提交 b16d9aa4 编写于 作者: M Martin KaFai Lau 提交者: David S. Miller

bpf: Add BPF_PROG_GET_FD_BY_ID

Add BPF_PROG_GET_FD_BY_ID command to allow user to get a fd
from a bpf_prog's ID.

bpf_prog_inc_not_zero() is added and is called with prog_idr_lock
held.

__bpf_prog_put() is also added which has the 'bool do_idr_lock'
param to decide if the prog_idr_lock should be acquired when
freeing the prog->id.

In the error path of bpf_prog_inc_not_zero(), it may have to
call __bpf_prog_put(map, false) which does not need
to take the prog_idr_lock when freeing the prog->id.

It is currently limited to CAP_SYS_ADMIN which we can
consider to lift it in followup patches.
Signed-off-by: NMartin KaFai Lau <kafai@fb.com>
Acked-by: NAlexei Starovoitov <ast@fb.com>
Acked-by: NDaniel Borkmann <daniel@iogearbox.net>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
上级 34ad5580
...@@ -84,6 +84,7 @@ enum bpf_cmd { ...@@ -84,6 +84,7 @@ enum bpf_cmd {
BPF_PROG_TEST_RUN, BPF_PROG_TEST_RUN,
BPF_PROG_GET_NEXT_ID, BPF_PROG_GET_NEXT_ID,
BPF_MAP_GET_NEXT_ID, BPF_MAP_GET_NEXT_ID,
BPF_PROG_GET_FD_BY_ID,
}; };
enum bpf_map_type { enum bpf_map_type {
...@@ -212,8 +213,11 @@ union bpf_attr { ...@@ -212,8 +213,11 @@ union bpf_attr {
__u32 duration; __u32 duration;
} test; } test;
struct { /* anonymous struct used by BPF_*_GET_NEXT_ID */ struct { /* anonymous struct used by BPF_*_GET_*_ID */
__u32 start_id; union {
__u32 start_id;
__u32 prog_id;
};
__u32 next_id; __u32 next_id;
}; };
} __attribute__((aligned(8))); } __attribute__((aligned(8)));
......
...@@ -703,15 +703,23 @@ static int bpf_prog_alloc_id(struct bpf_prog *prog) ...@@ -703,15 +703,23 @@ static int bpf_prog_alloc_id(struct bpf_prog *prog)
return id > 0 ? 0 : id; return id > 0 ? 0 : id;
} }
static void bpf_prog_free_id(struct bpf_prog *prog) static void bpf_prog_free_id(struct bpf_prog *prog, bool do_idr_lock)
{ {
/* cBPF to eBPF migrations are currently not in the idr store. */ /* cBPF to eBPF migrations are currently not in the idr store. */
if (!prog->aux->id) if (!prog->aux->id)
return; return;
spin_lock_bh(&prog_idr_lock); if (do_idr_lock)
spin_lock_bh(&prog_idr_lock);
else
__acquire(&prog_idr_lock);
idr_remove(&prog_idr, prog->aux->id); idr_remove(&prog_idr, prog->aux->id);
spin_unlock_bh(&prog_idr_lock);
if (do_idr_lock)
spin_unlock_bh(&prog_idr_lock);
else
__release(&prog_idr_lock);
} }
static void __bpf_prog_put_rcu(struct rcu_head *rcu) static void __bpf_prog_put_rcu(struct rcu_head *rcu)
...@@ -723,16 +731,21 @@ static void __bpf_prog_put_rcu(struct rcu_head *rcu) ...@@ -723,16 +731,21 @@ static void __bpf_prog_put_rcu(struct rcu_head *rcu)
bpf_prog_free(aux->prog); bpf_prog_free(aux->prog);
} }
void bpf_prog_put(struct bpf_prog *prog) static void __bpf_prog_put(struct bpf_prog *prog, bool do_idr_lock)
{ {
if (atomic_dec_and_test(&prog->aux->refcnt)) { if (atomic_dec_and_test(&prog->aux->refcnt)) {
trace_bpf_prog_put_rcu(prog); trace_bpf_prog_put_rcu(prog);
/* bpf_prog_free_id() must be called first */ /* bpf_prog_free_id() must be called first */
bpf_prog_free_id(prog); bpf_prog_free_id(prog, do_idr_lock);
bpf_prog_kallsyms_del(prog); bpf_prog_kallsyms_del(prog);
call_rcu(&prog->aux->rcu, __bpf_prog_put_rcu); call_rcu(&prog->aux->rcu, __bpf_prog_put_rcu);
} }
} }
void bpf_prog_put(struct bpf_prog *prog)
{
__bpf_prog_put(prog, true);
}
