[RFC,bpf-next,seccomp,08/12] seccomp-ebpf: restrict filter to almost cBPF if LSM request such

Commit Message

YiFei Zhu May 10, 2021, 5:22 p.m. UTC

From: YiFei Zhu <[e-mail]>

If LSM hook security_seccomp_extended returns non-zero, seccomp-eBPF
filters are not permitted to use eBPF maps or helpers.

Signed-off-by: YiFei Zhu <[e-mail]>
---
 kernel/seccomp.c | 9 +++++++++
 1 file changed, 9 insertions(+)

Patch

diff --git a/kernel/seccomp.c b/kernel/seccomp.c
index 8550ae885245..b9ed9951a05b 100644
--- a/kernel/seccomp.c
+++ b/kernel/seccomp.c
@@ -2441,6 +2441,9 @@  static bool seccomp_is_valid_access(int off, int size,
 static const struct bpf_func_proto *
 seccomp_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 {
+	if (security_seccomp_extended())
+		return NULL;
+
 	switch (func_id) {
 	case BPF_FUNC_get_current_uid_gid:
 		return &bpf_get_current_uid_gid_proto;
@@ -2459,9 +2462,15 @@  seccomp_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 const struct bpf_prog_ops seccomp_prog_ops = {
 };
 
+static bool seccomp_map_access(enum bpf_access_type type)
+{
+	return !security_seccomp_extended();
+}
+
 const struct bpf_verifier_ops seccomp_verifier_ops = {
 	.get_func_proto		= seccomp_func_proto,
 	.is_valid_access	= seccomp_is_valid_access,
+	.map_access		= seccomp_map_access,
 };
 #endif /* CONFIG_SECCOMP_FILTER_EXTENDED */