Modify several functions in tools/bpf/bpftool/common.c to allow specification of requested access for file descriptors, such as read-only access.

Update bpftool to request only read access for maps when write access is not required. This fixes errors when reading from maps that are protected from modification via security_bpf_map.

Signed-off-by: Slava Imameev slava.imameev@crowdstrike.com --- Changes in v2: - fix for a test compilation error: "conflicting types for 'bpf_fentry_test1'" Changes in v3: - Addressed review feedback - Converted the check for flags to an assert in map_parse_fds - Modified map_fd_by_name to keep an existing fd where possible - Fixed requested access for map delete command in do_delete - Changed requested access to RDONLY for inner map fd in do_create - Changed requested access to RDONLY for iterator fd in do_pin Changes in v4: - Explicitly included assert.h in common.c - Added read only access to map in build_btf_type_table ---

tools/bpf/bpftool/btf.c --- tools/bpf/bpftool/btf.c | 8 +++-- tools/bpf/bpftool/common.c | 59 ++++++++++++++++++++++--------- tools/bpf/bpftool/iter.c | 2 +- tools/bpf/bpftool/link.c | 2 +- tools/bpf/bpftool/main.h | 13 ++++--- tools/bpf/bpftool/map.c | 56 +++++++++++++++++------------ tools/bpf/bpftool/map_perf_ring.c | 3 +- tools/bpf/bpftool/prog.c | 4 +-- 8 files changed, 96 insertions(+), 51 deletions(-)

diff --git a/tools/bpf/bpftool/btf.c b/tools/bpf/bpftool/btf.c index 6b14cbfa58aa..946612029dee 100644 --- a/tools/bpf/bpftool/btf.c +++ b/tools/bpf/bpftool/btf.c @@ -905,7 +905,8 @@ static int do_dump(int argc, char **argv) return -1; }

- fd = map_parse_fd_and_info(&argc, &argv, &info, &len); + fd = map_parse_fd_and_info(&argc, &argv, &info, &len, + BPF_F_RDONLY); if (fd < 0) return -1;

@@ -1118,10 +1119,13 @@ build_btf_type_table(struct hashmap *tab, enum bpf_obj_type type, [BPF_OBJ_PROG] = "prog", [BPF_OBJ_MAP] = "map", }; + LIBBPF_OPTS(bpf_get_fd_by_id_opts, opts_ro); __u32 btf_id, id = 0; int err; int fd;

+ opts_ro.open_flags = BPF_F_RDONLY; + while (true) { switch (type) { case BPF_OBJ_PROG: @@ -1151,7 +1155,7 @@ build_btf_type_table(struct hashmap *tab, enum bpf_obj_type type, fd = bpf_prog_get_fd_by_id(id); break; case BPF_OBJ_MAP: - fd = bpf_map_get_fd_by_id(id); + fd = bpf_map_get_fd_by_id_opts(id, &opts_ro); break; default: err = -1; diff --git a/tools/bpf/bpftool/common.c b/tools/bpf/bpftool/common.c index ecfa790adc13..b07317d2842f 100644 --- a/tools/bpf/bpftool/common.c +++ b/tools/bpf/bpftool/common.c @@ -4,6 +4,7 @@ #ifndef _GNU_SOURCE #define _GNU_SOURCE #endif +#include <assert.h> #include <ctype.h> #include <errno.h> #include <fcntl.h> @@ -193,7 +194,8 @@ int mount_tracefs(const char *target) return err; }

-int open_obj_pinned(const char *path, bool quiet) +int open_obj_pinned(const char *path, bool quiet, + const struct bpf_obj_get_opts *opts) { char *pname; int fd = -1; @@ -205,7 +207,7 @@ int open_obj_pinned(const char *path, bool quiet) goto out_ret; }

- fd = bpf_obj_get(pname); + fd = bpf_obj_get_opts(pname, opts); if (fd < 0) { if (!quiet) p_err("bpf obj get (%s): %s", pname, @@ -221,12 +223,13 @@ int open_obj_pinned(const char *path, bool quiet) return fd; }

-int open_obj_pinned_any(const char *path, enum bpf_obj_type exp_type) +int open_obj_pinned_any(const char *path, enum bpf_obj_type exp_type, + const struct bpf_obj_get_opts *opts) { enum bpf_obj_type type; int fd;

- fd = open_obj_pinned(path, false); + fd = open_obj_pinned(path, false, opts); if (fd < 0) return -1;

