On 2/21/23 16:17, Jiri Olsa wrote:
On Mon, Feb 20, 2023 at 11:42:52AM +0100, Viktor Malik wrote:
SNIP
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 388245e8826e..6da830df3ea5 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -24,6 +24,7 @@
#include <linux/bpf_lsm.h>
#include <linux/btf_ids.h>
#include <linux/poison.h>
+#include "../module/internal.h"
#include "disasm.h"
@@ -16868,6 +16869,7 @@ int bpf_check_attach_target(struct bpf_verifier_log *log,
const char *tname;
struct btf *btf;
long addr = 0;
+ struct module *mod = NULL;
if (!btf_id) {
bpf_log(log, "Tracing programs must provide btf_id\n");
@@ -17041,7 +17043,15 @@ int bpf_check_attach_target(struct bpf_verifier_log *log,
else
addr = (long) tgt_prog->aux->func[subprog]->bpf_func;
} else {
- addr = kallsyms_lookup_name(tname);
+ if (btf_is_module(btf)) {
+ mod = btf_try_get_module(btf);
+ if (mod)
+ addr = find_kallsyms_symbol_value(mod, tname);
+ else
+ addr = 0;
+ } else {
+ addr = kallsyms_lookup_name(tname);
+ }
there are some error paths below this point which I think we could
hit also for module id/address, so we need to put the mod ref
Right, I didn't notice those, thanks. I'll fix that.
also there's bpf_trampoline_link_cgroup_shim caller of
bpf_check_attach_target, but I'm not sure that could endup with
id/address in module code
I did check this and IIUC, this is for BPF_LSM_CGROUP programs and
bpf_lsm_* hooks are always placed in vmlinux, so this shouldn't occur.
Viktor
jirka
if (!addr) {
bpf_log(log,
"The address of function %s cannot be found\n",
@@ -17105,6 +17115,7 @@ int bpf_check_attach_target(struct bpf_verifier_log *log,
tgt_info->tgt_addr = addr;
tgt_info->tgt_name = tname;
tgt_info->tgt_type = t;
+ tgt_info->tgt_mod = mod;
return 0;
}
@@ -17184,6 +17195,7 @@ static int check_attach_btf_id(struct bpf_verifier_env *env)
/* store info about the attachment target that will be used later */
prog->aux->attach_func_proto = tgt_info.tgt_type;
prog->aux->attach_func_name = tgt_info.tgt_name;
+ prog->aux->mod = tgt_info.tgt_mod;
if (tgt_prog) {
prog->aux->saved_dst_prog_type = tgt_prog->type;
diff --git a/kernel/module/internal.h b/kernel/module/internal.h
index 2e2bf236f558..5cb103a46018 100644
--- a/kernel/module/internal.h
+++ b/kernel/module/internal.h
@@ -256,6 +256,11 @@ static inline bool sect_empty(const Elf_Shdr *sect)
static inline void init_build_id(struct module *mod, const struct load_info *info) { }
static inline void layout_symtab(struct module *mod, struct load_info *info) { }
static inline void add_kallsyms(struct module *mod, const struct load_info *info) { }
+static inline unsigned long find_kallsyms_symbol_value(struct module *mod
+ const char *name)
+{
+ return 0;
+}
#endif /* CONFIG_KALLSYMS */
#ifdef CONFIG_SYSFS
--
2.39.1
