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bpf: add plumbing for file-backed dynptr

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Add the necessary verifier plumbing for the new file-backed dynptr type.
Introduce two kfuncs for its lifecycle management:
 * bpf_dynptr_from_file() for initialization
 * bpf_dynptr_file_discard() for destruction

Currently there is no mechanism for kfunc to release dynptr, this patch
add one:
 * Dynptr release function sets meta->release_regno
 * Call unmark_stack_slots_dynptr() if meta->release_regno is set and
 dynptr ref_obj_id is set as well.

Signed-off-by: Mykyta Yatsenko <yatsenko@meta.com>
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20251026203853.135105-7-mykyta.yatsenko5@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Mykyta Yatsenko 2025-10-26 20:38:49 +00:00 committed by Alexei Starovoitov
parent 9cba966f1c
commit 8d8771dc03
4 changed files with 45 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

7
include/linux/bpf.h
View File

@ -792,12 +792,15 @@ enum bpf_type_flag {
/* DYNPTR points to skb_metadata_end()-skb_metadata_len() */
DYNPTR_TYPE_SKB_META = BIT(19 + BPF_BASE_TYPE_BITS),
/* DYNPTR points to file */
DYNPTR_TYPE_FILE = BIT(20 + BPF_BASE_TYPE_BITS),
__BPF_TYPE_FLAG_MAX,
__BPF_TYPE_LAST_FLAG = __BPF_TYPE_FLAG_MAX - 1,
};
#define DYNPTR_TYPE_FLAG_MASK (DYNPTR_TYPE_LOCAL | DYNPTR_TYPE_RINGBUF | DYNPTR_TYPE_SKB \
| DYNPTR_TYPE_XDP | DYNPTR_TYPE_SKB_META)
| DYNPTR_TYPE_XDP | DYNPTR_TYPE_SKB_META | DYNPTR_TYPE_FILE)
/* Max number of base types. */
#define BPF_BASE_TYPE_LIMIT (1UL << BPF_BASE_TYPE_BITS)
@ -1385,6 +1388,8 @@ enum bpf_dynptr_type {
BPF_DYNPTR_TYPE_XDP,
/* Points to skb_metadata_end()-skb_metadata_len() */
BPF_DYNPTR_TYPE_SKB_META,
/* Underlying data is a file */
BPF_DYNPTR_TYPE_FILE,
};
int bpf_dynptr_check_size(u64 size);

12
kernel/bpf/helpers.c
View File

@ -4252,6 +4252,16 @@ __bpf_kfunc int bpf_task_work_schedule_resume(struct task_struct *task, struct b
return bpf_task_work_schedule(task, tw, map__map, callback, aux__prog, TWA_RESUME);
}
__bpf_kfunc int bpf_dynptr_from_file(struct file *file, u32 flags, struct bpf_dynptr *ptr__uninit)
{
return 0;
}
__bpf_kfunc int bpf_dynptr_file_discard(struct bpf_dynptr *dynptr)
{
return 0;
}
__bpf_kfunc_end_defs();
static void bpf_task_work_cancel_scheduled(struct irq_work *irq_work)
@ -4429,6 +4439,8 @@ BTF_ID_FLAGS(func, bpf_cgroup_read_xattr, KF_RCU)
BTF_ID_FLAGS(func, bpf_stream_vprintk, KF_TRUSTED_ARGS)
BTF_ID_FLAGS(func, bpf_task_work_schedule_signal, KF_TRUSTED_ARGS)
BTF_ID_FLAGS(func, bpf_task_work_schedule_resume, KF_TRUSTED_ARGS)
BTF_ID_FLAGS(func, bpf_dynptr_from_file, KF_TRUSTED_ARGS)
BTF_ID_FLAGS(func, bpf_dynptr_file_discard)
BTF_KFUNCS_END(common_btf_ids)
static const struct btf_kfunc_id_set common_kfunc_set = {

2
kernel/bpf/log.c
View File

@ -500,6 +500,8 @@ const char *dynptr_type_str(enum bpf_dynptr_type type)
return "xdp";
case BPF_DYNPTR_TYPE_SKB_META:
return "skb_meta";
case BPF_DYNPTR_TYPE_FILE:
return "file";
case BPF_DYNPTR_TYPE_INVALID:
return "<invalid>";
default:

