[PATCH v4 bpf-next 3/4] perf: implement CAP_TRACING

From: Alexei Starovoitov <ast@kernel.org>
Date: 2019-09-06 23:11:05
Also in: bpf, linux-api
Subsystem: documentation, linux for powerpc (32-bit and 64-bit), performance events subsystem, the rest, tracing, x86 architecture (32-bit and 64-bit) · Maintainers: Jonathan Corbet, Madhavan Srinivasan, Michael Ellerman, Peter Zijlstra, Ingo Molnar, Arnaldo Carvalho de Melo, Namhyung Kim, Linus Torvalds, Steven Rostedt, Masami Hiramatsu, Thomas Gleixner, Borislav Petkov, Dave Hansen

Implement permissions as stated in uapi/linux/capability.h
and update Documentation.

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
---
 Documentation/admin-guide/perf-security.rst |  4 ++--
 Documentation/admin-guide/sysctl/kernel.rst | 10 ++++------
 arch/powerpc/perf/core-book3s.c             |  4 ++--
 arch/x86/events/intel/bts.c                 |  2 +-
 arch/x86/events/intel/core.c                |  2 +-
 arch/x86/events/intel/p4.c                  |  2 +-
 kernel/events/core.c                        | 14 +++++++-------
 kernel/events/hw_breakpoint.c               |  2 +-
 kernel/trace/trace_event_perf.c             |  4 ++--
 9 files changed, 21 insertions(+), 23 deletions(-)

diff --git a/Documentation/admin-guide/perf-security.rst b/Documentation/admin-guide/perf-security.rst
index 72effa7c23b9..c84152d1dfd4 100644
--- a/Documentation/admin-guide/perf-security.rst
+++ b/Documentation/admin-guide/perf-security.rst

@@ -66,8 +66,8 @@ into distinct units, known as capabilities [6]_ , which can be
 independently enabled and disabled on per-thread basis for processes and
 files of unprivileged users.
 
-Unprivileged processes with enabled CAP_SYS_ADMIN capability are treated
-as privileged processes with respect to perf_events performance
+Unprivileged processes with enabled CAP_SYS_ADMIN or CAP_TRACING capability
+are treated as privileged processes with respect to perf_events performance
 monitoring and bypass *scope* permissions checks in the kernel.
 
 Unprivileged processes using perf_events system call API is also subject

diff --git a/Documentation/admin-guide/sysctl/kernel.rst b/Documentation/admin-guide/sysctl/kernel.rst
index 032c7cd3cede..595bf2b1363f 100644
--- a/Documentation/admin-guide/sysctl/kernel.rst
+++ b/Documentation/admin-guide/sysctl/kernel.rst

@@ -720,20 +720,18 @@ allowed to execute.
 ====================
 
 Controls use of the performance events system by unprivileged
-users (without CAP_SYS_ADMIN).  The default value is 2.
+users (without CAP_SYS_ADMIN and without CAP_TRACING).  The default value is 2.
 
 ===  ==================================================================
  -1  Allow use of (almost) all events by all users
 
      Ignore mlock limit after perf_event_mlock_kb without CAP_IPC_LOCK
 
->=0  Disallow ftrace function tracepoint by users without CAP_SYS_ADMIN
+>=0  Disallow ftrace function tracepoint and raw tracepoint
 
-     Disallow raw tracepoint access by users without CAP_SYS_ADMIN
+>=1  Disallow CPU event access
 
->=1  Disallow CPU event access by users without CAP_SYS_ADMIN
-
->=2  Disallow kernel profiling by users without CAP_SYS_ADMIN
+>=2  Disallow kernel profiling
 ===  ==================================================================

diff --git a/arch/powerpc/perf/core-book3s.c b/arch/powerpc/perf/core-book3s.c
index ca92e01d0bd1..a204a3c6c68b 100644
--- a/arch/powerpc/perf/core-book3s.c
+++ b/arch/powerpc/perf/core-book3s.c

@@ -204,7 +204,7 @@ static inline void perf_get_data_addr(struct pt_regs *regs, u64 *addrp)
 	if (!(mmcra & MMCRA_SAMPLE_ENABLE) || sdar_valid)
 		*addrp = mfspr(SPRN_SDAR);
 
-	if (perf_paranoid_kernel() && !capable(CAP_SYS_ADMIN) &&
+	if (perf_paranoid_kernel() && !capable_tracing() &&
 		is_kernel_addr(mfspr(SPRN_SDAR)))
 		*addrp = 0;
 }

@@ -472,7 +472,7 @@ static void power_pmu_bhrb_read(struct cpu_hw_events *cpuhw)
 			 * exporting it to userspace (avoid exposure of regions
 			 * where we could have speculative execution)
 			 */
-			if (perf_paranoid_kernel() && !capable(CAP_SYS_ADMIN) &&
+			if (perf_paranoid_kernel() && !capable_tracing() &&
 				is_kernel_addr(addr))
 				continue;

diff --git a/arch/x86/events/intel/bts.c b/arch/x86/events/intel/bts.c
index 5ee3fed881d3..bd713b2dd7c2 100644
--- a/arch/x86/events/intel/bts.c
+++ b/arch/x86/events/intel/bts.c

@@ -550,7 +550,7 @@ static int bts_event_init(struct perf_event *event)
 	 * users to profile the kernel.
 	 */
 	if (event->attr.exclude_kernel && perf_paranoid_kernel() &&
-	    !capable(CAP_SYS_ADMIN))
+	    !capable_tracing())
 		return -EACCES;
 
 	if (x86_add_exclusive(x86_lbr_exclusive_bts))

diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c
index e4c2cb65ea50..a7f8c18bd82b 100644
--- a/arch/x86/events/intel/core.c
+++ b/arch/x86/events/intel/core.c

