From: David Howells Date: Wed, 24 May 2017 14:56:05 +0100 Subject: [27/29] bpf: Restrict kernel image access functions when the kernel is locked down Origin: https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git/commit?id=a13e9f58894129d9fd02fdb81b56ac7590704155 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 [bwh: Adjust context to apply after commit dcab51f19b29 "bpf: Expose check_uarg_tail_zero()"] --- kernel/bpf/syscall.c | 3 +++ 1 file changed, 3 insertions(+) Index: linux/kernel/bpf/syscall.c =================================================================== --- linux.orig/kernel/bpf/syscall.c +++ linux/kernel/bpf/syscall.c @@ -2378,6 +2378,9 @@ SYSCALL_DEFINE3(bpf, int, cmd, union bpf 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;