lockdown: Lock down tracing and perf kprobes when in confidentiality …

…mode Disallow the creation of perf and ftrace kprobes when the kernel is locked down in confidentiality mode by preventing their registration. This prevents kprobes from being used to access kernel memory to steal crypto data, but continues to allow the use of kprobes from signed modules. Reported-by: Alexei Starovoitov <[email protected]> Signed-off-by: David Howells <[email protected]> Signed-off-by: Matthew Garrett <[email protected]> Acked-by: Masami Hiramatsu <[email protected]> Reviewed-by: Kees Cook <[email protected]> Cc: Naveen N. Rao <[email protected]> Cc: Anil S Keshavamurthy <[email protected]> Cc: [email protected] Cc: Masami Hiramatsu <[email protected]> Signed-off-by: James Morris <[email protected]>
josf · Aug 20, 2019 · a94549d · a94549d
1 parent 02e935b
commit a94549d
Show file tree

Hide file tree

Showing 3 changed files with 7 additions and 0 deletions.
diff --git a/include/linux/security.h b/include/linux/security.h
@@ -117,6 +117,7 @@ enum lockdown_reason {
 	LOCKDOWN_MMIOTRACE,
 	LOCKDOWN_INTEGRITY_MAX,
 	LOCKDOWN_KCORE,
+	LOCKDOWN_KPROBES,
 	LOCKDOWN_CONFIDENTIALITY_MAX,
 };
 

diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
@@ -11,6 +11,7 @@
 #include <linux/uaccess.h>
 #include <linux/rculist.h>
 #include <linux/error-injection.h>
+#include <linux/security.h>
 
 #include "trace_dynevent.h"
 #include "trace_kprobe_selftest.h"
@@ -415,6 +416,10 @@ static int __register_trace_kprobe(struct trace_kprobe *tk)
 {
 	int i, ret;
 
+	ret = security_locked_down(LOCKDOWN_KPROBES);
+	if (ret)
+		return ret;
+
 	if (trace_probe_is_registered(&tk->tp))
 		return -EINVAL;
 

diff --git a/security/lockdown/lockdown.c b/security/lockdown/lockdown.c
@@ -32,6 +32,7 @@ static char *lockdown_reasons[LOCKDOWN_CONFIDENTIALITY_MAX+1] = {
 	[LOCKDOWN_MMIOTRACE] = "unsafe mmio",
 	[LOCKDOWN_INTEGRITY_MAX] = "integrity",
 	[LOCKDOWN_KCORE] = "/proc/kcore access",
+	[LOCKDOWN_KPROBES] = "use of kprobes",
 	[LOCKDOWN_CONFIDENTIALITY_MAX] = "confidentiality",
 };