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bpf: Introduce bpf_map ID
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This patch generates an unique ID for each created bpf_map.
The approach is similar to the earlier patch for bpf_prog ID.

It is worth to note that the bpf_map's ID and bpf_prog's ID
are in two independent ID spaces and both have the same valid range:
[1, INT_MAX).

Signed-off-by: Martin KaFai Lau <[email protected]>
Acked-by: Alexei Starovoitov <[email protected]>
Acked-by: Daniel Borkmann <[email protected]>
Signed-off-by: David S. Miller <[email protected]>
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iamkafai authored and davem330 committed Jun 6, 2017
1 parent dc4bb0e commit f3f1c05
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Showing 2 changed files with 34 additions and 1 deletion.
1 change: 1 addition & 0 deletions include/linux/bpf.h
Original file line number Diff line number Diff line change
Expand Up @@ -46,6 +46,7 @@ struct bpf_map {
u32 max_entries;
u32 map_flags;
u32 pages;
u32 id;
struct user_struct *user;
const struct bpf_map_ops *ops;
struct work_struct work;
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34 changes: 33 additions & 1 deletion kernel/bpf/syscall.c
Original file line number Diff line number Diff line change
Expand Up @@ -27,6 +27,8 @@
DEFINE_PER_CPU(int, bpf_prog_active);
static DEFINE_IDR(prog_idr);
static DEFINE_SPINLOCK(prog_idr_lock);
static DEFINE_IDR(map_idr);
static DEFINE_SPINLOCK(map_idr_lock);

int sysctl_unprivileged_bpf_disabled __read_mostly;

Expand Down Expand Up @@ -117,6 +119,29 @@ static void bpf_map_uncharge_memlock(struct bpf_map *map)
free_uid(user);
}

static int bpf_map_alloc_id(struct bpf_map *map)
{
int id;

spin_lock_bh(&map_idr_lock);
id = idr_alloc_cyclic(&map_idr, map, 1, INT_MAX, GFP_ATOMIC);
if (id > 0)
map->id = id;
spin_unlock_bh(&map_idr_lock);

if (WARN_ON_ONCE(!id))
return -ENOSPC;

return id > 0 ? 0 : id;
}

static void bpf_map_free_id(struct bpf_map *map)
{
spin_lock_bh(&map_idr_lock);
idr_remove(&map_idr, map->id);
spin_unlock_bh(&map_idr_lock);
}

/* called from workqueue */
static void bpf_map_free_deferred(struct work_struct *work)
{
Expand All @@ -141,6 +166,7 @@ static void bpf_map_put_uref(struct bpf_map *map)
void bpf_map_put(struct bpf_map *map)
{
if (atomic_dec_and_test(&map->refcnt)) {
bpf_map_free_id(map);
INIT_WORK(&map->work, bpf_map_free_deferred);
schedule_work(&map->work);
}
Expand Down Expand Up @@ -239,14 +265,20 @@ static int map_create(union bpf_attr *attr)
if (err)
goto free_map_nouncharge;

err = bpf_map_alloc_id(map);
if (err)
goto free_map;

err = bpf_map_new_fd(map);
if (err < 0)
/* failed to allocate fd */
goto free_map;
goto free_id;

trace_bpf_map_create(map, err);
return err;

free_id:
bpf_map_free_id(map);
free_map:
bpf_map_uncharge_memlock(map);
free_map_nouncharge:
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