[PATCH 6/8] pseries/plpks: add HCALLs for PKWM wrapping key life cycle management

[Srish Srinivasan]

The PKWM trusted source uses a single wrapping key per LPAR, created only
once during trust source initialization. All the wrap and unwrap requests
are bound to this default wrapping key.

Implement H_PKS_REVOKE_OBJECT, H_PKS_UNREVOKE_OBJECT, and
H_PKS_GET_OBJECTLABELS HCALLs to enable support for revoking and unrevoking
PKWM wrapping keys, and for retrieving wrapping key labels. The label
retrieval operation (H_PKS_GET_OBJECTLABELS) applies to all wrapping keys
including the default one, while the life cycle operations
(H_PKS_REVOKE_OBJECT/H_PKS_UNREVOKE_OBJECT) apply only to user-created
wrapping keys.

Signed-off-by: Srish Srinivasan <ssrish@xxxxxxxxxxxxx>
---
 Documentation/arch/powerpc/papr_hcalls.rst |  33 ++
 arch/powerpc/include/asm/hvcall.h          |   5 +-
 arch/powerpc/include/asm/plpks.h           |  15 +
 arch/powerpc/platforms/pseries/plpks.c     | 475 ++++++++++++++++++++-
 4 files changed, 524 insertions(+), 4 deletions(-)

diff --git a/Documentation/arch/powerpc/papr_hcalls.rst b/Documentation/arch/powerpc/papr_hcalls.rst
index 44c9c8b32ae3..3455b403a048 100644
--- a/Documentation/arch/powerpc/papr_hcalls.rst
+++ b/Documentation/arch/powerpc/papr_hcalls.rst
@@ -343,6 +343,39 @@ is returned to the caller.
 H_PKS_UNWRAP_OBJECT is used to unwrap an object that was previously wrapped with
 H_PKS_WRAP_OBJECT.
 
+**H_PKS_REVOKE_OBJECT**
+
+| Input: authorization, objectlabel, objectlabellen, flags
+| Out: *object policy*
+| Return Value: *H_Success, H_Function, H_State, H_Parameter, H_P2, H_P3, H_P4,
+                H_Authority, H_Not_Found, H_Busy, H_Aborted*
+
+H_PKS_REVOKE_OBJECT is used to revoke an object in Platform Keystore.
+
+
+**H_PKS_UNREVOKE_OBJECT**
+
+| Input: authorization, objectlabel, objectlabellen, flags
+| Out: *object policy*
+| Return Value: *H_Success, H_Function, H_State, H_Parameter, H_P2, H_P3, H_P4,
+                H_Authority, H_Not_Found, H_Busy, H_Aborted*
+
+H_PKS_UNREVOKE_OBJECT is used to unrevoke an object that was previously revoked
+with H_PKS_REVOKE_OBJECT in Platform Keystore.
+
+
+**H_PKS_GET_OBJECTLABELS**
+
+| Input: authorization, continueToken, out, outlen
+| Out: *continue-token, number of object labels in the returned list, object
+        label list*
+| Return Value: *H_Success, H_Function, H_State, H_Parameter, H_P2, H_P3, H_P4,
+                H_Authority, H_Busy, H_Aborted, H_Continue*
+
+H_PKS_GET_OBJECTLABELS is used to retrieve a list of object labels owned by the
+specified consumer.
+
+
 References
 ==========
 .. [1] "Power Architecture Platform Reference"
diff --git a/arch/powerpc/include/asm/hvcall.h b/arch/powerpc/include/asm/hvcall.h
index dff90a7d7f70..4d4c2ce1dd87 100644
--- a/arch/powerpc/include/asm/hvcall.h
+++ b/arch/powerpc/include/asm/hvcall.h
@@ -340,6 +340,7 @@
 #define H_PKS_GET_CONFIG	0x41C
 #define H_PKS_SET_PASSWORD	0x420
 #define H_PKS_GEN_PASSWORD	0x424
+#define H_PKS_GET_OBJECTLABELS	0x428
 #define H_PKS_WRITE_OBJECT	0x42C
 #define H_PKS_GEN_KEY		0x430
 #define H_PKS_READ_OBJECT	0x434
@@ -362,7 +363,9 @@
 #define H_GUEST_DELETE		0x488
 #define H_PKS_WRAP_OBJECT	0x490
 #define H_PKS_UNWRAP_OBJECT	0x494
-#define MAX_HCALL_OPCODE	H_PKS_UNWRAP_OBJECT
+#define H_PKS_REVOKE_OBJECT	0x4AC
+#define H_PKS_UNREVOKE_OBJECT	0x4B0
+#define MAX_HCALL_OPCODE	H_PKS_UNREVOKE_OBJECT
 
