From: Kumar Kartikeya Dwivedi memxor@gmail.com
[ Upstream commit 45ce4b4f9009102cd9f581196d480a59208690c1 ]
When commit e6ac2450d6de ("bpf: Support bpf program calling kernel function") added kfunc support, it defined reg2btf_ids as a cheap way to translate the verifier reg type to the appropriate btf_vmlinux BTF ID, however commit c25b2ae13603 ("bpf: Replace PTR_TO_XXX_OR_NULL with PTR_TO_XXX | PTR_MAYBE_NULL") moved the __BPF_REG_TYPE_MAX from the last member of bpf_reg_type enum to after the base register types, and defined other variants using type flag composition. However, now, the direct usage of reg->type to index into reg2btf_ids may no longer fall into __BPF_REG_TYPE_MAX range, and hence lead to out of bounds access and kernel crash on dereference of bad pointer.
Fixes: c25b2ae13603 ("bpf: Replace PTR_TO_XXX_OR_NULL with PTR_TO_XXX | PTR_MAYBE_NULL") Signed-off-by: Kumar Kartikeya Dwivedi memxor@gmail.com Signed-off-by: Alexei Starovoitov ast@kernel.org Link: https://lore.kernel.org/bpf/20220216201943.624869-1-memxor@gmail.com Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/bpf/btf.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c index 1621f9d45fbda..c9da250fee38c 100644 --- a/kernel/bpf/btf.c +++ b/kernel/bpf/btf.c @@ -5676,7 +5676,8 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env, } if (check_ctx_reg(env, reg, regno)) return -EINVAL; - } else if (is_kfunc && (reg->type == PTR_TO_BTF_ID || reg2btf_ids[reg->type])) { + } else if (is_kfunc && (reg->type == PTR_TO_BTF_ID || + (reg2btf_ids[base_type(reg->type)] && !type_flag(reg->type)))) { const struct btf_type *reg_ref_t; const struct btf *reg_btf; const char *reg_ref_tname; @@ -5694,7 +5695,7 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env, reg_ref_id = reg->btf_id; } else { reg_btf = btf_vmlinux; - reg_ref_id = *reg2btf_ids[reg->type]; + reg_ref_id = *reg2btf_ids[base_type(reg->type)]; }
reg_ref_t = btf_type_skip_modifiers(reg_btf, reg_ref_id,