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authorKumar Kartikeya Dwivedi <memxor@gmail.com>2022-02-17 01:49:43 +0530
committerAlexei Starovoitov <ast@kernel.org>2022-02-16 12:46:51 -0800
commit45ce4b4f9009102cd9f581196d480a59208690c1 (patch)
tree806a5cc566416b243fb0fabc7a7adbf7ab97efea /kernel
parent61d06f01f9710b327a53492e5add9f972eb909b3 (diff)
bpf: Fix crash due to out of bounds access into reg2btf_ids.
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
Diffstat (limited to 'kernel')
-rw-r--r--kernel/bpf/btf.c5
1 files 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,