From 005142b8a1f0f32d33fbe04b728464c1b7acfa0e Mon Sep 17 00:00:00 2001 From: Alexei Starovoitov Date: Tue, 18 Aug 2020 21:27:56 -0700 Subject: [PATCH] bpf: Factor out bpf_link_by_id() helper. Refactor the code a bit to extract bpf_link_by_id() helper. It's similar to existing bpf_prog_by_id(). Signed-off-by: Alexei Starovoitov Signed-off-by: Daniel Borkmann Acked-by: Andrii Nakryiko Acked-by: Song Liu Link: https://lore.kernel.org/bpf/20200819042759.51280-2-alexei.starovoitov@gmail.com --- include/linux/bpf.h | 1 + kernel/bpf/syscall.c | 46 +++++++++++++++++++++++++++----------------- 2 files changed, 29 insertions(+), 18 deletions(-) diff --git a/include/linux/bpf.h b/include/linux/bpf.h index 55f694b63164..a9b7185a6b37 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -1358,6 +1358,7 @@ int btf_check_type_match(struct bpf_verifier_env *env, struct bpf_prog *prog, struct btf *btf, const struct btf_type *t); struct bpf_prog *bpf_prog_by_id(u32 id); +struct bpf_link *bpf_link_by_id(u32 id); const struct bpf_func_proto *bpf_base_func_proto(enum bpf_func_id func_id); #else /* !CONFIG_BPF_SYSCALL */ diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index 86299a292214..689d736b6904 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -4014,9 +4014,31 @@ static int link_detach(union bpf_attr *attr) return ret; } -static int bpf_link_inc_not_zero(struct bpf_link *link) +static struct bpf_link *bpf_link_inc_not_zero(struct bpf_link *link) { - return atomic64_fetch_add_unless(&link->refcnt, 1, 0) ? 0 : -ENOENT; + return atomic64_fetch_add_unless(&link->refcnt, 1, 0) ? link : ERR_PTR(-ENOENT); +} + +struct bpf_link *bpf_link_by_id(u32 id) +{ + struct bpf_link *link; + + if (!id) + return ERR_PTR(-ENOENT); + + spin_lock_bh(&link_idr_lock); + /* before link is "settled", ID is 0, pretend it doesn't exist yet */ + link = idr_find(&link_idr, id); + if (link) { + if (link->id) + link = bpf_link_inc_not_zero(link); + else + link = ERR_PTR(-EAGAIN); + } else { + link = ERR_PTR(-ENOENT); + } + spin_unlock_bh(&link_idr_lock); + return link; } #define BPF_LINK_GET_FD_BY_ID_LAST_FIELD link_id @@ -4025,7 +4047,7 @@ static int bpf_link_get_fd_by_id(const union bpf_attr *attr) { struct bpf_link *link; u32 id = attr->link_id; - int fd, err; + int fd; if (CHECK_ATTR(BPF_LINK_GET_FD_BY_ID)) return -EINVAL; @@ -4033,21 +4055,9 @@ static int bpf_link_get_fd_by_id(const union bpf_attr *attr) if (!capable(CAP_SYS_ADMIN)) return -EPERM; - spin_lock_bh(&link_idr_lock); - link = idr_find(&link_idr, id); - /* before link is "settled", ID is 0, pretend it doesn't exist yet */ - if (link) { - if (link->id) - err = bpf_link_inc_not_zero(link); - else - err = -EAGAIN; - } else { - err = -ENOENT; - } - spin_unlock_bh(&link_idr_lock); - - if (err) - return err; + link = bpf_link_by_id(id); + if (IS_ERR(link)) + return PTR_ERR(link); fd = bpf_link_new_fd(link); if (fd < 0)