 /* Scope args for H_SCM_UNBIND_ALL */
 #define H_UNBIND_SCOPE_ALL (0x1)
diff --git a/arch/powerpc/include/asm/plpks.h b/arch/powerpc/include/asm/plpks.h
index 8b2ffb27db5a..c39d1f07017e 100644
--- a/arch/powerpc/include/asm/plpks.h
+++ b/arch/powerpc/include/asm/plpks.h
@@ -25,6 +25,7 @@
 #define PLPKS_SIGNEDUPDATE	PPC_BIT32(7) // Object can only be modified by signed updates
 #define PLPKS_WRAPPINGKEY	PPC_BIT32(8) // Object contains a wrapping key
 #define PLPKS_HVPROVISIONED	PPC_BIT32(28) // Hypervisor has provisioned this object
+#define PLPKS_REVOKED		PPC_BIT32(30) // Object is revoked
 
 // Signature algorithm flags from signed_update_algorithms
 #define PLPKS_ALG_RSA2048	PPC_BIT(0)
@@ -123,6 +124,20 @@ int plpks_wrap_object(u8 **input_buf, u64 input_len, u16 wrap_flags,
 
 int plpks_unwrap_object(u8 **input_buf, u64 input_len,
 			u8 **output_buf, u64 *output_len);
+
+int plpks_revoke_wrapping_key(struct plpks_var *var);
+
+int plpks_unrevoke_wrapping_key(struct plpks_var *var);
+
+int plpks_del_wrapping_key(struct plpks_var *var);
+
+int plpks_is_wrapping_key_revoked(struct plpks_var *var);
+
+int plpks_get_object_labels(u8 **output_buf, u64 *output_len,
+			    char *comp_prefix);
+
+bool plpks_revoke_is_supported(void);
+
 #else // CONFIG_PSERIES_PLPKS
 static inline bool plpks_is_available(void) { return false; }
 static inline u16 plpks_get_passwordlen(void) { BUILD_BUG(); }
diff --git a/arch/powerpc/platforms/pseries/plpks.c b/arch/powerpc/platforms/pseries/plpks.c
index b553f7b130b6..48a86497eb2b 100644
--- a/arch/powerpc/platforms/pseries/plpks.c
+++ b/arch/powerpc/platforms/pseries/plpks.c
@@ -23,8 +23,17 @@
  */
 #define PLPKS_WRAPPING_BUF_DIFF	1024
 
+/*
+ * Maximum length for the buffer to store the retrieved object labels
+ */
+#define PLPKS_OBJLABEL_BUF_MAX	2550
+
+#define PLPKS_OBJLABEL_LEN_FIELD_SIZE	2
+#define PLPKS_OBJLABEL_PREFIX_LEN	8
+
 #define PLPKS_WRAP_INTERFACE_BIT	3
 #define PLPKS_WRAPPING_KEY_LENGTH	32
+#define PLPKS_REVOKE_INTERFACE_BIT	4
 
 #define WRAPFLAG_BE_BIT_SET(be_bit) \
 	BIT_ULL(63 - (be_bit))
@@ -46,6 +55,7 @@
 #include <linux/libfdt.h>
 #include <linux/memblock.h>
 #include <linux/bitfield.h>
+#include <linux/unaligned.h>
 #include <asm/hvcall.h>
 #include <asm/machdep.h>
 #include <asm/plpks.h>
@@ -67,6 +77,7 @@ static u32 maxlargeobjectsize;
 static u64 signedupdatealgorithms;
 static u64 wrappingfeatures;
 static bool wrapsupport;
+static bool revokesupport;
 
 struct plpks_auth {
 	u8 version;
@@ -146,6 +157,9 @@ static int pseries_status_to_err(int rc)
 	case H_ABORTED:
 		err = -EIO;
 		break;
+	case H_CONTINUE:
+		err = -EAGAIN;
+		break;
 	default:
 		err = -EINVAL;
 	}
@@ -312,6 +326,7 @@ static int _plpks_get_config(void)
 	signedupdatealgorithms = be64_to_cpu(config->signedupdatealgorithms);
 	wrappingfeatures = be64_to_cpu(config->wrappingfeatures);
 	wrapsupport = config->flags & PPC_BIT8(PLPKS_WRAP_INTERFACE_BIT);
+	revokesupport = config->flags & PPC_BIT8(PLPKS_REVOKE_INTERFACE_BIT);
 
