[PATCH bpf-next 1/3] bpf: handle trusted PTR_TO_BTF_ID_OR_NULL in argument check logic

[Andrii Nakryiko <andrii@kernel.org>]

Add PTR_TRUSTED | PTR_MAYBE_NULL modifiers for PTR_TO_BTF_ID to
check_reg_type() to support passing trusted nullable PTR_TO_BTF_ID
registers into global functions accepting `__arg_trusted __arg_nullable`
arguments. This hasn't been caught earlier because tests were either
passing known non-NULL PTR_TO_BTF_ID registers or known NULL (SCALAR)
registers.

When utilizing this functionality in complicated real-world BPF
application that passes around PTR_TO_BTF_ID_OR_NULL, it became apparent
that verifier rejects valid case because check_reg_type() doesn't handle
this case explicitly. Existing check_reg_type() logic is already
anticipating this combination, so we just need to explicitly list this
combo in the switch statement.

Fixes: e2b3c4ff5d18 ("bpf: add __arg_trusted global func arg tag")
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
---
 kernel/bpf/verifier.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index cd4d780e5400..c6f566d9dc3a 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -8234,6 +8234,7 @@ static int check_reg_type(struct bpf_verifier_env *env, u32 regno,
 	switch ((int)reg->type) {
 	case PTR_TO_BTF_ID:
 	case PTR_TO_BTF_ID | PTR_TRUSTED:
+	case PTR_TO_BTF_ID | PTR_TRUSTED | PTR_MAYBE_NULL:
 	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:
-- 
2.34.1