[PATCH V35 24/29] Lock down perf when in confidentiality mode
From: Matthew Garrett <hidden>
Date: 2019-07-15 20:01:04
Also in:
linux-security-module, lkml
Subsystem:
lockdown security module, performance events subsystem, security subsystem, the rest · Maintainers:
Nicolas Bouchinet, Xiu Jianfeng, Peter Zijlstra, Ingo Molnar, Arnaldo Carvalho de Melo, Namhyung Kim, Paul Moore, James Morris, "Serge E. Hallyn", Linus Torvalds
From: David Howells <dhowells@redhat.com> 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 <redacted> Reviewed-by: Kees Cook <redacted> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Ingo Molnar <mingo@redhat.com> Cc: Arnaldo Carvalho de Melo <acme@kernel.org> --- include/linux/security.h | 1 + kernel/events/core.c | 7 +++++++ security/lockdown/lockdown.c | 1 + 3 files changed, 9 insertions(+)
diff --git a/include/linux/security.h b/include/linux/security.h
index 8dd1741a52cd..8ef366de70b0 100644
--- 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 785d708f8553..738d6f1cf5ec 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c@@ -10806,6 +10806,13 @@ 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 d14b89784412..e43c9d001e49 100644
--- 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", };
--
2.22.0.510.g264f2c817a-goog