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bpf: Add bpf_sys_close() helper.

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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 <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210514003623.28033-11-alexei.starovoitov@gmail.com
This commit is contained in:
Alexei Starovoitov
2021-05-13 17:36:12 -07:00
committed by Daniel Borkmann
parent 3d78417b60
commit 3abea08924
3 changed files with 33 additions and 0 deletions
Download Patch File Download Diff File Expand all files Collapse all files

7
include/uapi/linux/bpf.h
View File

@@ -4754,6 +4754,12 @@ union bpf_attr {
* Find BTF type with given name and kind in vmlinux BTF or in module's BTFs. * Find BTF type with given name and kind in vmlinux BTF or in module's BTFs.
* Return * Return
* Returns btf_id and btf_obj_fd in lower and upper 32 bits. * 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) \ #define __BPF_FUNC_MAPPER(FN) \
FN(unspec), \ FN(unspec), \
@@ -4924,6 +4930,7 @@ union bpf_attr {
FN(snprintf), \ FN(snprintf), \
FN(sys_bpf), \ FN(sys_bpf), \
FN(btf_find_by_name_kind), \ FN(btf_find_by_name_kind), \
FN(sys_close), \
/* */ /* */
/* integer value in 'imm' field of BPF_CALL instruction selects which helper /* integer value in 'imm' field of BPF_CALL instruction selects which helper

19
kernel/bpf/syscall.c
View File

@@ -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); 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 * static const struct bpf_func_proto *
syscall_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) 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; return &bpf_sys_bpf_proto;
case BPF_FUNC_btf_find_by_name_kind: case BPF_FUNC_btf_find_by_name_kind:
return &bpf_btf_find_by_name_kind_proto; return &bpf_btf_find_by_name_kind_proto;
case BPF_FUNC_sys_close:
return &bpf_sys_close_proto;
default: default:
return tracing_prog_func_proto(func_id, prog); return tracing_prog_func_proto(func_id, prog);
} }

7
tools/include/uapi/linux/bpf.h
View File

@@ -4754,6 +4754,12 @@ union bpf_attr {
* Find BTF type with given name and kind in vmlinux BTF or in module's BTFs. * Find BTF type with given name and kind in vmlinux BTF or in module's BTFs.
* Return * Return
* Returns btf_id and btf_obj_fd in lower and upper 32 bits. * 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) \ #define __BPF_FUNC_MAPPER(FN) \
FN(unspec), \ FN(unspec), \
@@ -4924,6 +4930,7 @@ union bpf_attr {
FN(snprintf), \ FN(snprintf), \
FN(sys_bpf), \ FN(sys_bpf), \
FN(btf_find_by_name_kind), \ FN(btf_find_by_name_kind), \
FN(sys_close), \
/* */ /* */
/* integer value in 'imm' field of BPF_CALL instruction selects which helper /* integer value in 'imm' field of BPF_CALL instruction selects which helper