@@ -3307,7 +3307,7 @@ static int intel_pmu_hw_config(struct perf_event *event)
 	if (x86_pmu.version < 3)
 		return -EINVAL;
 
-	if (perf_paranoid_cpu() && !capable(CAP_SYS_ADMIN))
+	if (perf_paranoid_cpu() && !capable_tracing())
 		return -EACCES;
 
 	event->hw.config |= ARCH_PERFMON_EVENTSEL_ANY;

diff --git a/arch/x86/events/intel/p4.c b/arch/x86/events/intel/p4.c
index dee579efb2b2..f379a358c9cb 100644
--- a/arch/x86/events/intel/p4.c
+++ b/arch/x86/events/intel/p4.c

@@ -776,7 +776,7 @@ static int p4_validate_raw_event(struct perf_event *event)
 	 * the user needs special permissions to be able to use it
 	 */
 	if (p4_ht_active() && p4_event_bind_map[v].shared) {
-		if (perf_paranoid_cpu() && !capable(CAP_SYS_ADMIN))
+		if (perf_paranoid_cpu() && !capable_tracing())
 			return -EACCES;
 	}

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 0463c1151bae..eaba102e5d91 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c

@@ -4134,7 +4134,7 @@ find_get_context(struct pmu *pmu, struct task_struct *task,
 
 	if (!task) {
 		/* Must be root to operate on a CPU event: */
-		if (perf_paranoid_cpu() && !capable(CAP_SYS_ADMIN))
+		if (perf_paranoid_cpu() && !capable_tracing())
 			return ERR_PTR(-EACCES);
 
 		cpuctx = per_cpu_ptr(pmu->pmu_cpu_context, cpu);

@@ -8741,7 +8741,7 @@ static int perf_kprobe_event_init(struct perf_event *event)
 	if (event->attr.type != perf_kprobe.type)
 		return -ENOENT;
 
-	if (!capable(CAP_SYS_ADMIN))
+	if (!capable_tracing())
 		return -EACCES;
 
 	/*

@@ -8801,7 +8801,7 @@ static int perf_uprobe_event_init(struct perf_event *event)
 	if (event->attr.type != perf_uprobe.type)
 		return -ENOENT;
 
-	if (!capable(CAP_SYS_ADMIN))
+	if (!capable_tracing())
 		return -EACCES;
 
 	/*

@@ -10588,7 +10588,7 @@ static int perf_copy_attr(struct perf_event_attr __user *uattr,
 		}
 		/* privileged levels capture (kernel, hv): check permissions */
 		if ((mask & PERF_SAMPLE_BRANCH_PERM_PLM)
-		    && perf_paranoid_kernel() && !capable(CAP_SYS_ADMIN))
+		    && perf_paranoid_kernel() && !capable_tracing())
 			return -EACCES;
 	}

@@ -10807,12 +10807,12 @@ SYSCALL_DEFINE5(perf_event_open,
 		return err;
 
 	if (!attr.exclude_kernel) {
-		if (perf_paranoid_kernel() && !capable(CAP_SYS_ADMIN))
+		if (perf_paranoid_kernel() && !capable_tracing())
 			return -EACCES;
 	}
 
 	if (attr.namespaces) {
-		if (!capable(CAP_SYS_ADMIN))
+		if (!capable_tracing())
 			return -EACCES;
 	}

@@ -10826,7 +10826,7 @@ SYSCALL_DEFINE5(perf_event_open,
 
 	/* Only privileged users can get physical addresses */
 	if ((attr.sample_type & PERF_SAMPLE_PHYS_ADDR) &&
-	    perf_paranoid_kernel() && !capable(CAP_SYS_ADMIN))
+	    perf_paranoid_kernel() && !capable_tracing())
 		return -EACCES;
 
 	/*

diff --git a/kernel/events/hw_breakpoint.c b/kernel/events/hw_breakpoint.c
index c5cd852fe86b..8bc4d7d8c913 100644
--- a/kernel/events/hw_breakpoint.c
+++ b/kernel/events/hw_breakpoint.c

@@ -404,7 +404,7 @@ static int hw_breakpoint_parse(struct perf_event *bp,
 		 * Don't let unprivileged users set a breakpoint in the trap
 		 * path to avoid trap recursion attacks.
 		 */
-		if (!capable(CAP_SYS_ADMIN))
+		if (!capable_tracing())
 			return -EPERM;
 	}

diff --git a/kernel/trace/trace_event_perf.c b/kernel/trace/trace_event_perf.c
index 0892e38ed6fb..6861307f14d6 100644
--- a/kernel/trace/trace_event_perf.c
+++ b/kernel/trace/trace_event_perf.c

@@ -46,7 +46,7 @@ static int perf_trace_event_perm(struct trace_event_call *tp_event,
 
 	/* The ftrace function trace is allowed only for root. */
 	if (ftrace_event_is_function(tp_event)) {
-		if (perf_paranoid_tracepoint_raw() && !capable(CAP_SYS_ADMIN))
+		if (perf_paranoid_tracepoint_raw() && !capable_tracing())
 			return -EPERM;
 
 		if (!is_sampling_event(p_event))

@@ -82,7 +82,7 @@ static int perf_trace_event_perm(struct trace_event_call *tp_event,
 	 * ...otherwise raw tracepoint data can be a severe data leak,
 	 * only allow root to have these.
 	 */
-	if (perf_paranoid_tracepoint_raw() && !capable(CAP_SYS_ADMIN))
+	if (perf_paranoid_tracepoint_raw() && !capable_tracing())
 		return -EPERM;
 
 	return 0;

-- 
2.20.0

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