@@ -555,7 +558,7 @@ static int do_build_table_cb(const char *fpath, const struct stat *sb, if (typeflag != FTW_F) goto out_ret;

- fd = open_obj_pinned(fpath, true); + fd = open_obj_pinned(fpath, true, NULL); if (fd < 0) goto out_ret;

@@ -928,7 +931,7 @@ int prog_parse_fds(int *argc, char ***argv, int **fds) path = **argv; NEXT_ARGP();

- (*fds)[0] = open_obj_pinned_any(path, BPF_OBJ_PROG); + (*fds)[0] = open_obj_pinned_any(path, BPF_OBJ_PROG, NULL); if ((*fds)[0] < 0) return -1; return 1; @@ -965,7 +968,8 @@ int prog_parse_fd(int *argc, char ***argv) return fd; }

-static int map_fd_by_name(char *name, int **fds) +static int map_fd_by_name(char *name, int **fds, + const struct bpf_get_fd_by_id_opts *opts) { unsigned int id = 0; int fd, nb_fds = 0; @@ -973,6 +977,7 @@ static int map_fd_by_name(char *name, int **fds) int err;

while (true) { + LIBBPF_OPTS(bpf_get_fd_by_id_opts, opts_ro); struct bpf_map_info info = {}; __u32 len = sizeof(info);

@@ -985,7 +990,9 @@ static int map_fd_by_name(char *name, int **fds) return nb_fds; }

- fd = bpf_map_get_fd_by_id(id); + /* Request a read-only fd to query the map info */ + opts_ro.open_flags = BPF_F_RDONLY; + fd = bpf_map_get_fd_by_id_opts(id, &opts_ro); if (fd < 0) { p_err("can't get map by id (%u): %s", id, strerror(errno)); @@ -1004,6 +1011,19 @@ static int map_fd_by_name(char *name, int **fds) continue; }

+ /* Get an fd with the requested options, if they differ + * from the read-only options used to get the fd above. + */ + if (memcmp(opts, &opts_ro, sizeof(opts_ro))) { + close(fd); + fd = bpf_map_get_fd_by_id_opts(id, opts); + if (fd < 0) { + p_err("can't get map by id (%u): %s", id, + strerror(errno)); + goto err_close_fds; + } + } + if (nb_fds > 0) { tmp = realloc(*fds, (nb_fds + 1) * sizeof(int)); if (!tmp) { @@ -1023,8 +1043,13 @@ static int map_fd_by_name(char *name, int **fds) return -1; }

-int map_parse_fds(int *argc, char ***argv, int **fds) +int map_parse_fds(int *argc, char ***argv, int **fds, __u32 open_flags) { + LIBBPF_OPTS(bpf_get_fd_by_id_opts, opts); + + assert((open_flags & ~BPF_F_RDONLY) == 0); + opts.open_flags = open_flags; + if (is_prefix(**argv, "id")) { unsigned int id; char *endptr; @@ -1038,7 +1063,7 @@ int map_parse_fds(int *argc, char ***argv, int **fds) } NEXT_ARGP();

- (*fds)[0] = bpf_map_get_fd_by_id(id); + (*fds)[0] = bpf_map_get_fd_by_id_opts(id, &opts); if ((*fds)[0] < 0) { p_err("get map by id (%u): %s", id, strerror(errno)); return -1; @@ -1056,16 +1081,18 @@ int map_parse_fds(int *argc, char ***argv, int **fds) } NEXT_ARGP();

- return map_fd_by_name(name, fds); + return map_fd_by_name(name, fds, &opts); } else if (is_prefix(**argv, "pinned")) { char *path; + LIBBPF_OPTS(bpf_obj_get_opts, get_opts); + get_opts.file_flags = open_flags;

NEXT_ARGP();

path = **argv; NEXT_ARGP();

- (*fds)[0] = open_obj_pinned_any(path, BPF_OBJ_MAP); + (*fds)[0] = open_obj_pinned_any(path, BPF_OBJ_MAP, &get_opts); if ((*fds)[0] < 0) return -1; return 1; @@ -1075,7 +1102,7 @@ int map_parse_fds(int *argc, char ***argv, int **fds) return -1; }

