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.
Cc: Martin KaFai Lau <kafai@xxxxxx>
Cc: Hao Luo <haoluo@xxxxxxxxxx>
Fixes: c25b2ae13603 ("bpf: Replace PTR_TO_XXX_OR_NULL with PTR_TO_XXX | PTR_MAYBE_NULL")
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@xxxxxxxxx>
--
v1 -> v2
- Use base_type(reg->type) && !type_flag(reg->type) (Alexei)
---
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 e16dafeb2450..3e23b3fa79ff 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -5688,7 +5688,8 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env,
}
if (check_ptr_off_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;
@@ -5706,7 +5707,7 @@ 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,
--
2.35.1
