Commit dc4bb0e2 authored by Martin KaFai Lau's avatar Martin KaFai Lau Committed by David S. Miller
Browse files

bpf: Introduce bpf_prog ID 



This patch generates an unique ID for each BPF_PROG_LOAD-ed prog.
It is worth to note that each BPF_PROG_LOAD-ed prog will have
a different ID even they have the same bpf instructions.

The ID is generated by the existing idr_alloc_cyclic().
The ID is ranged from [1, INT_MAX).  It is allocated in cyclic manner,
so an ID will get reused every 2 billion BPF_PROG_LOAD.

The bpf_prog_alloc_id() is done after bpf_prog_select_runtime()
because the jit process may have allocated a new prog.  Hence,
we need to ensure the value of pointer 'prog' will not be changed
any more before storing the prog to the prog_idr.

After bpf_prog_select_runtime(), the prog is read-only.  Hence,
the id is stored in 'struct bpf_prog_aux'.

Signed-off-by: default avatarMartin KaFai Lau <kafai@fb.com>
Acked-by: default avatarAlexei Starovoitov <ast@fb.com>
Acked-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 8ea4fae9

include/linux/bpf.h

+1 −0
Original line number Diff line number Diff line
@@ -172,6 +172,7 @@ struct bpf_prog_aux { 
	u32 used_map_cnt;

	u32 max_ctx_offset;

	u32 stack_depth;

	u32 id;

	struct latch_tree_node ksym_tnode;

	struct list_head ksym_lnode;

	const struct bpf_verifier_ops *ops;

kernel/bpf/syscall.c

+39 −1
Original line number Diff line number Diff line
@@ -22,8 +22,11 @@ 
#include <linux/filter.h>

#include <linux/version.h>

#include <linux/kernel.h>

#include <linux/idr.h>



DEFINE_PER_CPU(int, bpf_prog_active);

static DEFINE_IDR(prog_idr);

static DEFINE_SPINLOCK(prog_idr_lock);



int sysctl_unprivileged_bpf_disabled __read_mostly;
@@ -650,6 +653,34 @@ static void bpf_prog_uncharge_memlock(struct bpf_prog *prog) 
	free_uid(user);

}



static int bpf_prog_alloc_id(struct bpf_prog *prog)

{

	int id;



	spin_lock_bh(&prog_idr_lock);

	id = idr_alloc_cyclic(&prog_idr, prog, 1, INT_MAX, GFP_ATOMIC);

	if (id > 0)

		prog->aux->id = id;

	spin_unlock_bh(&prog_idr_lock);



	/* id is in [1, INT_MAX) */

	if (WARN_ON_ONCE(!id))

		return -ENOSPC;



	return id > 0 ? 0 : id;

}



static void bpf_prog_free_id(struct bpf_prog *prog)

{

	/* cBPF to eBPF migrations are currently not in the idr store. */

	if (!prog->aux->id)

		return;



	spin_lock_bh(&prog_idr_lock);

	idr_remove(&prog_idr, prog->aux->id);

	spin_unlock_bh(&prog_idr_lock);

}



static void __bpf_prog_put_rcu(struct rcu_head *rcu)

{

	struct bpf_prog_aux *aux = container_of(rcu, struct bpf_prog_aux, rcu);
@@ -663,6 +694,7 @@ void bpf_prog_put(struct bpf_prog *prog) 
{

	if (atomic_dec_and_test(&prog->aux->refcnt)) {

		trace_bpf_prog_put_rcu(prog);

		bpf_prog_free_id(prog);

		bpf_prog_kallsyms_del(prog);

		call_rcu(&prog->aux->rcu, __bpf_prog_put_rcu);

	}
@@ -857,15 +889,21 @@ static int bpf_prog_load(union bpf_attr *attr) 
	if (err < 0)

		goto free_used_maps;



	err = bpf_prog_alloc_id(prog);

	if (err)

		goto free_used_maps;



	err = bpf_prog_new_fd(prog);

	if (err < 0)

		/* failed to allocate fd */

		goto free_used_maps;

		goto free_id;



	bpf_prog_kallsyms_add(prog);

	trace_bpf_prog_load(prog, err);

	return err;



free_id:

	bpf_prog_free_id(prog);

free_used_maps:

	free_used_maps(prog->aux);

free_prog:

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