-int map_parse_fd(int *argc, char ***argv) +int map_parse_fd(int *argc, char ***argv, __u32 open_flags) { int *fds = NULL; int nb_fds, fd; @@ -1085,7 +1112,7 @@ int map_parse_fd(int *argc, char ***argv) p_err("mem alloc failed"); return -1; } - nb_fds = map_parse_fds(argc, argv, &fds); + nb_fds = map_parse_fds(argc, argv, &fds, open_flags); if (nb_fds != 1) { if (nb_fds > 1) { p_err("several maps match this handle"); @@ -1103,12 +1130,12 @@ int map_parse_fd(int *argc, char ***argv) }

int map_parse_fd_and_info(int *argc, char ***argv, struct bpf_map_info *info, - __u32 *info_len) + __u32 *info_len, __u32 open_flags) { int err; int fd;

- fd = map_parse_fd(argc, argv); + fd = map_parse_fd(argc, argv, open_flags); if (fd < 0) return -1;

diff --git a/tools/bpf/bpftool/iter.c b/tools/bpf/bpftool/iter.c index 5c39c2ed36a2..df5f0d1e07e8 100644 --- a/tools/bpf/bpftool/iter.c +++ b/tools/bpf/bpftool/iter.c @@ -37,7 +37,7 @@ static int do_pin(int argc, char **argv) return -1; }

- map_fd = map_parse_fd(&argc, &argv); + map_fd = map_parse_fd(&argc, &argv, BPF_F_RDONLY); if (map_fd < 0) return -1;

diff --git a/tools/bpf/bpftool/link.c b/tools/bpf/bpftool/link.c index 03513ffffb79..a773e05d5ade 100644 --- a/tools/bpf/bpftool/link.c +++ b/tools/bpf/bpftool/link.c @@ -117,7 +117,7 @@ static int link_parse_fd(int *argc, char ***argv) path = **argv; NEXT_ARGP();

- return open_obj_pinned_any(path, BPF_OBJ_LINK); + return open_obj_pinned_any(path, BPF_OBJ_LINK, NULL); }

p_err("expected 'id' or 'pinned', got: '%s'?", **argv); diff --git a/tools/bpf/bpftool/main.h b/tools/bpf/bpftool/main.h index 9eb764fe4cc8..6db704fda5c0 100644 --- a/tools/bpf/bpftool/main.h +++ b/tools/bpf/bpftool/main.h @@ -15,6 +15,7 @@

#include <bpf/hashmap.h> #include <bpf/libbpf.h> +#include <bpf/bpf.h>

#include "json_writer.h"

@@ -140,8 +141,10 @@ void get_prog_full_name(const struct bpf_prog_info *prog_info, int prog_fd, int get_fd_type(int fd); const char *get_fd_type_name(enum bpf_obj_type type); char *get_fdinfo(int fd, const char *key); -int open_obj_pinned(const char *path, bool quiet); -int open_obj_pinned_any(const char *path, enum bpf_obj_type exp_type); +int open_obj_pinned(const char *path, bool quiet, + const struct bpf_obj_get_opts *opts); +int open_obj_pinned_any(const char *path, enum bpf_obj_type exp_type, + const struct bpf_obj_get_opts *opts); int mount_bpffs_for_file(const char *file_name); int create_and_mount_bpffs_dir(const char *dir_name); int do_pin_any(int argc, char **argv, int (*get_fd_by_id)(int *, char ***)); @@ -167,10 +170,10 @@ int do_iter(int argc, char **argv) __weak; int parse_u32_arg(int *argc, char ***argv, __u32 *val, const char *what); int prog_parse_fd(int *argc, char ***argv); int prog_parse_fds(int *argc, char ***argv, int **fds); -int map_parse_fd(int *argc, char ***argv); -int map_parse_fds(int *argc, char ***argv, int **fds); +int map_parse_fd(int *argc, char ***argv, __u32 open_flags); +int map_parse_fds(int *argc, char ***argv, int **fds, __u32 open_flags); int map_parse_fd_and_info(int *argc, char ***argv, struct bpf_map_info *info, - __u32 *info_len); + __u32 *info_len, __u32 open_flags);

struct bpf_prog_linfo; #if defined(HAVE_LLVM_SUPPORT) || defined(HAVE_LIBBFD_SUPPORT) diff --git a/tools/bpf/bpftool/map.c b/tools/bpf/bpftool/map.c index 81cc668b4b05..c9de44a45778 100644 --- a/tools/bpf/bpftool/map.c +++ b/tools/bpf/bpftool/map.c @@ -337,9 +337,9 @@ static void fill_per_cpu_value(struct bpf_map_info *info, void *value) memcpy(value + i * step, value, info->value_size); }

