Lock down kprobes

Disallow the creation of kprobes when the kernel is locked down by
preventing their registration.  This prevents kprobes from being used to
access kernel memory, either to make modifications or to steal crypto data.

Reported-by: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Gbp-Pq: Topic features/all/lockdown
Gbp-Pq: Name 0026-Lock-down-kprobes.patch

diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index f3183ad10d9617c3be730cecbf89fbc7d136734b..cf66b836681ca536611f4b21739f4fcf8b4b4081 100644 (file)
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -1561,6 +1561,9 @@ int register_kprobe(struct kprobe *p)
        struct module *probed_mod;
        kprobe_opcode_t *addr;
 
+       if (kernel_is_locked_down("Use of kprobes"))
+               return -EPERM;
+
        /* Adjust probe address from symbol */
        addr = kprobe_addr(p);
        if (IS_ERR(addr))