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Subject[PATCH 1/4] perf_counter: Default to higher paranoia level
Change the default permissions on perf counters.

The new default will disallow regular users to create cpu-wide
counters, and will anonymize kernel IPs for task samples.

This will allow a user to profile his own applications and still know
the proportion of the kernel events, but does not expose kernel IPs.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Jens Axboe <jens.axboe@oracle.com>
---
arch/x86/kernel/cpu/perf_counter.c | 6 ++++++
include/linux/perf_counter.h | 1 +
kernel/perf_counter.c | 27 ++++++++++++++++++++-------
3 files changed, 27 insertions(+), 7 deletions(-)

Index: linux-2.6/arch/x86/kernel/cpu/perf_counter.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/cpu/perf_counter.c
+++ linux-2.6/arch/x86/kernel/cpu/perf_counter.c
@@ -2153,7 +2153,13 @@ static const struct stacktrace_ops backt
static void
perf_callchain_kernel(struct pt_regs *regs, struct perf_callchain_entry *entry)
{
+ u64 anon_ip = perf_paranoid_anon_ip();
+
callchain_store(entry, PERF_CONTEXT_KERNEL);
+ if (anon_ip) {
+ callchain_store(entry, anon_ip);
+ return;
+ }
callchain_store(entry, regs->ip);

dump_trace(NULL, regs, NULL, 0, &backtrace_ops, entry);
Index: linux-2.6/include/linux/perf_counter.h
===================================================================
--- linux-2.6.orig/include/linux/perf_counter.h
+++ linux-2.6/include/linux/perf_counter.h
@@ -754,6 +754,7 @@ static inline void perf_counter_mmap(str
extern void perf_counter_comm(struct task_struct *tsk);
extern void perf_counter_fork(struct task_struct *tsk);

+extern unsigned long perf_paranoid_anon_ip(void);
extern struct perf_callchain_entry *perf_callchain(struct pt_regs *regs);

extern int sysctl_perf_counter_paranoid;
Index: linux-2.6/kernel/perf_counter.c
===================================================================
--- linux-2.6.orig/kernel/perf_counter.c
+++ linux-2.6/kernel/perf_counter.c
@@ -48,18 +48,29 @@ static atomic_t nr_task_counters __read_
* perf counter paranoia level:
* 0 - not paranoid
* 1 - disallow cpu counters to unpriv
- * 2 - disallow kernel profiling to unpriv
+ * 2 - anonymize kernel RIPs to unpriv
+ * 3 - disallow kernel profiling to unpriv
*/
-int sysctl_perf_counter_paranoid __read_mostly;
+int sysctl_perf_counter_paranoid __read_mostly = 2;

static inline bool perf_paranoid_cpu(void)
{
- return sysctl_perf_counter_paranoid > 0;
+ return !capable(CAP_SYS_ADMIN) && sysctl_perf_counter_paranoid > 0;
+}
+
+static inline bool perf_paranoid_anon(void)
+{
+ return !capable(CAP_SYS_ADMIN) && sysctl_perf_counter_paranoid > 1;
}

static inline bool perf_paranoid_kernel(void)
{
- return sysctl_perf_counter_paranoid > 1;
+ return !capable(CAP_SYS_ADMIN) && sysctl_perf_counter_paranoid > 2;
+}
+
+unsigned long perf_paranoid_anon_ip(void)
+{
+ return perf_paranoid_anon() ? _THIS_IP_ : 0;
}

int sysctl_perf_counter_mlock __read_mostly = 512; /* 'free' kb per user */
@@ -1571,7 +1582,7 @@ static struct perf_counter_context *find
*/
if (cpu != -1) {
/* Must be root to operate on a CPU counter: */
- if (perf_paranoid_cpu() && !capable(CAP_SYS_ADMIN))
+ if (perf_paranoid_cpu())
return ERR_PTR(-EACCES);

if (cpu < 0 || cpu > num_possible_cpus())
@@ -2841,7 +2852,9 @@ void perf_counter_output(struct perf_cou
header.misc |= perf_misc_flags(data->regs);

if (sample_type & PERF_SAMPLE_IP) {
- ip = perf_instruction_pointer(data->regs);
+ ip = perf_paranoid_anon_ip();
+ if (!ip || user_mode(data->regs))
+ ip = perf_instruction_pointer(data->regs);
header.size += sizeof(ip);
}

@@ -4227,7 +4240,7 @@ SYSCALL_DEFINE5(perf_counter_open,
return ret;

if (!attr.exclude_kernel) {
- if (perf_paranoid_kernel() && !capable(CAP_SYS_ADMIN))
+ if (perf_paranoid_kernel())
return -EACCES;
}

--



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