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ANDROID: security,perf: Allow further restriction of perf_event_open

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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 <ben@decadent.org.uk>

Bug: 29054680
Change-Id: Iff5bff4fc1042e85866df9faa01bce8d04335ab8
This commit is contained in:
Jeff Vander Stoep 2016-05-29 14:22:32 -07:00 committed by Amit Pundir
parent 53dd96134b
commit 3d07cba37a
4 changed files with 25 additions and 1 deletions
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4
Documentation/sysctl/kernel.txt
View file

@ -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
==============================================================

5
include/linux/perf_event.h
View file

@ -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;

8
kernel/events/core.c
View file

@ -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;

9
security/Kconfig
View file

@ -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