From: Roberto Sassu roberto.sassu@huawei.com
Add the _opts variant for bpf_*_get_fd_by_id() functions, to be able to pass to the kernel more options, when requesting a fd of an eBPF object to the kernel.
Pass the options through a newly introduced structure, bpf_get_fd_opts, which currently contains open_flags (the other two members are for compatibility and for padding).
open_flags allows the caller to request specific permissions to access a map (e.g. read-only). This is useful for example in the situation where a map is write-protected.
Besides patches 2-6, which introduce the new variants and the data structure, patch 1 fixes the LIBBPF_1.0.0 declaration in libbpf.map.
Roberto Sassu (6): libbpf: Fix LIBBPF_1.0.0 declaration in libbpf.map libbpf: Define bpf_get_fd_opts and introduce bpf_map_get_fd_by_id_opts() libbpf: Introduce bpf_prog_get_fd_by_id_opts() libbpf: Introduce bpf_btf_get_fd_by_id_opts() libbpf: Introduce bpf_link_get_fd_by_id_opts() selftests/bpf: Add tests for _opts variants of bpf_*_get_fd_by_id()
tools/lib/bpf/bpf.c | 47 +++++++++- tools/lib/bpf/bpf.h | 16 ++++ tools/lib/bpf/libbpf.map | 6 +- .../bpf/prog_tests/libbpf_get_fd_opts.c | 88 +++++++++++++++++++ .../bpf/progs/test_libbpf_get_fd_opts.c | 36 ++++++++ 5 files changed, 188 insertions(+), 5 deletions(-) create mode 100644 tools/testing/selftests/bpf/prog_tests/libbpf_get_fd_opts.c create mode 100644 tools/testing/selftests/bpf/progs/test_libbpf_get_fd_opts.c
From: Roberto Sassu roberto.sassu@huawei.com
Add the missing LIBBPF_0.8.0 at the end of the LIBBPF_1.0.0 declaration, similarly to other version declarations.
Cc: stable@vger.kernel.org # 5.19.x Fixes: e2371b1632b1c ("libbpf: start 1.0 development cycle") Signed-off-by: Roberto Sassu roberto.sassu@huawei.com --- tools/lib/bpf/libbpf.map | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map index c1d6aa7c82b6..04fab9f1fdd7 100644 --- a/tools/lib/bpf/libbpf.map +++ b/tools/lib/bpf/libbpf.map @@ -367,7 +367,7 @@ LIBBPF_1.0.0 { libbpf_bpf_map_type_str; libbpf_bpf_prog_type_str; perf_buffer__buffer; -}; +} LIBBPF_0.8.0;
LIBBPF_1.1.0 { global:
From: Roberto Sassu roberto.sassu@huawei.com
Define a new data structure called bpf_get_fd_opts, with the member open_flags, to be used by callers of the _opts variants of bpf_*_get_fd_by_id() to specify the permissions needed for the file descriptor to be obtained.
Also, introduce bpf_map_get_fd_by_id_opts(), to let the caller pass a bpf_get_fd_opts structure.
Finally, keep the existing bpf_map_get_fd_by_id(), and call bpf_map_get_fd_by_id_opts() with NULL as opts argument, to request read-write permissions (current behavior).
