On 2/12/25 05:07, Andrii Nakryiko wrote:
On Tue, Feb 11, 2025 at 2:48 AM Quentin Monnet <qmo@xxxxxxxxxx> wrote:
2025-02-11 18:38 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>
Reviewed-by: Quentin Monnet <qmo@xxxxxxxxxx>
Would it make sense to just warn but proceed with a truncated name?
libbpf truncates the name when creating a map, but preserves the
original name in BTF (and in memory, fetchable through
bpf_map__name()). So from the user's perspective that map is still
named "blah-blah-something-long", even if the kernel records just a
prefix of that.
Basically, instead of forcing users to count the first 15 characters,
warn, but do the right thing anyways?
Yes, you're right, i'll submit v3.
Rong Tao
Thank you!
