Commit 3abea089 authored by Alexei Starovoitov's avatar Alexei Starovoitov Committed by Daniel Borkmann
Browse files

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: default avatarAlexei Starovoitov <ast@kernel.org>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Acked-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210514003623.28033-11-alexei.starovoitov@gmail.com
parent 3d78417b

include/uapi/linux/bpf.h

+7 −0
Original line number Diff line number Diff line
@@ -4754,6 +4754,12 @@ union bpf_attr { 
 * 		Find BTF type with given name and kind in vmlinux BTF or in module's BTFs.

 * 	Return

 * 		Returns btf_id and btf_obj_fd in lower and upper 32 bits.

 *

 * long bpf_sys_close(u32 fd)

 * 	Description

 * 		Execute close syscall for given FD.

 * 	Return

 * 		A syscall result.

 */

#define __BPF_FUNC_MAPPER(FN)		\

	FN(unspec),			\
@@ -4924,6 +4930,7 @@ union bpf_attr { 
	FN(snprintf),			\

	FN(sys_bpf),			\

	FN(btf_find_by_name_kind),	\

	FN(sys_close),			\

	/* */



/* integer value in 'imm' field of BPF_CALL instruction selects which helper

kernel/bpf/syscall.c

+19 −0
Original line number Diff line number Diff line
@@ -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);

	}

tools/include/uapi/linux/bpf.h

+7 −0
Original line number Diff line number Diff line
@@ -4754,6 +4754,12 @@ union bpf_attr { 
 * 		Find BTF type with given name and kind in vmlinux BTF or in module's BTFs.

 * 	Return

 * 		Returns btf_id and btf_obj_fd in lower and upper 32 bits.

 *

 * long bpf_sys_close(u32 fd)

 * 	Description

 * 		Execute close syscall for given FD.

 * 	Return

 * 		A syscall result.

 */

#define __BPF_FUNC_MAPPER(FN)		\

	FN(unspec),			\
@@ -4924,6 +4930,7 @@ union bpf_attr { 
	FN(snprintf),			\

	FN(sys_bpf),			\

	FN(btf_find_by_name_kind),	\

	FN(sys_close),			\

	/* */



/* integer value in 'imm' field of BPF_CALL instruction selects which helper