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
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
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
>
