libbpf: Sanitise internal map names so they are not rejected by the kernel

The kernel only accepts map names with alphanumeric characters, underscores
and periods in their name. However, the auto-generated internal map names
used by libbpf takes their prefix from the user-supplied BPF object name,
which has no such restriction. This can lead to "Invalid argument" errors
when trying to load a BPF program using global variables.

Fix this by sanitising the map names, replacing any non-allowed characters
with underscores.

Fixes: d859900c4c56 ("bpf, libbpf: support global data/bss/rodata sections")
Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20200217171701.215215-1-toke@redhat.com

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 514b1a524abbc0ff49bfe25fa2244eb50b860e1c..7469c7dcc15e71fb82e0c8d0a1426cce7b7e2127 100644 (file)
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -24,6 +24,7 @@
 #include <endian.h>
 #include <fcntl.h>
 #include <errno.h>
+#include <ctype.h>
 #include <asm/unistd.h>
 #include <linux/err.h>
 #include <linux/kernel.h>
@@ -1283,7 +1284,7 @@ static size_t bpf_map_mmap_sz(const struct bpf_map *map)
 static char *internal_map_name(struct bpf_object *obj,
                               enum libbpf_map_type type)
 {
-       char map_name[BPF_OBJ_NAME_LEN];
+       char map_name[BPF_OBJ_NAME_LEN], *p;
        const char *sfx = libbpf_type_to_btf_name[type];
        int sfx_len = max((size_t)7, strlen(sfx));
        int pfx_len = min((size_t)BPF_OBJ_NAME_LEN - sfx_len - 1,
@@ -1292,6 +1293,11 @@ static char *internal_map_name(struct bpf_object *obj,
        snprintf(map_name, sizeof(map_name), "%.*s%.*s", pfx_len, obj->name,
                 sfx_len, libbpf_type_to_btf_name[type]);
 
+       /* sanitise map name to characters allowed by kernel */
+       for (p = map_name; *p && p < map_name + sizeof(map_name); p++)
+               if (!isalnum(*p) && *p != '_' && *p != '.')
+                       *p = '_';
+
        return strdup(map_name);
 }