bpf: Make every prog keep a copy of ctx_arg_info

Currently, ctx_arg_info is read-only in the view of the verifier since
it is shared among programs of the same attach type. Make each program
have their own copy of ctx_arg_info so that we can use it to store
program specific information.

In the next patch where we support acquiring a referenced kptr through a
struct_ops argument tagged with "__ref", ctx_arg_info->ref_obj_id will
be used to store the unique reference object id of the argument. This
avoids creating a requirement in the verifier that "__ref" tagged
arguments must be the first set of references acquired [0].

[0] https://lore.kernel.org/bpf/20241220195619.2022866-2-amery.hung@gmail.com/

Signed-off-by: Amery Hung <ameryhung@gmail.com>
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Acked-by: Martin KaFai Lau <martin.lau@kernel.org>
Link: https://lore.kernel.org/r/20250217190640.1748177-2-ameryhung@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index f3f50e29d63929acaf12c81f8356173f1f5e154b..f4df39e8c7357b5a92ad3c8aedfa1cff5c49af16 100644 (file)
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1507,7 +1507,7 @@ struct bpf_prog_aux {
        u32 max_rdonly_access;
        u32 max_rdwr_access;
        struct btf *attach_btf;
-       const struct bpf_ctx_arg_aux *ctx_arg_info;
+       struct bpf_ctx_arg_aux *ctx_arg_info;
        void __percpu *priv_stack_ptr;
        struct mutex dst_mutex; /* protects dst_* pointers below, *after* prog becomes visible */
        struct bpf_prog *dst_prog;
@@ -1945,6 +1945,9 @@ static inline void bpf_struct_ops_desc_release(struct bpf_struct_ops_desc *st_op
 
 #endif
 
+int bpf_prog_ctx_arg_info_init(struct bpf_prog *prog,
+                              const struct bpf_ctx_arg_aux *info, u32 cnt);
+
 #if defined(CONFIG_CGROUP_BPF) && defined(CONFIG_BPF_LSM)
 int bpf_trampoline_link_cgroup_shim(struct bpf_prog *prog,
                                    int cgroup_atype);
@@ -2546,7 +2549,7 @@ struct bpf_iter__bpf_map_elem {
 
 int bpf_iter_reg_target(const struct bpf_iter_reg *reg_info);
 void bpf_iter_unreg_target(const struct bpf_iter_reg *reg_info);
-bool bpf_iter_prog_supported(struct bpf_prog *prog);
+int bpf_iter_prog_supported(struct bpf_prog *prog);
 const struct bpf_func_proto *
 bpf_iter_get_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog);
 int bpf_iter_link_attach(const union bpf_attr *attr, bpfptr_t uattr, struct bpf_prog *prog);

diff --git a/kernel/bpf/bpf_iter.c b/kernel/bpf/bpf_iter.c
index 106735145948b4871e643dbe8b404e4c6b8c30c4..380e9a7cac75da61fed04710918bf341c79e3aab 100644 (file)
--- a/kernel/bpf/bpf_iter.c
+++ b/kernel/bpf/bpf_iter.c
@@ -335,7 +335,7 @@ static void cache_btf_id(struct bpf_iter_target_info *tinfo,
        tinfo->btf_id = prog->aux->attach_btf_id;
 }
 
-bool bpf_iter_prog_supported(struct bpf_prog *prog)
+int bpf_iter_prog_supported(struct bpf_prog *prog)
 {
        const char *attach_fname = prog->aux->attach_func_name;
        struct bpf_iter_target_info *tinfo = NULL, *iter;
@@ -344,7 +344,7 @@ bool bpf_iter_prog_supported(struct bpf_prog *prog)
        int prefix_len = strlen(prefix);
 
        if (strncmp(attach_fname, prefix, prefix_len))
-               return false;
+               return -EINVAL;
 
        mutex_lock(&targets_mutex);
        list_for_each_entry(iter, &targets, list) {
@@ -360,12 +360,11 @@ bool bpf_iter_prog_supported(struct bpf_prog *prog)
        }
        mutex_unlock(&targets_mutex);
 
-       if (tinfo) {
-               prog->aux->ctx_arg_info_size = tinfo->reg_info->ctx_arg_info_size;
-               prog->aux->ctx_arg_info = tinfo->reg_info->ctx_arg_info;
-       }
+       if (!tinfo)
+               return -EINVAL;
 
-       return tinfo != NULL;
+       return bpf_prog_ctx_arg_info_init(prog, tinfo->reg_info->ctx_arg_info,
+                                         tinfo->reg_info->ctx_arg_info_size);
 }
 
 const struct bpf_func_proto *

diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index c420edbfb7c874ddc5f0ba97d120b16c4ee81c02..4b89a5df8ebcb3b824325f06c81bba2b90e98f79 100644 (file)
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -2313,6 +2313,7 @@ static void __bpf_prog_put_noref(struct bpf_prog *prog, bool deferred)
        kvfree(prog->aux->jited_linfo);
        kvfree(prog->aux->linfo);
        kfree(prog->aux->kfunc_tab);
+       kfree(prog->aux->ctx_arg_info);
        if (prog->aux->attach_btf)
                btf_put(prog->aux->attach_btf);
 

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 3c286ec9e8413d7c7c7aa94937f4d99214c56430..a231223d985b41d817eb82dfe8da60e9173635cb 100644 (file)
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -22405,6 +22405,15 @@ static void print_verification_stats(struct bpf_verifier_env *env)
                env->peak_states, env->longest_mark_read_walk);
 }
 
+int bpf_prog_ctx_arg_info_init(struct bpf_prog *prog,
+                              const struct bpf_ctx_arg_aux *info, u32 cnt)
+{
+       prog->aux->ctx_arg_info = kmemdup_array(info, cnt, sizeof(*info), GFP_KERNEL);
+       prog->aux->ctx_arg_info_size = cnt;
+
+       return prog->aux->ctx_arg_info ? 0 : -ENOMEM;
+}
+
 static int check_struct_ops_btf_id(struct bpf_verifier_env *env)
 {
        const struct btf_type *t, *func_proto;
@@ -22485,17 +22494,12 @@ static int check_struct_ops_btf_id(struct bpf_verifier_env *env)
                return -EACCES;
        }
 
-       /* btf_ctx_access() used this to provide argument type info */
-       prog->aux->ctx_arg_info =
-               st_ops_desc->arg_info[member_idx].info;
-       prog->aux->ctx_arg_info_size =
-               st_ops_desc->arg_info[member_idx].cnt;
-
        prog->aux->attach_func_proto = func_proto;
        prog->aux->attach_func_name = mname;
        env->ops = st_ops->verifier_ops;
 
-       return 0;
+       return bpf_prog_ctx_arg_info_init(prog, st_ops_desc->arg_info[member_idx].info,
+                                         st_ops_desc->arg_info[member_idx].cnt);
 }
 #define SECURITY_PREFIX "security_"
 
@@ -22945,9 +22949,7 @@ static int check_attach_btf_id(struct bpf_verifier_env *env)
                prog->aux->attach_btf_trace = true;
                return 0;
        } else if (prog->expected_attach_type == BPF_TRACE_ITER) {
-               if (!bpf_iter_prog_supported(prog))
-                       return -EINVAL;
-               return 0;
+               return bpf_iter_prog_supported(prog);
        }
 
        if (prog->type == BPF_PROG_TYPE_LSM) {