[PATCH bpf-next v4] bpftool: Check map name length when map create

[Rong Tao]

From: Rong Tao <rongtao@xxxxxxxx>

The size of struct bpf_map::name is BPF_OBJ_NAME_LEN (16).

bpf(2) {
  map_create() {
    bpf_obj_name_cpy(map->name, attr->map_name, sizeof(attr->map_name));
  }
}

When specifying a map name using bpftool map create name, no error is
reported if the name length is greater than 15.

    $ sudo bpftool map create /sys/fs/bpf/12345678901234567890 \
        type array key 4 value 4 entries 5 name 12345678901234567890

Users will think that 12345678901234567890 is legal, but this name cannot
be used to index a map.

    $ sudo bpftool map show name 12345678901234567890
    Error: can't parse name

    $ sudo bpftool map show
    ...
    1249: array  name 123456789012345  flags 0x0
    	key 4B  value 4B  max_entries 5  memlock 304B

    $ sudo bpftool map show name 123456789012345
    1249: array  name 123456789012345  flags 0x0
    	key 4B  value 4B  max_entries 5  memlock 304B

The map name provided in the command line is truncated, but no warning is
reported. This submission checks the length of the map name.

Reviewed-by: Quentin Monnet <qmo@xxxxxxxxxx>
Signed-off-by: Rong Tao <rongtao@xxxxxxxx>
---
v3: https://lore.kernel.org/lkml/tencent_AF066A426F591F977D2A73AF00A34A883808@xxxxxx/
v2: https://lore.kernel.org/lkml/tencent_26592A2BAF08A3A688A50600421559929708@xxxxxx/
v1: https://lore.kernel.org/lkml/tencent_1C4444032C2188ACD04B4995B0D78F510607@xxxxxx/
---
 tools/bpf/bpftool/map.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/tools/bpf/bpftool/map.c b/tools/bpf/bpftool/map.c
index ed4a9bd82931..81cc668b4b05 100644
--- a/tools/bpf/bpftool/map.c
+++ b/tools/bpf/bpftool/map.c
@@ -1270,6 +1270,10 @@ static int do_create(int argc, char **argv)
 		} else if (is_prefix(*argv, "name")) {
 			NEXT_ARG();
 			map_name = GET_ARG();
+			if (strlen(map_name) > BPF_OBJ_NAME_LEN - 1) {
+				p_info("Warning: map name is longer than %u characters, it will be truncated.",
+				      BPF_OBJ_NAME_LEN - 1);
+			}
 		} else if (is_prefix(*argv, "key")) {
 			if (parse_u32_arg(&argc, &argv, &key_size,
 					  "key size"))
-- 
2.48.1