 	// Validate that the numbers we get back match the requirements of the spec
 	if (maxpwsize < 32) {
@@ -831,9 +846,6 @@ static int plpks_read_var(u8 consumer, struct plpks_var *var)
 	if (var->namelen > PLPKS_MAX_NAME_SIZE)
 		return -EINVAL;
 
-	if (var->policy & PLPKS_WRAPPINGKEY)
-		return -EPERM;
-
 	auth = construct_auth(consumer);
 	if (IS_ERR(auth))
 		return PTR_ERR(auth);
@@ -903,6 +915,23 @@ bool plpks_wrapping_is_supported(void)
 }
 EXPORT_SYMBOL_GPL(plpks_wrapping_is_supported);
 
+/**
+ * plpks_revoke_is_supported() - Get the H_PKS_REVOKE_OBJECT and
+ * H_PKS_UNREVOKE_OBJECT interfaces availability status for the LPAR.
+ *
+ * Successful execution of the H_PKS_GET_CONFIG HCALL during initialization
+ * sets bit 4 of the flags variable in the PLPKS config structure if the
+ * H_PKS_REVOKE_OBJECT and H_PKS_UNREVOKE_OBJECT interfaces are supported.
+ *
+ * Returns: true if the H_PKS_REVOKE_OBJECT and H_PKS_UNREVOKE_OBJECT interfaces
+ * are supported, false if not.
+ */
+bool plpks_revoke_is_supported(void)
+{
+	return revokesupport;
+}
+EXPORT_SYMBOL_GPL(plpks_revoke_is_supported);
+
 /**
  * plpks_gen_wrapping_key() - Generate a new random key with the 'wrapping key'
  * policy set.
@@ -1189,6 +1218,446 @@ int plpks_unwrap_object(u8 **input_buf, u64 input_len, u8 **output_buf,
 }
 EXPORT_SYMBOL_GPL(plpks_unwrap_object);
 