Signed-off-by: Roberto Sassu roberto.sassu@huawei.com --- tools/lib/bpf/bpf.c | 12 +++++++++++- tools/lib/bpf/bpf.h | 10 ++++++++++ tools/lib/bpf/libbpf.map | 1 + 3 files changed, 22 insertions(+), 1 deletion(-)
diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c index 1d49a0352836..4b03063edf1d 100644 --- a/tools/lib/bpf/bpf.c +++ b/tools/lib/bpf/bpf.c @@ -948,19 +948,29 @@ int bpf_prog_get_fd_by_id(__u32 id) return libbpf_err_errno(fd); }
-int bpf_map_get_fd_by_id(__u32 id) +int bpf_map_get_fd_by_id_opts(__u32 id, + const struct bpf_get_fd_opts *opts) { const size_t attr_sz = offsetofend(union bpf_attr, open_flags); union bpf_attr attr; int fd;
+ if (!OPTS_VALID(opts, bpf_get_fd_opts)) + return libbpf_err(-EINVAL); + memset(&attr, 0, attr_sz); attr.map_id = id; + attr.open_flags = OPTS_GET(opts, open_flags, 0);
fd = sys_bpf_fd(BPF_MAP_GET_FD_BY_ID, &attr, attr_sz); return libbpf_err_errno(fd); }
+int bpf_map_get_fd_by_id(__u32 id) +{ + return bpf_map_get_fd_by_id_opts(id, NULL); +} + int bpf_btf_get_fd_by_id(__u32 id) { const size_t attr_sz = offsetofend(union bpf_attr, open_flags); diff --git a/tools/lib/bpf/bpf.h b/tools/lib/bpf/bpf.h index 9c50beabdd14..c60eda3c88ad 100644 --- a/tools/lib/bpf/bpf.h +++ b/tools/lib/bpf/bpf.h @@ -365,7 +365,17 @@ LIBBPF_API int bpf_prog_get_next_id(__u32 start_id, __u32 *next_id); LIBBPF_API int bpf_map_get_next_id(__u32 start_id, __u32 *next_id); LIBBPF_API int bpf_btf_get_next_id(__u32 start_id, __u32 *next_id); LIBBPF_API int bpf_link_get_next_id(__u32 start_id, __u32 *next_id); + +struct bpf_get_fd_opts { + size_t sz; /* size of this struct for forward/backward compatibility */ + __u32 open_flags; /* permissions requested for the operation on fd */ + size_t :0; +}; +#define bpf_get_fd_opts__last_field open_flags + LIBBPF_API int bpf_prog_get_fd_by_id(__u32 id); +LIBBPF_API int bpf_map_get_fd_by_id_opts(__u32 id, + const struct bpf_get_fd_opts *opts); LIBBPF_API int bpf_map_get_fd_by_id(__u32 id); LIBBPF_API int bpf_btf_get_fd_by_id(__u32 id); LIBBPF_API int bpf_link_get_fd_by_id(__u32 id); diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map index 04fab9f1fdd7..2e665b21d84f 100644 --- a/tools/lib/bpf/libbpf.map +++ b/tools/lib/bpf/libbpf.map @@ -371,6 +371,7 @@ LIBBPF_1.0.0 {
LIBBPF_1.1.0 { global: + bpf_map_get_fd_by_id_opts; user_ring_buffer__discard; user_ring_buffer__free; user_ring_buffer__new;
From: Roberto Sassu roberto.sassu@huawei.com
Introduce bpf_prog_get_fd_by_id_opts(), for symmetry with bpf_map_get_fd_by_id_opts(), to let the caller pass the newly introduced data structure bpf_get_fd_opts. Keep the existing bpf_prog_get_fd_by_id(), and call bpf_prog_get_fd_by_id_opts() with NULL as opts argument, to prevent setting open_flags.
Currently, the kernel does not support non-zero open_flags for bpf_prog_get_fd_by_id_opts(), and a call with them will result in an error returned by the bpf() system call. The caller should always pass zero open_flags.
