diff mbox series

[24/27] bpf: Restrict kernel image access functions when the kernel is locked down

Message ID 20190228231203.212359-24-matthewgarrett@google.com (mailing list archive)
State New, archived
Headers show
Series [PULL,REQUEST] Lock down patches | expand

Commit Message

Matthew Garrett Feb. 28, 2019, 11:12 p.m. UTC 
From: David Howells <dhowells@redhat.com>

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 <alexei.starovoitov@gmail.com>
Signed-off-by: David Howells <dhowells@redhat.com>
cc: netdev@vger.kernel.org
cc: Chun-Yi Lee <jlee@suse.com>
cc: Alexei Starovoitov <alexei.starovoitov@gmail.com>
---
 kernel/bpf/syscall.c | 3 +++
 1 file changed, 3 insertions(+)
diff mbox series

Patch

diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 8577bb7f8be6..e78dbe5473c9 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -2593,6 +2593,9 @@  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;