From 34aa7ba32d5a5330927b575bf1c28d9e82ced709 Mon Sep 17 00:00:00 2001 From: David Howells Date: Wed, 24 May 2017 14:56:05 +0100 Subject: [PATCH] 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 and kernel memory to be altered without restriction. Completely prohibit the use of BPF when the kernel is locked down. Suggested-by: Alexei Starovoitov Signed-off-by: David Howells cc: netdev@vger.kernel.org cc: Chun-Yi Lee cc: Alexei Starovoitov Gbp-Pq: Topic features/all/lockdown Gbp-Pq: Name 0027-bpf-Restrict-kernel-image-access-functions-when-the-.patch --- kernel/bpf/syscall.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index 43f95d190ee..0295c95eb2f 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -1848,6 +1848,9 @@ SYSCALL_DEFINE3(bpf, int, cmd, union bpf_attr __user *, uattr, unsigned int, siz if (sysctl_unprivileged_bpf_disabled && !capable(CAP_SYS_ADMIN)) return -EPERM; + if (kernel_is_locked_down("BPF")) + return -EPERM; + err = check_uarg_tail_zero(uattr, sizeof(attr), size); if (err) return err; -- 2.30.2