nr_args--;
}
- if ((prog->expected_attach_type == BPF_TRACE_FEXIT ||
- prog->expected_attach_type == BPF_MODIFY_RETURN) &&
- arg == nr_args) {
- if (!t)
- /* Default prog with 5 args. 6th arg is retval. */
- return true;
- /* function return type */
- t = btf_type_by_id(btf, t->type);
+ if (arg == nr_args) {
+ if (prog->expected_attach_type == BPF_TRACE_FEXIT) {
+ if (!t)
+ return true;
+ t = btf_type_by_id(btf, t->type);
+ } else if (prog->expected_attach_type == BPF_MODIFY_RETURN) {
+ /* For now the BPF_MODIFY_RETURN can only be attached to
+ * functions that return an int.
+ */
+ if (!t)
+ return false;
+
+ t = btf_type_skip_modifiers(btf, t->type, NULL);
+ if (!btf_type_is_int(t)) {
+ bpf_log(log,
+ "ret type %s not allowed for fmod_ret\n",
+ btf_kind_str[BTF_INFO_KIND(t->info)]);
+ return false;
+ }
+ }
} else if (arg >= nr_args) {
bpf_log(log, "func '%s' doesn't have %d-th argument\n",
tname, arg + 1);
#include <linux/sort.h>
#include <linux/perf_event.h>
#include <linux/ctype.h>
+#include <linux/error-injection.h>
#include "disasm.h"
return 0;
}
+#define SECURITY_PREFIX "security_"
+
+static int check_attach_modify_return(struct bpf_verifier_env *env)
+{
+ struct bpf_prog *prog = env->prog;
+ unsigned long addr = (unsigned long) prog->aux->trampoline->func.addr;
+
+ if (within_error_injection_list(addr))
+ return 0;
+
+ /* This is expected to be cleaned up in the future with the KRSI effort
+ * introducing the LSM_HOOK macro for cleaning up lsm_hooks.h.
+ */
+ if (!strncmp(SECURITY_PREFIX, prog->aux->attach_func_name,
+ sizeof(SECURITY_PREFIX) - 1)) {
+
+ if (!capable(CAP_MAC_ADMIN))
+ return -EPERM;
+
+ return 0;
+ }
+
+ verbose(env, "fmod_ret attach_btf_id %u (%s) is not modifiable\n",
+ prog->aux->attach_btf_id, prog->aux->attach_func_name);
+
+ return -EINVAL;
+}
static int check_attach_btf_id(struct bpf_verifier_env *env)
{
}
tr->func.addr = (void *)addr;
prog->aux->trampoline = tr;
+
+ if (prog->expected_attach_type == BPF_MODIFY_RETURN)
+ ret = check_attach_modify_return(env);
out:
mutex_unlock(&tr->mutex);
if (ret)