From 9333ebfaeb6ccc57a9f2dec371e8cd7a201b6476 Mon Sep 17 00:00:00 2001 From: David Howells Date: Mon, 18 Feb 2019 12:45:02 +0000 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 0025-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 42d17f73078..19633a810f5 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -2777,6 +2777,9 @@ 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 = bpf_check_uarg_tail_zero(uattr, sizeof(attr), size); if (err) return err; -- 2.30.2