-static int parse_elem(char **argv, struct bpf_map_info *info, - void *key, void *value, __u32 key_size, __u32 value_size, - __u32 *flags, __u32 **value_fd) +static int parse_elem(char **argv, struct bpf_map_info *info, void *key, + void *value, __u32 key_size, __u32 value_size, + __u32 *flags, __u32 **value_fd, __u32 open_flags) { if (!*argv) { if (!key && !value) @@ -362,7 +362,7 @@ static int parse_elem(char **argv, struct bpf_map_info *info, return -1;

return parse_elem(argv, info, NULL, value, key_size, value_size, - flags, value_fd); + flags, value_fd, open_flags); } else if (is_prefix(*argv, "value")) { int fd;

@@ -388,7 +388,7 @@ static int parse_elem(char **argv, struct bpf_map_info *info, return -1; }

- fd = map_parse_fd(&argc, &argv); + fd = map_parse_fd(&argc, &argv, open_flags); if (fd < 0) return -1;

@@ -424,7 +424,7 @@ static int parse_elem(char **argv, struct bpf_map_info *info, }

return parse_elem(argv, info, key, NULL, key_size, value_size, - flags, NULL); + flags, NULL, open_flags); } else if (is_prefix(*argv, "any") || is_prefix(*argv, "noexist") || is_prefix(*argv, "exist")) { if (!flags) { @@ -440,7 +440,7 @@ static int parse_elem(char **argv, struct bpf_map_info *info, *flags = BPF_EXIST;

return parse_elem(argv + 1, info, key, value, key_size, - value_size, NULL, value_fd); + value_size, NULL, value_fd, open_flags); }

p_err("expected key or value, got: %s", *argv); @@ -639,7 +639,7 @@ static int do_show_subset(int argc, char **argv) p_err("mem alloc failed"); return -1; } - nb_fds = map_parse_fds(&argc, &argv, &fds); + nb_fds = map_parse_fds(&argc, &argv, &fds, BPF_F_RDONLY); if (nb_fds < 1) goto exit_free;

@@ -672,12 +672,15 @@ static int do_show_subset(int argc, char **argv)

static int do_show(int argc, char **argv) { + LIBBPF_OPTS(bpf_get_fd_by_id_opts, opts); struct bpf_map_info info = {}; __u32 len = sizeof(info); __u32 id = 0; int err; int fd;

+ opts.open_flags = BPF_F_RDONLY; + if (show_pinned) { map_table = hashmap__new(hash_fn_for_key_as_id, equal_fn_for_key_as_id, NULL); @@ -707,7 +710,7 @@ static int do_show(int argc, char **argv) break; }

- fd = bpf_map_get_fd_by_id(id); + fd = bpf_map_get_fd_by_id_opts(id, &opts); if (fd < 0) { if (errno == ENOENT) continue; @@ -909,7 +912,7 @@ static int do_dump(int argc, char **argv) p_err("mem alloc failed"); return -1; } - nb_fds = map_parse_fds(&argc, &argv, &fds); + nb_fds = map_parse_fds(&argc, &argv, &fds, BPF_F_RDONLY); if (nb_fds < 1) goto exit_free;

@@ -997,7 +1000,7 @@ static int do_update(int argc, char **argv) if (argc < 2) usage();

- fd = map_parse_fd_and_info(&argc, &argv, &info, &len); + fd = map_parse_fd_and_info(&argc, &argv, &info, &len, 0); if (fd < 0) return -1;

@@ -1006,7 +1009,7 @@ static int do_update(int argc, char **argv) goto exit_free;

err = parse_elem(argv, &info, key, value, info.key_size, - info.value_size, &flags, &value_fd); + info.value_size, &flags, &value_fd, 0); if (err) goto exit_free;

@@ -1076,7 +1079,7 @@ static int do_lookup(int argc, char **argv) if (argc < 2) usage();

- fd = map_parse_fd_and_info(&argc, &argv, &info, &len); + fd = map_parse_fd_and_info(&argc, &argv, &info, &len, BPF_F_RDONLY); if (fd < 0) return -1;

@@ -1084,7 +1087,8 @@ static int do_lookup(int argc, char **argv) if (err) goto exit_free;

- err = parse_elem(argv, &info, key, NULL, info.key_size, 0, NULL, NULL); + err = parse_elem(argv, &info, key, NULL, info.key_size, 0, NULL, NULL, + BPF_F_RDONLY); if (err) goto exit_free;

