diff mbox series

[bpf-next,5/8] bpf: Refactor NULL-ness check in check_reg_type().

Message ID 20230404045029.82870-6-alexei.starovoitov@gmail.com (mailing list archive)
State Accepted
Commit add68b843f33d4e5dcbdc7ba6dffe7750a964159
Delegated to: BPF
Headers show
Series bpf: Follow up to RCU enforcement in the verifier. | expand

Checks

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bpf/vmtest-bpf-next-VM_Test-15 success Logs for test_progs on s390x with gcc
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netdev/series_format success Posting correctly formatted
netdev/tree_selection success Clearly marked for bpf-next, async
netdev/fixes_present success Fixes tag not required for -next series
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 28 this patch: 28
netdev/cc_maintainers warning 8 maintainers not CCed: song@kernel.org sdf@google.com haoluo@google.com yhs@fb.com john.fastabend@gmail.com kpsingh@kernel.org jolsa@kernel.org martin.lau@linux.dev
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netdev/checkpatch warning WARNING: line length of 85 exceeds 80 columns WARNING: line length of 94 exceeds 80 columns
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bpf/vmtest-bpf-next-VM_Test-21 success Logs for test_progs_no_alu32 on x86_64 with gcc
bpf/vmtest-bpf-next-VM_Test-22 success Logs for test_progs_no_alu32 on x86_64 with llvm-16
bpf/vmtest-bpf-next-VM_Test-23 success Logs for test_progs_no_alu32_parallel on aarch64 with gcc
bpf/vmtest-bpf-next-VM_Test-24 success Logs for test_progs_no_alu32_parallel on aarch64 with llvm-16
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Commit Message

Alexei Starovoitov April 4, 2023, 4:50 a.m. UTC 
From: Alexei Starovoitov <ast@kernel.org>

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>
---
 kernel/bpf/verifier.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)
diff mbox series

Patch

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 @@  static int check_reg_type(struct bpf_verifier_env *env, u32 regno,
 	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 @@  static int check_reg_type(struct bpf_verifier_env *env, u32 regno,
 		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 @@  static int check_reg_type(struct bpf_verifier_env *env, u32 regno,
 		}
 		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) {