAX 4 + +static inline bool perf_paranoid_any(void) +{ + return sysctl_perf_event_paranoid >= PERF_SECURITY_MAX; +} static inline int perf_is_paranoid(void) { diff --git a/kernel/events/core.c b/kernel/events/core.c index f0f0f71213a1..81490911aeb1 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 + * 4 - disallow all unpriv perf event use */ +#ifdef CONFIG_SECURITY_PERF_EVENTS_RESTRICT +int sysctl_perf_event_paranoid __read_mostly = PERF_SECURITY_MAX; +#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 */ @@ -12440,6 +12445,9 @@ 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 52c9af08ad35..2a4686048fff 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