From: Andrii Nakryiko andriin@fb.com
[ Upstream commit 1acc5d5c5832da9a98b22374a8fae08ffe31b3f8 ]
BTF verifier has a size resolution bug which in some circumstances leads to invalid size resolution for, e.g., TYPEDEF modifier. This happens if we have [1] PTR -> [2] TYPEDEF -> [3] ARRAY, in which case due to being in pointer context ARRAY size won't be resolved (because for pointer it doesn't matter, so it's a sink in pointer context), but it will be permanently remembered as zero for TYPEDEF and TYPEDEF will be marked as RESOLVED. Eventually ARRAY size will be resolved correctly, but TYPEDEF resolved_size won't be updated anymore. This, subsequently, will lead to erroneous map creation failure, if that TYPEDEF is specified as either key or value, as key_size/value_size won't correspond to resolved size of TYPEDEF (kernel will believe it's zero).
Note, that if BTF was ordered as [1] ARRAY <- [2] TYPEDEF <- [3] PTR, this won't be a problem, as by the time we get to TYPEDEF, ARRAY's size is already calculated and stored.
This bug manifests itself in rejecting BTF-defined maps that use array typedef as a value type:
typedef int array_t[16];
struct { __uint(type, BPF_MAP_TYPE_ARRAY); __type(value, array_t); /* i.e., array_t *value; */ } test_map SEC(".maps");
The fix consists on not relying on modifier's resolved_size and instead using modifier's resolved_id (type ID for "concrete" type to which modifier eventually resolves) and doing size determination for that resolved type. This allow to preserve existing "early DFS termination" logic for PTR or STRUCT_OR_ARRAY contexts, but still do correct size determination for modifier types.
Fixes: eb3f595dab40 ("bpf: btf: Validate type reference") Cc: Martin KaFai Lau kafai@fb.com Signed-off-by: Andrii Nakryiko andriin@fb.com Acked-by: Martin KaFai Lau kafai@fb.com Signed-off-by: Daniel Borkmann daniel@iogearbox.net Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/bpf/btf.c | 19 ++++++++++++------- 1 file changed, 12 insertions(+), 7 deletions(-)
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c index cad09858a5f2..8614102971da 100644 --- a/kernel/bpf/btf.c +++ b/kernel/bpf/btf.c @@ -1073,11 +1073,18 @@ const struct btf_type *btf_type_id_size(const struct btf *btf, !btf_type_is_var(size_type))) return NULL;
- size = btf->resolved_sizes[size_type_id]; size_type_id = btf->resolved_ids[size_type_id]; size_type = btf_type_by_id(btf, size_type_id); if (btf_type_nosize_or_null(size_type)) return NULL; + else if (btf_type_has_size(size_type)) + size = size_type->size; + else if (btf_type_is_array(size_type)) + size = btf->resolved_sizes[size_type_id]; + else if (btf_type_is_ptr(size_type)) + size = sizeof(void *); + else + return NULL; }
*type_id = size_type_id; @@ -1602,7 +1609,6 @@ static int btf_modifier_resolve(struct btf_verifier_env *env, const struct btf_type *next_type; u32 next_type_id = t->type; struct btf *btf = env->btf; - u32 next_type_size = 0;
next_type = btf_type_by_id(btf, next_type_id); if (!next_type || btf_type_is_resolve_source_only(next_type)) { @@ -1620,7 +1626,7 @@ static int btf_modifier_resolve(struct btf_verifier_env *env, * save us a few type-following when we use it later (e.g. in * pretty print). */ - if (!btf_type_id_size(btf, &next_type_id, &next_type_size)) { + if (!btf_type_id_size(btf, &next_type_id, NULL)) { if (env_type_is_resolved(env, next_type_id)) next_type = btf_type_id_resolve(btf, &next_type_id);
@@ -1633,7 +1639,7 @@ static int btf_modifier_resolve(struct btf_verifier_env *env, } }
- env_stack_pop_resolved(env, next_type_id, next_type_size); + env_stack_pop_resolved(env, next_type_id, 0);
return 0; } @@ -1645,7 +1651,6 @@ static int btf_var_resolve(struct btf_verifier_env *env, const struct btf_type *t = v->t; u32 next_type_id = t->type; struct btf *btf = env->btf; - u32 next_type_size;
next_type = btf_type_by_id(btf, next_type_id); if (!next_type || btf_type_is_resolve_source_only(next_type)) { @@ -1675,12 +1680,12 @@ static int btf_var_resolve(struct btf_verifier_env *env, * forward types or similar that would resolve to size of * zero is allowed. */ - if (!btf_type_id_size(btf, &next_type_id, &next_type_size)) { + if (!btf_type_id_size(btf, &next_type_id, NULL)) { btf_verifier_log_type(env, v->t, "Invalid type_id"); return -EINVAL; }
- env_stack_pop_resolved(env, next_type_id, next_type_size); + env_stack_pop_resolved(env, next_type_id, 0);
return 0; }