EXPORT_SYMBOL_GPL(bpf_prog_put); EXPORT_SYMBOL_GPL(bpf_prog_put);
static int bpf_prog_release(struct inode *inode, struct file *filp) static int bpf_prog_release(struct inode *inode, struct file *filp)
...@@ -814,6 +827,24 @@ struct bpf_prog *bpf_prog_inc(struct bpf_prog *prog) ...@@ -814,6 +827,24 @@ struct bpf_prog *bpf_prog_inc(struct bpf_prog *prog)
} }
EXPORT_SYMBOL_GPL(bpf_prog_inc); EXPORT_SYMBOL_GPL(bpf_prog_inc);
/* prog_idr_lock should have been held */
static struct bpf_prog *bpf_prog_inc_not_zero(struct bpf_prog *prog)
{
int refold;
refold = __atomic_add_unless(&prog->aux->refcnt, 1, 0);
if (refold >= BPF_MAX_REFCNT) {
__bpf_prog_put(prog, false);
return ERR_PTR(-EBUSY);
}
if (!refold)
return ERR_PTR(-ENOENT);
return prog;
}
static struct bpf_prog *__bpf_prog_get(u32 ufd, enum bpf_prog_type *type) static struct bpf_prog *__bpf_prog_get(u32 ufd, enum bpf_prog_type *type)
{ {
struct fd f = fdget(ufd); struct fd f = fdget(ufd);
...@@ -928,16 +959,21 @@ static int bpf_prog_load(union bpf_attr *attr) ...@@ -928,16 +959,21 @@ static int bpf_prog_load(union bpf_attr *attr)
goto free_used_maps; goto free_used_maps;
err = bpf_prog_new_fd(prog); err = bpf_prog_new_fd(prog);
if (err < 0) if (err < 0) {
/* failed to allocate fd */ /* failed to allocate fd.
goto free_id; * bpf_prog_put() is needed because the above
* bpf_prog_alloc_id() has published the prog
* to the userspace and the userspace may
* have refcnt-ed it through BPF_PROG_GET_FD_BY_ID.
*/
bpf_prog_put(prog);
return err;
}
bpf_prog_kallsyms_add(prog); bpf_prog_kallsyms_add(prog);
trace_bpf_prog_load(prog, err); trace_bpf_prog_load(prog, err);
return err; return err;
free_id:
bpf_prog_free_id(prog);
free_used_maps: free_used_maps:
free_used_maps(prog->aux); free_used_maps(prog->aux);
free_prog: free_prog:
...@@ -1099,6 +1135,38 @@ static int bpf_obj_get_next_id(const union bpf_attr *attr, ...@@ -1099,6 +1135,38 @@ static int bpf_obj_get_next_id(const union bpf_attr *attr,
return err; return err;
} }
#define BPF_PROG_GET_FD_BY_ID_LAST_FIELD prog_id
static int bpf_prog_get_fd_by_id(const union bpf_attr *attr)
{
struct bpf_prog *prog;
u32 id = attr->prog_id;
int fd;
if (CHECK_ATTR(BPF_PROG_GET_FD_BY_ID))
return -EINVAL;
if (!capable(CAP_SYS_ADMIN))
return -EPERM;
spin_lock_bh(&prog_idr_lock);
prog = idr_find(&prog_idr, id);
if (prog)
prog = bpf_prog_inc_not_zero(prog);
else
prog = ERR_PTR(-ENOENT);
spin_unlock_bh(&prog_idr_lock);
if (IS_ERR(prog))
return PTR_ERR(prog);
fd = bpf_prog_new_fd(prog);
if (fd < 0)
bpf_prog_put(prog);
return fd;
}
SYSCALL_DEFINE3(bpf, int, cmd, union bpf_attr __user *, uattr, unsigned int, size) SYSCALL_DEFINE3(bpf, int, cmd, union bpf_attr __user *, uattr, unsigned int, size)
{ {
union bpf_attr attr = {}; union bpf_attr attr = {};
...@@ -1184,6 +1252,9 @@ SYSCALL_DEFINE3(bpf, int, cmd, union bpf_attr __user *, uattr, unsigned int, siz ...@@ -1184,6 +1252,9 @@ SYSCALL_DEFINE3(bpf, int, cmd, union bpf_attr __user *, uattr, unsigned int, siz
err = bpf_obj_get_next_id(&attr, uattr, err = bpf_obj_get_next_id(&attr, uattr,
&map_idr, &map_idr_lock); &map_idr, &map_idr_lock);
break; break;
case BPF_PROG_GET_FD_BY_ID:
err = bpf_prog_get_fd_by_id(&attr);
break;
default: default:
err = -EINVAL; err = -EINVAL;
break; break;
......
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