From: KP Singh <kpsingh@xxxxxxxxxx>
The helper allows modification of certain bits on the linux_binprm
struct starting with the secureexec bit which can be updated using the
BPF_LSM_F_BPRM_SECUREEXEC flag.
secureexec can be set by the LSM for privilege gaining executions to set
the AT_SECURE auxv for glibc. When set, the dynamic linker disables the
use of certain environment variables (like LD_PRELOAD).
Signed-off-by: KP Singh <kpsingh@xxxxxxxxxx>
---
include/uapi/linux/bpf.h | 14 ++++++++++++++
kernel/bpf/bpf_lsm.c | 20 ++++++++++++++++++++
scripts/bpf_helpers_doc.py | 2 ++
tools/include/uapi/linux/bpf.h | 14 ++++++++++++++
4 files changed, 50 insertions(+)
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 162999b12790..ed4f575be3d3 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -3787,6 +3787,14 @@ union bpf_attr {
* *ARG_PTR_TO_BTF_ID* of type *task_struct*.
* Return
* Pointer to the current task.
+ *
+ * void bpf_lsm_set_bprm_opts(struct linux_binprm *bprm, u64 flags)
+ *
+ * Description
+ * Sets certain options on the *bprm*:
+ *
+ * **BPF_LSM_F_BPRM_SECUREEXEC** Set the secureexec bit
+ * which sets the **AT_SECURE** auxv for glibc.
*/
#define __BPF_FUNC_MAPPER(FN) \
FN(unspec), \
@@ -3948,6 +3956,7 @@ union bpf_attr {
FN(task_storage_get), \
FN(task_storage_delete), \
FN(get_current_task_btf), \
+ FN(lsm_set_bprm_opts), \
/* */
/* integer value in 'imm' field of BPF_CALL instruction selects which helper
@@ -4119,6 +4128,11 @@ enum bpf_lwt_encap_mode {
BPF_LWT_ENCAP_IP,
};
+/* Flags for LSM helpers */
+enum {
+ BPF_LSM_F_BPRM_SECUREEXEC = (1ULL << 0),
+};
+
#define __bpf_md_ptr(type, name) \
union { \
type name; \
diff --git a/kernel/bpf/bpf_lsm.c b/kernel/bpf/bpf_lsm.c
index 553107f4706a..4d04fc490a14 100644
--- a/kernel/bpf/bpf_lsm.c
+++ b/kernel/bpf/bpf_lsm.c
@@ -7,6 +7,7 @@
#include <linux/filter.h>
#include <linux/bpf.h>
#include <linux/btf.h>
+#include <linux/binfmts.h>
#include <linux/lsm_hooks.h>
#include <linux/bpf_lsm.h>
#include <linux/kallsyms.h>
@@ -51,6 +52,23 @@ int bpf_lsm_verify_prog(struct bpf_verifier_log *vlog,
return 0;
}
+BPF_CALL_2(bpf_lsm_set_bprm_opts, struct linux_binprm *, bprm, u64, flags)
+{
+ bprm->secureexec = (flags & BPF_LSM_F_BPRM_SECUREEXEC);
+ return 0;
+}
+
+BTF_ID_LIST_SINGLE(bpf_lsm_set_bprm_opts_btf_ids, struct, linux_binprm)
+
+const static struct bpf_func_proto bpf_lsm_set_bprm_opts_proto = {
+ .func = bpf_lsm_set_bprm_opts,
+ .gpl_only = false,
+ .ret_type = RET_VOID,
+ .arg1_type = ARG_PTR_TO_BTF_ID,
+ .arg1_btf_id = &bpf_lsm_set_bprm_opts_btf_ids[0],
+ .arg2_type = ARG_ANYTHING,
+};
+
static const struct bpf_func_proto *
bpf_lsm_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
{
@@ -71,6 +89,8 @@ bpf_lsm_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
return &bpf_task_storage_get_proto;
case BPF_FUNC_task_storage_delete:
return &bpf_task_storage_delete_proto;
+ case BPF_FUNC_lsm_set_bprm_opts:
+ return &bpf_lsm_set_bprm_opts_proto;
default:
return tracing_prog_func_proto(func_id, prog);
}
diff --git a/scripts/bpf_helpers_doc.py b/scripts/bpf_helpers_doc.py
index 31484377b8b1..c5bc947a70ad 100755
--- a/scripts/bpf_helpers_doc.py
+++ b/scripts/bpf_helpers_doc.py
@@ -418,6 +418,7 @@ class PrinterHelpers(Printer):
'struct bpf_tcp_sock',
'struct bpf_tunnel_key',
'struct bpf_xfrm_state',
+ 'struct linux_binprm',
'struct pt_regs',
'struct sk_reuseport_md',
'struct sockaddr',
@@ -465,6 +466,7 @@ class PrinterHelpers(Printer):
'struct bpf_tcp_sock',
'struct bpf_tunnel_key',
'struct bpf_xfrm_state',
+ 'struct linux_binprm',
'struct pt_regs',
'struct sk_reuseport_md',
'struct sockaddr',
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 162999b12790..ed4f575be3d3 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -3787,6 +3787,14 @@ union bpf_attr {
* *ARG_PTR_TO_BTF_ID* of type *task_struct*.
* Return
* Pointer to the current task.
+ *
+ * void bpf_lsm_set_bprm_opts(struct linux_binprm *bprm, u64 flags)
+ *
+ * Description
+ * Sets certain options on the *bprm*:
+ *
+ * **BPF_LSM_F_BPRM_SECUREEXEC** Set the secureexec bit
+ * which sets the **AT_SECURE** auxv for glibc.
*/
#define __BPF_FUNC_MAPPER(FN) \
FN(unspec), \
@@ -3948,6 +3956,7 @@ union bpf_attr {
FN(task_storage_get), \
FN(task_storage_delete), \
FN(get_current_task_btf), \
+ FN(lsm_set_bprm_opts), \
/* */
/* integer value in 'imm' field of BPF_CALL instruction selects which helper
@@ -4119,6 +4128,11 @@ enum bpf_lwt_encap_mode {
BPF_LWT_ENCAP_IP,
};
+/* Flags for LSM helpers */
+enum {
+ BPF_LSM_F_BPRM_SECUREEXEC = (1ULL << 0),
+};
+
#define __bpf_md_ptr(type, name) \
union { \
type name; \
--
2.29.2.299.gdc1121823c-goog
