On Fri, Jul 14, 2023 at 10:56:00AM -0700, Alexei Starovoitov wrote:
On Fri, Jul 14, 2023 at 7:20 AM Anton Protopopov aspsk@isovalent.com wrote:
Patch verifier to regard values of type CONST_PTR_TO_MAP as trusted pointers to struct bpf_map. This allows kfuncs to work with `struct bpf_map *` arguments.
Save some bytes by defining btf_bpf_map_id as BTF_ID_LIST_GLOBAL_SINGLE (which is u32[1]), not as BTF_ID_LIST (which is u32[64]).
Signed-off-by: Anton Protopopov aspsk@isovalent.com
include/linux/btf_ids.h | 1 + kernel/bpf/map_iter.c | 3 +-- kernel/bpf/verifier.c | 5 ++++- 3 files changed, 6 insertions(+), 3 deletions(-)
diff --git a/include/linux/btf_ids.h b/include/linux/btf_ids.h index 00950cc03bff..a3462a9b8e18 100644 --- a/include/linux/btf_ids.h +++ b/include/linux/btf_ids.h @@ -267,5 +267,6 @@ MAX_BTF_TRACING_TYPE, extern u32 btf_tracing_ids[]; extern u32 bpf_cgroup_btf_id[]; extern u32 bpf_local_storage_map_btf_id[]; +extern u32 btf_bpf_map_id[];
#endif diff --git a/kernel/bpf/map_iter.c b/kernel/bpf/map_iter.c index d06d3b7150e5..b67996147895 100644 --- a/kernel/bpf/map_iter.c +++ b/kernel/bpf/map_iter.c @@ -78,8 +78,7 @@ static const struct seq_operations bpf_map_seq_ops = { .show = bpf_map_seq_show, };
-BTF_ID_LIST(btf_bpf_map_id) -BTF_ID(struct, bpf_map) +BTF_ID_LIST_GLOBAL_SINGLE(btf_bpf_map_id, struct, bpf_map)
static const struct bpf_iter_seq_info bpf_map_seq_info = { .seq_ops = &bpf_map_seq_ops, diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 0b9da95331d7..5663f97ef292 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -5419,6 +5419,9 @@ static bool is_trusted_reg(const struct bpf_reg_state *reg) if (reg->ref_obj_id) return true;
if (reg->type == CONST_PTR_TO_MAP)return true;Overall it looks great. Instead of above, how about the following instead:
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 0b9da95331d7..cd08167dc347 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -10775,7 +10775,7 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_ if (!is_kfunc_trusted_args(meta) && !is_kfunc_rcu(meta)) break;
if (!is_trusted_reg(reg)) {
if (!is_trusted_reg(reg) &&!reg2btf_ids[base_type(reg->type)]) {
This way we won't need to list every convertible type in is_trusted_reg.
I'm a bit hesitant to put reg2btf_ids[] check directly into is_trusted_reg(). Maybe it's ok, but it needs more analysis.
I am not sure I see a difference in adding a check you proposed above and adding the reg2btf_ids[] check directly into the is_trusted_reg() function. Basically, we say "if type is in reg2btf_ids[], then consider it trusted" in both cases. AFAIS, currently the reg2btf_ids[] contains only trusted types, however, could it happen that we add a non-trusted type there?
So, I would leave the patch as is (which also makes sense because the const-ptr-to-map is a special case), or add the "reg2btf_ids[] check" directly into the is_trusted_reg() function.