[PATCH iproute2 -net-next] bpf: check for owner_prog_type and notify users when differ

[Daniel Borkmann]

Kernel commit 21116b7068b9 ("bpf: add owner_prog_type and accounted mem
to array map's fdinfo") added support for telling the owner prog type in
case of prog arrays. Give a notification to the user when they differ,
and the program eventually fails to load.

Signed-off-by: Daniel Borkmann <dan...@iogearbox.net>
Acked-by: Alexei Starovoitov <a...@kernel.org>
---
 lib/bpf.c | 18 ++++++++++++++----
 1 file changed, 14 insertions(+), 4 deletions(-)

diff --git a/lib/bpf.c b/lib/bpf.c
index 8a5b84b..f714993 100644
--- a/lib/bpf.c
+++ b/lib/bpf.c
@@ -273,11 +273,11 @@ static void bpf_map_pin_report(const struct bpf_elf_map 
*pin,
 }
 
 static int bpf_map_selfcheck_pinned(int fd, const struct bpf_elf_map *map,
-                                   int length)
+                                   int length, enum bpf_prog_type type)
 {
        char file[PATH_MAX], buff[4096];
        struct bpf_elf_map tmp = {}, zero = {};
-       unsigned int val;
+       unsigned int val, owner_type = 0;
        FILE *fp;
 
        snprintf(file, sizeof(file), "/proc/%d/fdinfo/%d", getpid(), fd);
@@ -299,10 +299,19 @@ static int bpf_map_selfcheck_pinned(int fd, const struct 
bpf_elf_map *map,
                        tmp.max_elem = val;
                else if (sscanf(buff, "map_flags:\t%i", &val) == 1)
                        tmp.flags = val;
+               else if (sscanf(buff, "owner_prog_type:\t%i", &val) == 1)
+                       owner_type = val;
        }
 
        fclose(fp);
 
+       /* The decision to reject this is on kernel side eventually, but
+        * at least give the user a chance to know what's wrong.
+        */
+       if (owner_type && owner_type != type)
+               fprintf(stderr, "Program array map owner types differ: %u (obj) 
!= %u (pin)\n",
+                       type, owner_type);
+
        if (!memcmp(&tmp, map, length)) {
                return 0;
        } else {
@@ -818,7 +827,8 @@ int bpf_graft_map(const char *map_path, uint32_t *key, int 
argc, char **argv)
        }
 
        ret = bpf_map_selfcheck_pinned(map_fd, &test,
-                                      offsetof(struct bpf_elf_map, max_elem));
+                                      offsetof(struct bpf_elf_map, max_elem),
+                                      type);
        if (ret < 0) {
                fprintf(stderr, "Map \'%s\' self-check failed!\n", map_path);
                goto out_map;
@@ -1300,7 +1310,7 @@ static int bpf_map_attach(const char *name, const struct 
bpf_elf_map *map,
        if (fd > 0) {
                ret = bpf_map_selfcheck_pinned(fd, map,
                                               offsetof(struct bpf_elf_map,
-                                                       id));
+                                                       id), ctx->type);
                if (ret < 0) {
                        close(fd);
                        fprintf(stderr, "Map \'%s\' self-check failed!\n",
-- 
1.9.3