From 3abea089246f76c1517b054ddb5946f3f1dbd2c0 Mon Sep 17 00:00:00 2001 From: Alexei Starovoitov Date: Thu, 13 May 2021 17:36:12 -0700 Subject: bpf: Add bpf_sys_close() helper. Add bpf_sys_close() helper to be used by the syscall/loader program to close intermediate FDs and other cleanup. Note this helper must never be allowed inside fdget/fdput bracketing. Signed-off-by: Alexei Starovoitov Signed-off-by: Daniel Borkmann Acked-by: Andrii Nakryiko Link: https://lore.kernel.org/bpf/20210514003623.28033-11-alexei.starovoitov@gmail.com --- kernel/bpf/syscall.c | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+) (limited to 'kernel') diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index f93ff2ebf96d..0f1ce2171f1e 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -4578,6 +4578,23 @@ tracing_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) return bpf_base_func_proto(func_id); } +BPF_CALL_1(bpf_sys_close, u32, fd) +{ + /* When bpf program calls this helper there should not be + * an fdget() without matching completed fdput(). + * This helper is allowed in the following callchain only: + * sys_bpf->prog_test_run->bpf_prog->bpf_sys_close + */ + return close_fd(fd); +} + +const struct bpf_func_proto bpf_sys_close_proto = { + .func = bpf_sys_close, + .gpl_only = false, + .ret_type = RET_INTEGER, + .arg1_type = ARG_ANYTHING, +}; + static const struct bpf_func_proto * syscall_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) { @@ -4586,6 +4603,8 @@ syscall_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) return &bpf_sys_bpf_proto; case BPF_FUNC_btf_find_by_name_kind: return &bpf_btf_find_by_name_kind_proto; + case BPF_FUNC_sys_close: + return &bpf_sys_close_proto; default: return tracing_prog_func_proto(func_id, prog); } -- cgit v1.2.3