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Subject[PATCH] selinux: add tracepoint on denials
From
The audit data currently captures which process and which target
is responsible for a denial. There is no data on where exactly in the
process that call occurred. Debugging can be made easier by being able to
reconstruct the unified kernel and userland stack traces [1]. Add a
tracepoint on the SELinux denials which can then be used by userland
(i.e. perf).

Although this patch could manually be added by each OS developer to
trouble shoot a denial, adding it to the kernel streamlines the
developers workflow.

[1] https://source.android.com/devices/tech/debug/native_stack_dump

Signed-off-by: Thiébaud Weksteen <tweek@google.com>
Signed-off-by: Joel Fernandes <joelaf@google.com>
---
MAINTAINERS | 1 +
include/trace/events/selinux.h | 35 ++++++++++++++++++++++++++++++++++
security/selinux/avc.c | 6 ++++++
3 files changed, 42 insertions(+)
create mode 100644 include/trace/events/selinux.h

diff --git a/MAINTAINERS b/MAINTAINERS
index e64cdde81851..6b6cd5e13537 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -15358,6 +15358,7 @@ T: git git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/selinux.git
F: Documentation/ABI/obsolete/sysfs-selinux-checkreqprot
F: Documentation/ABI/obsolete/sysfs-selinux-disable
F: Documentation/admin-guide/LSM/SELinux.rst
+F: include/trace/events/selinux.h
F: include/uapi/linux/selinux_netlink.h
F: scripts/selinux/
F: security/selinux/
diff --git a/include/trace/events/selinux.h b/include/trace/events/selinux.h
new file mode 100644
index 000000000000..e247187a8135
--- /dev/null
+++ b/include/trace/events/selinux.h
@@ -0,0 +1,35 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM selinux
+
+#if !defined(_TRACE_SELINUX_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_SELINUX_H
+
+#include <linux/ktime.h>
+#include <linux/tracepoint.h>
+
+TRACE_EVENT(selinux_denied,
+
+ TP_PROTO(int cls, int av),
+
+ TP_ARGS(cls, av),
+
+ TP_STRUCT__entry(
+ __field(int, cls)
+ __field(int, av)
+ ),
+
+ TP_fast_assign(
+ __entry->cls = cls;
+ __entry->av = av;
+ ),
+
+ TP_printk("denied %d %d",
+ __entry->cls,
+ __entry->av)
+);
+
+#endif
+
+/* This part must be outside protection */
+#include <trace/define_trace.h>
diff --git a/security/selinux/avc.c b/security/selinux/avc.c
index d18cb32a242a..85d2e22ab656 100644
--- a/security/selinux/avc.c
+++ b/security/selinux/avc.c
@@ -31,6 +31,9 @@
#include "avc_ss.h"
#include "classmap.h"

+#define CREATE_TRACE_POINTS
+#include <trace/events/selinux.h>
+
#define AVC_CACHE_SLOTS 512
#define AVC_DEF_CACHE_THRESHOLD 512
#define AVC_CACHE_RECLAIM 16
@@ -672,6 +675,9 @@ static void avc_audit_pre_callback(struct audit_buffer *ab, void *a)
return;
}

+ if (sad->denied)
+ trace_selinux_denied(sad->tclass, av);
+
perms = secclass_map[sad->tclass-1].perms;

audit_log_format(ab, " {");
--
2.28.0.rc0.142.g3c755180ce-goog
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