[PATCH V31 21/25] Lock down kprobes when in confidentiality mode

[Matthew Garrett]

From: David Howells <dhowells at redhat.com>

Disallow the creation of 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.

Reported-by: Alexei Starovoitov <alexei.starovoitov at gmail.com>
Signed-off-by: David Howells <dhowells at redhat.com>
Signed-off-by: Matthew Garrett <mjg59 at google.com>
Cc: Naveen N. Rao <naveen.n.rao at linux.ibm.com>
Cc: Anil S Keshavamurthy <anil.s.keshavamurthy at intel.com>
Cc: davem at davemloft.net
Cc: Masami Hiramatsu <mhiramat at kernel.org>
---
 kernel/kprobes.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index f4ddfdd2d07e..b9781bd2db8c 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -1552,6 +1552,9 @@ int register_kprobe(struct kprobe *p)
 	struct module *probed_mod;
 	kprobe_opcode_t *addr;
 
+	if (kernel_is_locked_down("Use of kprobes", LOCKDOWN_CONFIDENTIALITY))
+		return -EPERM;
+
 	/* Adjust probe address from symbol */
 	addr = kprobe_addr(p);
 	if (IS_ERR(addr))
-- 
2.21.0.392.gf8f6787159e-goog