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Commit 9d1f8be5 authored by David Howells's avatar David Howells Committed by James Morris
Browse files

bpf: Restrict bpf when kernel lockdown is in confidentiality mode 



bpf_read() and bpf_read_str() could potentially be abused to (eg) allow
private keys in kernel memory to be leaked. Disable them if the kernel
has been locked down in confidentiality mode.

Suggested-by: default avatarAlexei Starovoitov <alexei.starovoitov@gmail.com>
Signed-off-by: default avatarMatthew Garrett <mjg59@google.com>
Reviewed-by: default avatarKees Cook <keescook@chromium.org>
cc: netdev@vger.kernel.org
cc: Chun-Yi Lee <jlee@suse.com>
cc: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: default avatarJames Morris <jmorris@namei.org>
parent a94549dd

include/linux/security.h

+1 −0
Original line number Diff line number Diff line
@@ -118,6 +118,7 @@ enum lockdown_reason { 
	LOCKDOWN_INTEGRITY_MAX,

	LOCKDOWN_KCORE,

	LOCKDOWN_KPROBES,

	LOCKDOWN_BPF_READ,

	LOCKDOWN_CONFIDENTIALITY_MAX,

};

kernel/trace/bpf_trace.c

+10 −0
Original line number Diff line number Diff line
@@ -139,8 +139,13 @@ BPF_CALL_3(bpf_probe_read, void *, dst, u32, size, const void *, unsafe_ptr) 
{

	int ret;



	ret = security_locked_down(LOCKDOWN_BPF_READ);

	if (ret < 0)

		goto out;



	ret = probe_kernel_read(dst, unsafe_ptr, size);

	if (unlikely(ret < 0))

out:

		memset(dst, 0, size);



	return ret;
@@ -566,6 +571,10 @@ BPF_CALL_3(bpf_probe_read_str, void *, dst, u32, size, 
{

	int ret;



	ret = security_locked_down(LOCKDOWN_BPF_READ);

	if (ret < 0)

		goto out;



	/*

	 * The strncpy_from_unsafe() call will likely not fill the entire

	 * buffer, but that's okay in this circumstance as we're probing
@@ -577,6 +586,7 @@ BPF_CALL_3(bpf_probe_read_str, void *, dst, u32, size, 
	 */

	ret = strncpy_from_unsafe(dst, unsafe_ptr, size);

	if (unlikely(ret < 0))

out:

		memset(dst, 0, size);



	return ret;

security/lockdown/lockdown.c

+1 −0
Original line number Diff line number Diff line
@@ -33,6 +33,7 @@ static char *lockdown_reasons[LOCKDOWN_CONFIDENTIALITY_MAX+1] = { 
	[LOCKDOWN_INTEGRITY_MAX] = "integrity",

	[LOCKDOWN_KCORE] = "/proc/kcore access",

	[LOCKDOWN_KPROBES] = "use of kprobes",

	[LOCKDOWN_BPF_READ] = "use of bpf to read kernel RAM",

	[LOCKDOWN_CONFIDENTIALITY_MAX] = "confidentiality",

};