Signed-off-by: Roberto Sassu roberto.sassu@huawei.com --- tools/lib/bpf/bpf.c | 11 ++++++++++- tools/lib/bpf/bpf.h | 2 ++ tools/lib/bpf/libbpf.map | 1 + 3 files changed, 13 insertions(+), 1 deletion(-)
diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c index 4b03063edf1d..92464c2d1da7 100644 --- a/tools/lib/bpf/bpf.c +++ b/tools/lib/bpf/bpf.c @@ -935,19 +935,28 @@ int bpf_link_get_next_id(__u32 start_id, __u32 *next_id) return bpf_obj_get_next_id(start_id, next_id, BPF_LINK_GET_NEXT_ID); }
-int bpf_prog_get_fd_by_id(__u32 id) +int bpf_prog_get_fd_by_id_opts(__u32 id, const struct bpf_get_fd_opts *opts) { const size_t attr_sz = offsetofend(union bpf_attr, open_flags); union bpf_attr attr; int fd;
+ if (!OPTS_VALID(opts, bpf_get_fd_opts)) + return libbpf_err(-EINVAL); + memset(&attr, 0, attr_sz); attr.prog_id = id; + attr.open_flags = OPTS_GET(opts, open_flags, 0);
fd = sys_bpf_fd(BPF_PROG_GET_FD_BY_ID, &attr, attr_sz); return libbpf_err_errno(fd); }
+int bpf_prog_get_fd_by_id(__u32 id) +{ + return bpf_prog_get_fd_by_id_opts(id, NULL); +} + int bpf_map_get_fd_by_id_opts(__u32 id, const struct bpf_get_fd_opts *opts) { diff --git a/tools/lib/bpf/bpf.h b/tools/lib/bpf/bpf.h index c60eda3c88ad..595d342fb7f9 100644 --- a/tools/lib/bpf/bpf.h +++ b/tools/lib/bpf/bpf.h @@ -373,6 +373,8 @@ struct bpf_get_fd_opts { }; #define bpf_get_fd_opts__last_field open_flags
+LIBBPF_API int bpf_prog_get_fd_by_id_opts(__u32 id, + const struct bpf_get_fd_opts *opts); LIBBPF_API int bpf_prog_get_fd_by_id(__u32 id); LIBBPF_API int bpf_map_get_fd_by_id_opts(__u32 id, const struct bpf_get_fd_opts *opts); diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map index 2e665b21d84f..c3604eaa220d 100644 --- a/tools/lib/bpf/libbpf.map +++ b/tools/lib/bpf/libbpf.map @@ -372,6 +372,7 @@ LIBBPF_1.0.0 { LIBBPF_1.1.0 { global: bpf_map_get_fd_by_id_opts; + bpf_prog_get_fd_by_id_opts; user_ring_buffer__discard; user_ring_buffer__free; user_ring_buffer__new;
From: Roberto Sassu roberto.sassu@huawei.com
Introduce bpf_btf_get_fd_by_id_opts(), for symmetry with bpf_map_get_fd_by_id_opts(), to let the caller pass the newly introduced data structure bpf_get_fd_opts. Keep the existing bpf_btf_get_fd_by_id(), and call bpf_btf_get_fd_by_id_opts() with NULL as opts argument, to prevent setting open_flags.
Currently, the kernel does not support non-zero open_flags for bpf_btf_get_fd_by_id_opts(), and a call with them will result in an error returned by the bpf() system call. The caller should always pass zero open_flags.
Signed-off-by: Roberto Sassu roberto.sassu@huawei.com --- tools/lib/bpf/bpf.c | 12 +++++++++++- tools/lib/bpf/bpf.h | 2 ++ tools/lib/bpf/libbpf.map | 1 + 3 files changed, 14 insertions(+), 1 deletion(-)
diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c index 92464c2d1da7..f43e8c8afbd3 100644 --- a/tools/lib/bpf/bpf.c +++ b/tools/lib/bpf/bpf.c @@ -980,19 +980,29 @@ int bpf_map_get_fd_by_id(__u32 id) return bpf_map_get_fd_by_id_opts(id, NULL); }
-int bpf_btf_get_fd_by_id(__u32 id) +int bpf_btf_get_fd_by_id_opts(__u32 id, + const struct bpf_get_fd_opts *opts) { const size_t attr_sz = offsetofend(union bpf_attr, open_flags); union bpf_attr attr; int fd;