+/**
+ * plpks_revoke_wrapping_key() - Revoke a wrapping key stored in the PLPKS.
+ * @var: variable representing the wrapping key to be revoked
+ *
+ * The H_PKS_REVOKE_OBJECT HCALL revokes an object stored in the PLPKS.
+ *
+ * Possible reasons for the returned errno values:
+ *
+ * -ENXIO	if PLPKS is not supported
+ * -EIO		if PLPKS access is blocked due to the LPAR's state
+ *		if PLPKS modification is blocked due to the LPAR's state
+ *		if an error occurred while processing the request
+ * -EINVAL	if invalid authorization parameter
+ *		if invalid wrapping key label parameter
+ *		if invalid wrapping key label length parameter
+ *		if invalid or unsupported wrapping key revoking flags
+ * -EPERM	if access is denied
+ * -ENOENT	if the requested wrapping key was not found
+ * -EBUSY	if unable to handle the request or long running operation
+ *		initiated, retry later.
+ *
+ * Returns: On success 0 is returned, a negative errno if not.
+ */
+int plpks_revoke_wrapping_key(struct plpks_var *var)
+{
+	unsigned long retbuf[PLPAR_HCALL_BUFSIZE] = { 0 };
+	struct plpks_auth *auth = NULL;
+	struct label *label;
+	u64 objrevokeflags = 0;
+	int rc = 0, pseries_status = 0;
+
+	if (!var->name || !*var->name) {
+		pr_err("key label cannot be NULL/empty\n");
+		rc = -EINVAL;
+		goto out;
+	}
+
+	if (!strcmp((char *)var->name, PLPKS_DEFAULT_WRAPKEY_LABEL)) {
+		pr_warn("the default wrapping key must not be revoked!\n");
+		rc = -EPERM;
+		goto out;
+	}
+
+	auth = construct_auth(PLPKS_OS_OWNER);
+	if (IS_ERR(auth)) {
+		rc = PTR_ERR(auth);
+		goto out;
+	}
+
+	label = construct_label(var->component, var->os, var->name,
+				var->namelen);
+	if (IS_ERR(label)) {
+		rc = PTR_ERR(label);
+		goto out;
+	}
+
+	rc = plpar_hcall(H_PKS_REVOKE_OBJECT, retbuf, virt_to_phys(auth),
+			 virt_to_phys(label), label->size, objrevokeflags);
+
+	pseries_status = rc;
+	rc = pseries_status_to_err(rc);
+
+	if (rc) {
+		pr_err("H_PKS_REVOKE_OBJECT failed. pseries_status=%d, rc=%d\n",
+		       pseries_status, rc);
+	}
+
+	if (!rc || (rc == -EPERM && retbuf[0]))
+		var->policy = (u32)retbuf[0];
+
+	kfree(label);
+out:
+	kfree(auth);
+	return rc;
+}
+EXPORT_SYMBOL_GPL(plpks_revoke_wrapping_key);
+
+/**
+ * plpks_unrevoke_wrapping_key() - Unrevoke a revoked wrapping key in the PLPKS.
+ * @var: variable representing the revoked wrapping key to be unrevoked
+ *
+ * The H_PKS_UNREVOKE_OBJECT HCALL unrevokes a revoked object stored in the
+ * PLPKS.
+ *
+ * Possible reasons for the returned errno values:
+ *
+ * -ENXIO	if PLPKS is not supported
+ * -EIO		if PLPKS access is blocked due to the LPAR's state
+ *		if PLPKS modification is blocked due to the LPAR's state
+ *		if an error occurred while processing the request
+ * -EINVAL	if invalid authorization parameter
+ *		if invalid object label parameter
+ *		if invalid object label length parameter
+ *		if invalid or unsupported object revoking flags
+ * -EPERM	if access is denied
+ * -ENOENT	if the requested object was not found
+ * -EBUSY	if unable to handle the request or long running operation
+ *		initiated, retry later.
+ *
+ * Returns: On success 0 is returned, a negative errno if not.
+ */
+int plpks_unrevoke_wrapping_key(struct plpks_var *var)
+{
+	unsigned long retbuf[PLPAR_HCALL_BUFSIZE] = { 0 };
+	struct plpks_auth *auth = NULL;
+	struct label *label;
+	u64 objrevokeflags = 0;
+	int rc = 0, pseries_status = 0;
+
+	if (!var->name || !*var->name) {
+		pr_err("key label cannot be NULL/empty\n");
+		rc = -EINVAL;
+		goto out;
+	}
+
+	if (!strcmp((char *)var->name, PLPKS_DEFAULT_WRAPKEY_LABEL)) {
+		pr_warn("unrevoke on the default wrapping key is invalid\n");
+		rc = -EINVAL;
+		goto out;
+	}
+
+	auth = construct_auth(PLPKS_OS_OWNER);
+	if (IS_ERR(auth)) {
+		rc = PTR_ERR(auth);
+		goto out;
+	}
+
+	label = construct_label(var->component, var->os, var->name,
+				var->namelen);
+	if (IS_ERR(label)) {
+		rc = PTR_ERR(label);
+		goto out;
+	}
+
+	rc = plpar_hcall(H_PKS_UNREVOKE_OBJECT, retbuf,
+			 virt_to_phys(auth), virt_to_phys(label),
+			 label->size, objrevokeflags);
+
+	pseries_status = rc;
+	rc = pseries_status_to_err(rc);
+
+	if (rc)
+		pr_err("H_PKS_UNREVOKE_OBJECT failed. pseries_status=%d, rc=%d\n",
+		       pseries_status, rc);
+
+	if (!rc || (rc == -EPERM && retbuf[0]))
+		var->policy = (u32)retbuf[0];
+
+	kfree(label);
+out:
+	kfree(auth);
+	return rc;
+}
+EXPORT_SYMBOL_GPL(plpks_unrevoke_wrapping_key);
+
+/**
+ * plpks_is_wrapping_key_revoked() - Check if a given wrapping key has been
+ * revoked.
+ * @var: variable representing the wrapping key to be checked
+ *
+ * When the H_PKS_READ_OBJECT HCALL tries reads an object that exists but when
+ * the policy is not met, it returns H_AUTHORITY along with the 4-byte object
