bpf: mark a NULL kfunc argument precisegrafted

check_kfunc_arg() allows bpf_register_is_null() for nullable arguments
w/o marking the underlying scalar register precise. Hence a checkpoint
created on such a path would prune against arbitrary scalar value.

Fixes: 3bda08b63670 ("bpf: Allow NULL buffers in bpf_dynptr_slice(_rw)")
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20260904-register-is-null-precise-fixes-v1-5-0f5a360ff15d@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 61 insertions, 0 deletions

diff --git a/security/apparmor/crypto.c b/security/apparmor/crypto.c
new file mode 100644
index 000000000..d8a7bde94
--- /dev/null
+++ b/security/apparmor/crypto.c
@@ -0,0 +1,61 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * AppArmor security module
+ *
+ * This file contains AppArmor policy loading interface function definitions.
+ *
+ * Copyright 2013 Canonical Ltd.
+ *
+ * Fns to provide a checksum of policy that has been loaded this can be
+ * compared to userspace policy compiles to check loaded policy is what
+ * it should be.
+ */
+
+#include <crypto/sha2.h>
+
+#include "include/apparmor.h"
+#include "include/crypto.h"
+
+unsigned int aa_hash_size(void)
+{
+	return SHA256_DIGEST_SIZE;
+}
+
+char *aa_calc_hash(void *data, size_t len)
+{
+	char *hash;
+
+	hash = kzalloc(SHA256_DIGEST_SIZE, GFP_KERNEL);
+	if (!hash)
+		return ERR_PTR(-ENOMEM);
+
+	sha256(data, len, hash);
+	return hash;
+}
+
+int aa_calc_profile_hash(struct aa_profile *profile, u32 version, void *start,
+			 size_t len)
+{
+	struct sha256_ctx sctx;
+	__le32 le32_version = cpu_to_le32(version);
+
+	if (!aa_g_hash_policy)
+		return 0;
+
+	profile->hash = kzalloc(SHA256_DIGEST_SIZE, GFP_KERNEL);
+	if (!profile->hash)
+		return -ENOMEM;
+
+	sha256_init(&sctx);
+	sha256_update(&sctx, (u8 *)&le32_version, 4);
+	sha256_update(&sctx, (u8 *)start, len);
+	sha256_final(&sctx, profile->hash);
+	return 0;
+}
+
+int __init init_profile_hash(void)
+{
+	if (apparmor_initialized)
+		aa_info_message("AppArmor sha256 policy hashing enabled");
+	return 0;
+}