+ if (!OPTS_VALID(opts, bpf_get_fd_opts)) + return libbpf_err(-EINVAL); + memset(&attr, 0, attr_sz); attr.btf_id = id; + attr.open_flags = OPTS_GET(opts, open_flags, 0);
fd = sys_bpf_fd(BPF_BTF_GET_FD_BY_ID, &attr, attr_sz); return libbpf_err_errno(fd); }
+int bpf_btf_get_fd_by_id(__u32 id) +{ + return bpf_btf_get_fd_by_id_opts(id, NULL); +} + int bpf_link_get_fd_by_id(__u32 id) { const size_t attr_sz = offsetofend(union bpf_attr, open_flags); diff --git a/tools/lib/bpf/bpf.h b/tools/lib/bpf/bpf.h index 595d342fb7f9..559af0b84299 100644 --- a/tools/lib/bpf/bpf.h +++ b/tools/lib/bpf/bpf.h @@ -379,6 +379,8 @@ LIBBPF_API int bpf_prog_get_fd_by_id(__u32 id); LIBBPF_API int bpf_map_get_fd_by_id_opts(__u32 id, const struct bpf_get_fd_opts *opts); LIBBPF_API int bpf_map_get_fd_by_id(__u32 id); +LIBBPF_API int bpf_btf_get_fd_by_id_opts(__u32 id, + const struct bpf_get_fd_opts *opts); LIBBPF_API int bpf_btf_get_fd_by_id(__u32 id); LIBBPF_API int bpf_link_get_fd_by_id(__u32 id); LIBBPF_API int bpf_obj_get_info_by_fd(int bpf_fd, void *info, __u32 *info_len); diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map index c3604eaa220d..7011d5eec67b 100644 --- a/tools/lib/bpf/libbpf.map +++ b/tools/lib/bpf/libbpf.map @@ -371,6 +371,7 @@ LIBBPF_1.0.0 {
LIBBPF_1.1.0 { global: + bpf_btf_get_fd_by_id_opts; bpf_map_get_fd_by_id_opts; bpf_prog_get_fd_by_id_opts; user_ring_buffer__discard;
From: Roberto Sassu roberto.sassu@huawei.com
Introduce bpf_link_get_fd_by_id_opts(), for symmetry with bpf_map_get_fd_by_id_opts(), to let the caller pass the newly introduced data structure bpf_get_fd_opts. Keep the existing bpf_link_get_fd_by_id(), and call bpf_link_get_fd_by_id_opts() with NULL as opts argument, to prevent setting open_flags.
Currently, the kernel does not support non-zero open_flags for bpf_link_get_fd_by_id_opts(), and a call with them will result in an error returned by the bpf() system call. The caller should always pass zero open_flags.
Signed-off-by: Roberto Sassu roberto.sassu@huawei.com --- tools/lib/bpf/bpf.c | 12 +++++++++++- tools/lib/bpf/bpf.h | 2 ++ tools/lib/bpf/libbpf.map | 1 + 3 files changed, 14 insertions(+), 1 deletion(-)
diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c index f43e8c8afbd3..f3d89a2bdb50 100644 --- a/tools/lib/bpf/bpf.c +++ b/tools/lib/bpf/bpf.c @@ -1003,19 +1003,29 @@ int bpf_btf_get_fd_by_id(__u32 id) return bpf_btf_get_fd_by_id_opts(id, NULL); }
-int bpf_link_get_fd_by_id(__u32 id) +int bpf_link_get_fd_by_id_opts(__u32 id, + const struct bpf_get_fd_opts *opts) { const size_t attr_sz = offsetofend(union bpf_attr, open_flags); union bpf_attr attr; int fd;
+ if (!OPTS_VALID(opts, bpf_get_fd_opts)) + return libbpf_err(-EINVAL); + memset(&attr, 0, attr_sz); attr.link_id = id; + attr.open_flags = OPTS_GET(opts, open_flags, 0);
fd = sys_bpf_fd(BPF_LINK_GET_FD_BY_ID, &attr, attr_sz); return libbpf_err_errno(fd); }
