lockdown: Lock down perf when in confidentiality mode

Disallow the use of certain perf facilities that might allow userspace to
access kernel data.

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Matthew Garrett <mjg59@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Signed-off-by: James Morris <jmorris@namei.org>

diff --git a/include/linux/security.h b/include/linux/security.h
index e604f4c..b94f1e6 100644 (file)
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -119,6 +119,7 @@ enum lockdown_reason {
        LOCKDOWN_KCORE,
        LOCKDOWN_KPROBES,
        LOCKDOWN_BPF_READ,
+       LOCKDOWN_PERF,
        LOCKDOWN_CONFIDENTIALITY_MAX,
 };
 

diff --git a/kernel/events/core.c b/kernel/events/core.c
index f85929c..8732f98 100644 (file)
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -10798,6 +10798,13 @@ SYSCALL_DEFINE5(perf_event_open,
            perf_paranoid_kernel() && !capable(CAP_SYS_ADMIN))
                return -EACCES;
 
+       err = security_locked_down(LOCKDOWN_PERF);
+       if (err && (attr.sample_type & PERF_SAMPLE_REGS_INTR))
+               /* REGS_INTR can leak data, lockdown must prevent this */
+               return err;
+
+       err = 0;
+
        /*
         * In cgroup mode, the pid argument is used to pass the fd
         * opened to the cgroup directory in cgroupfs. The cpu argument

diff --git a/security/lockdown/lockdown.c b/security/lockdown/lockdown.c
index 2397772..3d7b103 100644 (file)
--- a/security/lockdown/lockdown.c
+++ b/security/lockdown/lockdown.c
@@ -34,6 +34,7 @@ static char *lockdown_reasons[LOCKDOWN_CONFIDENTIALITY_MAX+1] = {
        [LOCKDOWN_KCORE] = "/proc/kcore access",
        [LOCKDOWN_KPROBES] = "use of kprobes",
        [LOCKDOWN_BPF_READ] = "use of bpf to read kernel RAM",
+       [LOCKDOWN_PERF] = "unsafe use of perf",
        [LOCKDOWN_CONFIDENTIALITY_MAX] = "confidentiality",
 };