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bpf: Make every prog keep a copy of ctx_arg_info

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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>
This commit is contained in:
Amery Hung 2025-02-17 11:06:36 -08:00 committed by Alexei Starovoitov
parent 4eb93fea59
commit 432051806f
4 changed files with 24 additions and 19 deletions
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7
include/linux/bpf.h
View File

@ -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);

13
kernel/bpf/bpf_iter.c
View File

@ -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 *

1
kernel/bpf/syscall.c
View File

@ -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);

22
kernel/bpf/verifier.c
View File

@ -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) {