+int bpf_link_get_fd_by_id(__u32 id) +{ + return bpf_link_get_fd_by_id_opts(id, NULL); +} + int bpf_obj_get_info_by_fd(int bpf_fd, void *info, __u32 *info_len) { const size_t attr_sz = offsetofend(union bpf_attr, info); diff --git a/tools/lib/bpf/bpf.h b/tools/lib/bpf/bpf.h index 559af0b84299..834809d74c82 100644 --- a/tools/lib/bpf/bpf.h +++ b/tools/lib/bpf/bpf.h @@ -382,6 +382,8 @@ LIBBPF_API int bpf_map_get_fd_by_id(__u32 id); LIBBPF_API int bpf_btf_get_fd_by_id_opts(__u32 id, const struct bpf_get_fd_opts *opts); LIBBPF_API int bpf_btf_get_fd_by_id(__u32 id); +LIBBPF_API int bpf_link_get_fd_by_id_opts(__u32 id, + const struct bpf_get_fd_opts *opts); LIBBPF_API int bpf_link_get_fd_by_id(__u32 id); LIBBPF_API int bpf_obj_get_info_by_fd(int bpf_fd, void *info, __u32 *info_len);
diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map index 7011d5eec67b..71bf5691a689 100644 --- a/tools/lib/bpf/libbpf.map +++ b/tools/lib/bpf/libbpf.map @@ -372,6 +372,7 @@ LIBBPF_1.0.0 { LIBBPF_1.1.0 { global: bpf_btf_get_fd_by_id_opts; + bpf_link_get_fd_by_id_opts; bpf_map_get_fd_by_id_opts; bpf_prog_get_fd_by_id_opts; user_ring_buffer__discard;
From: Roberto Sassu roberto.sassu@huawei.com
Introduce the data_input map, write-protected with a small eBPF program implementing the lsm/bpf_map hook.
Then, ensure that bpf_map_get_fd_by_id() and bpf_map_get_fd_by_id_opts() with NULL opts don't succeed due to requesting read-write access to the write-protected map. Also, ensure that bpf_map_get_fd_by_id_opts() with open_flags in opts set to BPF_F_RDONLY instead succeeds.
After obtaining a read-only fd, ensure that only map lookup succeeds and not update. Ensure that update works only with the read-write fd obtained at program loading time, when the write protection was not yet enabled.
Finally, ensure that the other _opts variants of bpf_*_get_fd_by_id() don't work if the BPF_F_RDONLY flag is set in opts (due to the kernel not handling the open_flags member of bpf_attr).
Signed-off-by: Roberto Sassu roberto.sassu@huawei.com --- .../bpf/prog_tests/libbpf_get_fd_opts.c | 88 +++++++++++++++++++ .../bpf/progs/test_libbpf_get_fd_opts.c | 36 ++++++++ 2 files changed, 124 insertions(+) create mode 100644 tools/testing/selftests/bpf/prog_tests/libbpf_get_fd_opts.c create mode 100644 tools/testing/selftests/bpf/progs/test_libbpf_get_fd_opts.c
diff --git a/tools/testing/selftests/bpf/prog_tests/libbpf_get_fd_opts.c b/tools/testing/selftests/bpf/prog_tests/libbpf_get_fd_opts.c new file mode 100644 index 000000000000..2d4ba8f80d55 --- /dev/null +++ b/tools/testing/selftests/bpf/prog_tests/libbpf_get_fd_opts.c @@ -0,0 +1,88 @@ +// SPDX-License-Identifier: GPL-2.0 + +/* + * Copyright (C) 2022 Huawei Technologies Duesseldorf GmbH + * + * Author: Roberto Sassu roberto.sassu@huawei.com + */ + +#include <test_progs.h> + +#include "test_libbpf_get_fd_opts.skel.h" + +void test_libbpf_get_fd_opts(void) +{ + struct test_libbpf_get_fd_opts *skel; + struct bpf_map_info info_m = { 0 }; + __u32 len = sizeof(info_m), value; + struct bpf_map *map; + int ret, zero = 0, fd = -1; + + DECLARE_LIBBPF_OPTS(bpf_get_fd_opts, fd_opts_rdonly, + .open_flags = BPF_F_RDONLY, + ); + + skel = test_libbpf_get_fd_opts__open_and_load(); + if (!ASSERT_OK_PTR(skel, "test_libbpf_get_fd_opts__open_and_load")) + return; + + ret = test_libbpf_get_fd_opts__attach(skel); + if (!ASSERT_OK(ret, "test_libbpf_get_fd_opts__attach")) + goto close_prog; + + map = bpf_object__find_map_by_name(skel->obj, "data_input"); + if (!ASSERT_OK_PTR(map, "bpf_object__find_map_by_name")) + goto close_prog; + + ret = bpf_obj_get_info_by_fd(bpf_map__fd(map), &info_m, &len); + if (!ASSERT_OK(ret, "bpf_obj_get_info_by_fd")) + goto close_prog; + + fd = bpf_map_get_fd_by_id(info_m.id); + if (!ASSERT_LT(fd, 0, "bpf_map_get_fd_by_id")) + goto close_prog; + + fd = bpf_map_get_fd_by_id_opts(info_m.id, NULL); + if (!ASSERT_LT(fd, 0, "bpf_map_get_fd_by_id_opts")) + goto close_prog; + + fd = bpf_map_get_fd_by_id_opts(info_m.id, &fd_opts_rdonly); + if (!ASSERT_GE(fd, 0, "bpf_map_get_fd_by_id_opts")) + goto close_prog; + + /* Map lookup should work with read-only fd. */ + ret = bpf_map_lookup_elem(fd, &zero, &value); + if (!ASSERT_OK(ret, "bpf_map_lookup_elem")) + goto close_prog; + + if (!ASSERT_EQ(value, 0, "map value mismatch")) + goto close_prog; + + /* Map update should not work with read-only fd. */ + ret = bpf_map_update_elem(fd, &zero, &len, BPF_ANY); + if (!ASSERT_LT(ret, 0, "bpf_map_update_elem")) + goto close_prog; + + /* Map update should work with read-write fd. */ + ret = bpf_map_update_elem(bpf_map__fd(map), &zero, &len, BPF_ANY); + if (!ASSERT_OK(ret, "bpf_map_update_elem")) + goto close_prog; + + /* Prog get fd with opts set should not work (no kernel support). */ + ret = bpf_prog_get_fd_by_id_opts(0, &fd_opts_rdonly); + if (!ASSERT_EQ(ret, -EINVAL, "bpf_prog_get_fd_by_id_opts")) + goto close_prog; + + /* Link get fd with opts set should not work (no kernel support). */ + ret = bpf_link_get_fd_by_id_opts(0, &fd_opts_rdonly); + if (!ASSERT_EQ(ret, -EINVAL, "bpf_link_get_fd_by_id_opts")) + goto close_prog; + + /* BTF get fd with opts set should not work (no kernel support). */ + ret = bpf_btf_get_fd_by_id_opts(0, &fd_opts_rdonly); + ASSERT_EQ(ret, -EINVAL, "bpf_btf_get_fd_by_id_opts"); + +close_prog: + close(fd); + test_libbpf_get_fd_opts__destroy(skel); +} diff --git a/tools/testing/selftests/bpf/progs/test_libbpf_get_fd_opts.c b/tools/testing/selftests/bpf/progs/test_libbpf_get_fd_opts.c new file mode 100644 index 000000000000..f5ac5f3e8919 --- /dev/null +++ b/tools/testing/selftests/bpf/progs/test_libbpf_get_fd_opts.c @@ -0,0 +1,36 @@ +// SPDX-License-Identifier: GPL-2.0 + +/* + * Copyright (C) 2022 Huawei Technologies Duesseldorf GmbH + * + * Author: Roberto Sassu roberto.sassu@huawei.com + */ + +#include "vmlinux.h" +#include <errno.h> +#include <bpf/bpf_helpers.h> +#include <bpf/bpf_tracing.h> + +/* From include/linux/mm.h. */ +#define FMODE_WRITE 0x2 + +struct { + __uint(type, BPF_MAP_TYPE_ARRAY); + __uint(max_entries, 1); + __type(key, __u32); + __type(value, __u32); +} data_input SEC(".maps"); + +char _license[] SEC("license") = "GPL"; + +SEC("lsm/bpf_map") +int BPF_PROG(check_access, struct bpf_map *map, fmode_t fmode) +{ + if (map != (struct bpf_map *)&data_input) + return 0; + + if (fmode & FMODE_WRITE) + return -EACCES; + + return 0; +}
linux-kselftest-mirror@lists.linaro.org
-
Roberto Sassu