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authorAlexei Starovoitov <ast@kernel.org>2023-04-03 21:50:26 -0700
committerAndrii Nakryiko <andrii@kernel.org>2023-04-04 16:57:18 -0700
commitadd68b843f33d4e5dcbdc7ba6dffe7750a964159 (patch)
treef81ce4205a4e3ea44be76de6004b4e5d3b681170 /kernel
parent91571a515d1bcdc280bb46423bb697ea7eb42ff3 (diff)
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bpf: Refactor NULL-ness check in check_reg_type().
check_reg_type() unconditionally disallows PTR_TO_BTF_ID | PTR_MAYBE_NULL. It's problematic for helpers that allow ARG_PTR_TO_BTF_ID_OR_NULL like bpf_sk_storage_get(). Allow passing PTR_TO_BTF_ID | PTR_MAYBE_NULL into such helpers. That technically includes bpf_kptr_xchg() helper, but in practice: bpf_kptr_xchg(..., bpf_cpumask_create()); is still disallowed because bpf_cpumask_create() returns ref counted pointer with ref_obj_id > 0. Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Acked-by: David Vernet <void@manifault.com> Link: https://lore.kernel.org/bpf/20230404045029.82870-6-alexei.starovoitov@gmail.com
Diffstat (limited to 'kernel')
-rw-r--r--kernel/bpf/verifier.c12
1 files changed, 8 insertions, 4 deletions
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 2cd2e0b725cd..4e7d671497f4 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -7168,6 +7168,8 @@ found:
case PTR_TO_BTF_ID:
case PTR_TO_BTF_ID | PTR_TRUSTED:
case PTR_TO_BTF_ID | MEM_RCU:
+ case PTR_TO_BTF_ID | PTR_MAYBE_NULL:
+ case PTR_TO_BTF_ID | PTR_MAYBE_NULL | MEM_RCU:
{
/* For bpf_sk_release, it needs to match against first member
* 'struct sock_common', hence make an exception for it. This
@@ -7176,6 +7178,12 @@ found:
bool strict_type_match = arg_type_is_release(arg_type) &&
meta->func_id != BPF_FUNC_sk_release;
+ if (type_may_be_null(reg->type) &&
+ (!type_may_be_null(arg_type) || arg_type_is_release(arg_type))) {
+ verbose(env, "Possibly NULL pointer passed to helper arg%d\n", regno);
+ return -EACCES;
+ }
+
if (!arg_btf_id) {
if (!compatible->btf_id) {
verbose(env, "verifier internal error: missing arg compatible BTF ID\n");
@@ -7206,10 +7214,6 @@ found:
}
break;
}
- case PTR_TO_BTF_ID | PTR_MAYBE_NULL:
- case PTR_TO_BTF_ID | PTR_MAYBE_NULL | MEM_RCU:
- verbose(env, "Possibly NULL pointer passed to helper arg%d\n", regno);
- return -EACCES;
case PTR_TO_BTF_ID | MEM_ALLOC:
if (meta->func_id != BPF_FUNC_spin_lock && meta->func_id != BPF_FUNC_spin_unlock &&
meta->func_id != BPF_FUNC_kptr_xchg) {