@@ -1127,7 +1131,7 @@ static int do_getnext(int argc, char **argv) if (argc < 2) usage();

- fd = map_parse_fd_and_info(&argc, &argv, &info, &len); + fd = map_parse_fd_and_info(&argc, &argv, &info, &len, BPF_F_RDONLY); if (fd < 0) return -1;

@@ -1140,8 +1144,8 @@ static int do_getnext(int argc, char **argv) }

if (argc) { - err = parse_elem(argv, &info, key, NULL, info.key_size, 0, - NULL, NULL); + err = parse_elem(argv, &info, key, NULL, info.key_size, 0, NULL, + NULL, BPF_F_RDONLY); if (err) goto exit_free; } else { @@ -1198,7 +1202,7 @@ static int do_delete(int argc, char **argv) if (argc < 2) usage();

- fd = map_parse_fd_and_info(&argc, &argv, &info, &len); + fd = map_parse_fd_and_info(&argc, &argv, &info, &len, 0); if (fd < 0) return -1;

@@ -1209,7 +1213,8 @@ static int do_delete(int argc, char **argv) goto exit_free; }

- err = parse_elem(argv, &info, key, NULL, info.key_size, 0, NULL, NULL); + err = parse_elem(argv, &info, key, NULL, info.key_size, 0, NULL, NULL, + 0); if (err) goto exit_free;

@@ -1226,11 +1231,16 @@ static int do_delete(int argc, char **argv) return err; }

+static int map_parse_read_only_fd(int *argc, char ***argv) +{ + return map_parse_fd(argc, argv, BPF_F_RDONLY); +} + static int do_pin(int argc, char **argv) { int err;

- err = do_pin_any(argc, argv, map_parse_fd); + err = do_pin_any(argc, argv, map_parse_read_only_fd); if (!err && json_output) jsonw_null(json_wtr); return err; @@ -1319,7 +1329,7 @@ static int do_create(int argc, char **argv) if (!REQ_ARGS(2)) usage(); inner_map_fd = map_parse_fd_and_info(&argc, &argv, - &info, &len); + &info, &len, BPF_F_RDONLY); if (inner_map_fd < 0) return -1; attr.inner_map_fd = inner_map_fd; @@ -1368,7 +1378,7 @@ static int do_pop_dequeue(int argc, char **argv) if (argc < 2) usage();

- fd = map_parse_fd_and_info(&argc, &argv, &info, &len); + fd = map_parse_fd_and_info(&argc, &argv, &info, &len, 0); if (fd < 0) return -1;

@@ -1407,7 +1417,7 @@ static int do_freeze(int argc, char **argv) if (!REQ_ARGS(2)) return -1;

- fd = map_parse_fd(&argc, &argv); + fd = map_parse_fd(&argc, &argv, 0); if (fd < 0) return -1;

diff --git a/tools/bpf/bpftool/map_perf_ring.c b/tools/bpf/bpftool/map_perf_ring.c index 552b4ca40c27..bcb767e2d673 100644 --- a/tools/bpf/bpftool/map_perf_ring.c +++ b/tools/bpf/bpftool/map_perf_ring.c @@ -128,7 +128,8 @@ int do_event_pipe(int argc, char **argv) int err, map_fd;

map_info_len = sizeof(map_info); - map_fd = map_parse_fd_and_info(&argc, &argv, &map_info, &map_info_len); + map_fd = map_parse_fd_and_info(&argc, &argv, &map_info, &map_info_len, + 0); if (map_fd < 0) return -1;

diff --git a/tools/bpf/bpftool/prog.c b/tools/bpf/bpftool/prog.c index 96eea8a67225..deeaa5c1ed7d 100644 --- a/tools/bpf/bpftool/prog.c +++ b/tools/bpf/bpftool/prog.c @@ -1062,7 +1062,7 @@ static int parse_attach_detach_args(int argc, char **argv, int *progfd, if (!REQ_ARGS(2)) return -EINVAL;

- *mapfd = map_parse_fd(&argc, &argv); + *mapfd = map_parse_fd(&argc, &argv, 0); if (*mapfd < 0) return *mapfd;

@@ -1608,7 +1608,7 @@ static int load_with_options(int argc, char **argv, bool first_prog_only) } NEXT_ARG();

- fd = map_parse_fd(&argc, &argv); + fd = map_parse_fd(&argc, &argv, 0); if (fd < 0) goto err_free_reuse_maps;