2025-02-11 16:45 UTC+0800 ~ Rong Tao <rtoax@xxxxxxxxxxx>
> 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 error is
> reported. This submission checks the length of the map name.
>
> Signed-off-by: Rong Tao <rongtao@xxxxxxxx>
> ---
> tools/bpf/bpftool/map.c | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> diff --git a/tools/bpf/bpftool/map.c b/tools/bpf/bpftool/map.c
> index ed4a9bd82931..fa00f7865065 100644
> --- a/tools/bpf/bpftool/map.c
> +++ b/tools/bpf/bpftool/map.c
> @@ -1330,6 +1330,12 @@ static int do_create(int argc, char **argv)
> goto exit;
> }
>
> + if (strlen(map_name) > BPF_OBJ_NAME_LEN - 1) {
> + p_err("The map name is too long, should be less than %d\n",
Nit: I'd drop "The" (and the capital letter) for consistency with other
messages in bpftool; and I'd replace "less than ..." with "no longer
than %d characters\n" to make it explicit and avoid confusion between
"strictly less" and "less or equal".
> + BPF_OBJ_NAME_LEN - 1);
> + goto exit;
> + }
> +
> set_max_rlimit();
>
> fd = bpf_map_create(map_type, map_name, key_size, value_size, max_entries, &attr);
There's no need to defer the check until after we've parsed all
arguments. Can you move it to the location where we retrieve the name,
please?:
[...]
} else if (is_prefix(*argv, "name")) {
NEXT_ARG();
map_name = GET_ARG();
} else ...
pw-bot: cr
Apart from these, it's a good idea to fix it, thank you!
Quentin
