bpf: Don't echo user-supplied map info fields back to userspace

Commit ea2e6467ac36 ("bpf: Return hashes of maps in BPF_OBJ_GET_INFO_BY_FD")
started copying struct bpf_map_info in from userspace in order to read
the new hash and hash_size input fields. Before that, the kernel ignored
the contents of the user buffer and returned a zeroed structure with only
the output fields filled in.

Some output fields are only set for certain maps: btf_id, btf_key_type_id
and btf_value_type_id when the map has BTF (and btf_vmlinux_id for
struct_ops maps, ifindex, netns_dev and netns_ino when the map is
offloaded). For all other maps, these fields now return whatever
userspace passed in before.

This breaks userspace which reuses one bpf_map_info for several queries.
Restore the original behavior by zeroing the structure and copying in
only hash and hash_size from userspace before the output fields are
filled in.

Fixes: ea2e6467ac36 ("bpf: Return hashes of maps in BPF_OBJ_GET_INFO_BY_FD")
Reported-by: Quentin Monnet <qmo@kernel.org>
Reported-by: Tianyi Chen <hi@tychen.cc>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://patch.msgid.link/20261016191635.662690-1-daniel@iogearbox.net

0 files changed, 0 insertions, 0 deletions