From 3d07cba37a6639f800a1ef49e115ccdba9a0f2ac Mon Sep 17 00:00:00 2001 From: Jeff Vander Stoep Date: Sun, 29 May 2016 14:22:32 -0700 Subject: [PATCH] ANDROID: 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. https://lkml.org/lkml/2016/1/11/587 Signed-off-by: Ben Hutchings Bug: 29054680 Change-Id: Iff5bff4fc1042e85866df9faa01bce8d04335ab8 --- Documentation/sysctl/kernel.txt | 4 +++- include/linux/perf_event.h | 5 +++++ kernel/events/core.c | 8 ++++++++ security/Kconfig | 9 +++++++++ 4 files changed, 25 insertions(+), 1 deletion(-) diff --git a/Documentation/sysctl/kernel.txt b/Documentation/sysctl/kernel.txt index 37a679501ddc..0e4a8129e86f 100644 --- a/Documentation/sysctl/kernel.txt +++ b/Documentation/sysctl/kernel.txt @@ -693,7 +693,8 @@ 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 @@ -701,6 +702,7 @@ 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 ============================================================== diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h index 53c500f0ca79..15c236b8aba3 100644 --- a/include/linux/perf_event.h +++ b/include/linux/perf_event.h @@ -1179,6 +1179,11 @@ 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 2a62b96600ad..67a4d5fd1b41 100644 --- 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 */ @@ -10408,6 +10413,9 @@ 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 27d8b2688f75..70af4cd55f03 100644 --- 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