31
kernel/bpf/verifier.c
View File

@ -692,6 +692,8 @@ static enum bpf_dynptr_type arg_to_dynptr_type(enum bpf_arg_type arg_type)
return BPF_DYNPTR_TYPE_XDP;
case DYNPTR_TYPE_SKB_META:
return BPF_DYNPTR_TYPE_SKB_META;
case DYNPTR_TYPE_FILE:
return BPF_DYNPTR_TYPE_FILE;
default:
return BPF_DYNPTR_TYPE_INVALID;
}
@ -710,6 +712,8 @@ static enum bpf_type_flag get_dynptr_type_flag(enum bpf_dynptr_type type)
return DYNPTR_TYPE_XDP;
case BPF_DYNPTR_TYPE_SKB_META:
return DYNPTR_TYPE_SKB_META;
case BPF_DYNPTR_TYPE_FILE:
return DYNPTR_TYPE_FILE;
default:
return 0;
}
@ -717,7 +721,7 @@ static enum bpf_type_flag get_dynptr_type_flag(enum bpf_dynptr_type type)
static bool dynptr_type_refcounted(enum bpf_dynptr_type type)
{
return type == BPF_DYNPTR_TYPE_RINGBUF;
return type == BPF_DYNPTR_TYPE_RINGBUF || type == BPF_DYNPTR_TYPE_FILE;
}
static void __mark_dynptr_reg(struct bpf_reg_state *reg,
@ -12291,6 +12295,8 @@ enum special_kfunc_type {
KF_bpf_res_spin_unlock,
KF_bpf_res_spin_lock_irqsave,
KF_bpf_res_spin_unlock_irqrestore,
KF_bpf_dynptr_from_file,
KF_bpf_dynptr_file_discard,
KF___bpf_trap,
KF_bpf_task_work_schedule_signal,
KF_bpf_task_work_schedule_resume,
@ -12363,6 +12369,8 @@ BTF_ID(func, bpf_res_spin_lock)
BTF_ID(func, bpf_res_spin_unlock)
BTF_ID(func, bpf_res_spin_lock_irqsave)
BTF_ID(func, bpf_res_spin_unlock_irqrestore)
BTF_ID(func, bpf_dynptr_from_file)
BTF_ID(func, bpf_dynptr_file_discard)
BTF_ID(func, __bpf_trap)
BTF_ID(func, bpf_task_work_schedule_signal)
BTF_ID(func, bpf_task_work_schedule_resume)
@ -13326,6 +13334,11 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_
dynptr_arg_type |= DYNPTR_TYPE_XDP;
} else if (meta->func_id == special_kfunc_list[KF_bpf_dynptr_from_skb_meta]) {
dynptr_arg_type |= DYNPTR_TYPE_SKB_META;
} else if (meta->func_id == special_kfunc_list[KF_bpf_dynptr_from_file]) {
dynptr_arg_type |= DYNPTR_TYPE_FILE;
} else if (meta->func_id == special_kfunc_list[KF_bpf_dynptr_file_discard]) {
dynptr_arg_type |= DYNPTR_TYPE_FILE;
meta->release_regno = regno;
} else if (meta->func_id == special_kfunc_list[KF_bpf_dynptr_clone] &&
(dynptr_arg_type & MEM_UNINIT)) {
enum bpf_dynptr_type parent_type = meta->initialized_dynptr.type;
@ -14006,12 +14019,18 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
* PTR_TO_BTF_ID in bpf_kfunc_arg_meta, do the release now.
*/
if (meta.release_regno) {
err = release_reference(env, regs[meta.release_regno].ref_obj_id);
if (err) {
verbose(env, "kfunc %s#%d reference has not been acquired before\n",
func_name, meta.func_id);
return err;
struct bpf_reg_state *reg = &regs[meta.release_regno];
if (meta.initialized_dynptr.ref_obj_id) {
err = unmark_stack_slots_dynptr(env, reg);
} else {
err = release_reference(env, reg->ref_obj_id);
if (err)
verbose(env, "kfunc %s#%d reference has not been acquired before\n",
func_name, meta.func_id);
}
if (err)
return err;
}
if (meta.func_id == special_kfunc_list[KF_bpf_list_push_front_impl] ||