From 75d8d17e3575830e95225de69c3ee0cf66a85447 Mon Sep 17 00:00:00 2001 From: "Lee, Chun-Yi" Date: Wed, 23 Nov 2016 13:52:16 +0000 Subject: [PATCH] UBUNTU: SAUCE: (efi-lockdown) bpf: Restrict kernel image access functions when the kernel is locked down There are some bpf functions can be used to read kernel memory: bpf_probe_read, bpf_probe_write_user and bpf_trace_printk. These allow private keys in kernel memory (e.g. the hibernation image signing key) to be read by an eBPF program. Prohibit those functions when the kernel is locked down. Signed-off-by: Lee, Chun-Yi Signed-off-by: David Howells (cherry picked from commit 59e44bdc67df6cdcd4627f2b5b0b4d7e735c23fc git://git.kernel.org/pub/scm/linux/kernel/git/jwboyer/fedora.git) Signed-off-by: Seth Forshee --- kernel/trace/bpf_trace.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c index dc498b605d5d..fb240222b89b 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -65,6 +65,11 @@ BPF_CALL_3(bpf_probe_read, void *, dst, u32, size, const void *, unsafe_ptr) { int ret; + if (kernel_is_locked_down()) { + memset(dst, 0, size); + return -EPERM; + } + ret = probe_kernel_read(dst, unsafe_ptr, size); if (unlikely(ret < 0)) memset(dst, 0, size); @@ -84,6 +89,9 @@ static const struct bpf_func_proto bpf_probe_read_proto = { BPF_CALL_3(bpf_probe_write_user, void *, unsafe_ptr, const void *, src, u32, size) { + if (kernel_is_locked_down()) + return -EPERM; + /* * Ensure we're in user context which is safe for the helper to * run. This helper has no business in a kthread. @@ -143,6 +151,9 @@ BPF_CALL_5(bpf_trace_printk, char *, fmt, u32, fmt_size, u64, arg1, if (fmt[--fmt_size] != 0) return -EINVAL; + if (kernel_is_locked_down()) + return __trace_printk(1, fmt, 0, 0, 0); + /* check format string for allowed specifiers */ for (i = 0; i < fmt_size; i++) { if ((!isprint(fmt[i]) && !isspace(fmt[i])) || !isascii(fmt[i])) -- 2.39.5