From: Ben Hutchings Date: Mon, 11 Jan 2016 15:23:55 +0000 Subject: security,perf: Allow further restriction of perf_event_open Forwarded: https://lore.kernel.org/all/20160111152355.GS28542@decadent.org.uk/ 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 --- include/linux/perf_event.h | 5 +++++ kernel/events/core.c | 8 ++++++++ security/Kconfig | 9 +++++++++ 3 files changed, 22 insertions(+) --- a/include/linux/perf_event.h +++ b/include/linux/perf_event.h @@ -1617,6 +1617,11 @@ int perf_cpu_time_max_percent_handler(co int perf_event_max_stack_handler(const 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 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -449,8 +449,13 @@ static struct kmem_cache *perf_event_cac * 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 */ @@ -12681,6 +12686,9 @@ 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) --- a/security/Kconfig +++ b/security/Kconfig @@ -51,6 +51,15 @@ config PROC_MEM_NO_FORCE endchoice +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