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

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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 <alexei.starovoitov@gmail.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Matthew Garrett <mjg59@google.com>
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Cc: Naveen N. Rao <naveen.n.rao@linux.ibm.com>
Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Cc: davem@davemloft.net
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: James Morris <jmorris@namei.org>
This commit is contained in:
David Howells 2019-08-19 17:17:58 -07:00 committed by James Morris
parent 02e935bf5b
commit a94549dd87
3 changed files with 7 additions and 0 deletions
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1
include/linux/security.h
View File

@ -117,6 +117,7 @@ enum lockdown_reason {
LOCKDOWN_MMIOTRACE,
LOCKDOWN_INTEGRITY_MAX,
LOCKDOWN_KCORE,
LOCKDOWN_KPROBES,
LOCKDOWN_CONFIDENTIALITY_MAX,
};

5
kernel/trace/trace_kprobe.c
View File

@ -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;

1
security/lockdown/lockdown.c
View File

@ -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",
};