+ * policy. This policy is inspected to determine if the object has been revoked.
+ *
+ * Possible reasons for the returned errno values:
+ *
+ * -ENXIO	if PLPKS is not supported
+ * -EIO		if PLPKS access is blocked due to the LPAR's state
+ *		if an error occurred while processing the request
+ * -EINVAL	if invalid authorization parameter
+ *		if invalid object label parameter
+ *		if invalid object label len parameter
+ *		if invalid output data parameter
+ *		if invalid output data len parameter
+ * -EPERM	if access is denied
+ * -ENOENT	if the requested object was not found
+ * -EFBIG	if the requested object couldn't be
+ *		stored in the buffer provided
+ * -EBUSY	if unable to handle the request
+ *
+ * Returns: 1 is returned if the wrapping key has been revoked. 0 is returned if
+ *	    the wrapping key has not been revoked. Otherwise, a negative errno
+ *	    is returned.
+ */
+int plpks_is_wrapping_key_revoked(struct plpks_var *var)
+{
+	int rc;
+
+	if (!var->name || !*var->name) {
+		pr_err("key label cannot be NULL/empty\n");
+		rc = -EINVAL;
+		goto out;
+	}
+
+	rc = plpks_read_var(PLPKS_OS_OWNER, var);
+	if (!rc) {
+		pr_err("unexpected successful read of wrapping key\n");
+		rc = -EIO;
+	} else if (rc == -EPERM) {
+		if (var->policy & PLPKS_WRAPPINGKEY) {
+			if (var->policy & PLPKS_REVOKED)
+				rc = 1;
+			else
+				rc = 0;
+		}
+	}
+
+out:
+	return rc;
+}
+EXPORT_SYMBOL_GPL(plpks_is_wrapping_key_revoked);
+
+/**
+ * plpks_del_wrapping_key() - Delete a wrapping key from the PLPKS.
+ * @var: variable representing the revoked wrapping key to be deleted
+ *
+ * The plpks_remove_var function removes the specified variable and its data
+ * from the PLPKS by invoking the H_PKS_REMOVE_OBJECT HCALL.
+ *
+ * Possible reasons for the returned errno values:
+ *
+ * -ENXIO	if PLPKS is not supported
+ * -EIO		if PLPKS access is blocked due to the LPAR's state
+ *		if PLPKS modification is blocked due to the LPAR's state
+ *		if an error occurred while processing the request
+ * -EINVAL	if invalid authorization parameter
+ *		if invalid object label parameter
+ *		if invalid object label len parameter
+ * -EPERM	if access is denied
+ * -ENOENT	if the requested object was not found
+ * -EBUSY	if unable to handle the request
+ *
+ * Returns: On success 0 is returned, a negative errno if not.
+ */
+int plpks_del_wrapping_key(struct plpks_var *var)
+{
+	int rc;
+	struct plpks_var_name vname;
+
+	if (!var->name || !*var->name) {
+		pr_err("key label cannot be NULL/empty\n");
+		rc = -EINVAL;
+		goto out;
+	}
+
+	if (!strcmp((char *)var->name, PLPKS_DEFAULT_WRAPKEY_LABEL)) {
+		pr_warn("the default wrapping key must not be deleted!\n");
+		rc = -EPERM;
+		goto out;
+	}
+
+	rc = plpks_is_wrapping_key_revoked(var);
+	if (rc == 1) {
+		vname = (struct plpks_var_name) {
+			.name = var->name,
+			.namelen = var->namelen
+		};
+
+		rc = plpks_remove_var(PLPKS_WRAPKEY_COMPONENT, var->os,
+				      vname);
+		if (rc)
+			pr_err("deletion of <%s> failed. rc=%d\n",
+			       (char *)var->name, rc);
+		goto out;
+	} else if (!rc) {
+		pr_err("revoke <%s> before deletion\n", (char *)var->name);
+		rc = -EPERM;
+		goto out;
+	} else {
+		pr_err("revocation status check failed for <%s>. rc = %d\n",
+		       (char *)var->name, rc);
+	}
+
+out:
+	return rc;
+}
+EXPORT_SYMBOL_GPL(plpks_del_wrapping_key);
+
+/**
+ * plpks_get_object_labels() - retrieve a list of object labels for the objects
+ * stored in the PLPKS
+ * @output_buf: buffer to store the retrieved object labels
+ * @output_len: number of object labels retrieved
+ * @comp_prefix: component prefix string
+ *
+ * The H_PKS_GET_OBJECTLABELS HCALL retrieves a list of object labels for the
+ * objects with the given component prefix stored in the PLPKS.
+ *
+ * Possible reasons for the returned errno values:
+ *
+ * -ENXIO	if PLPKS is not supported
+ * -EIO		if PLPKS access is blocked due to the LPAR's state
+ *		if PLPKS modification is blocked due to the LPAR's state
+ *		if an error occurred while processing the request
+ * -EINVAL	if invalid authorization parameter
+ *		if invalid output buffer parameter
+ *		if invalid output buffer length parameter
+ *		if invalid continue token parameter
+ *		if the provided component prefix is NULL
+ * -EPERM	if access is denied
+ * -EBUSY	if unable to handle the request or long running operation
+ *		initiated, retry later.
+ *
+ * Returns: On success 0 is returned, a negative errno if not.
+ */
+int plpks_get_object_labels(u8 **output_buf, u64 *output_len,
+			    char *comp_prefix)
+{
+	unsigned long retbuf[PLPAR_HCALL_BUFSIZE] = { 0 };
+	u8 *labels_buf = NULL;
+	u8 *tmp_buf = NULL;
+	struct plpks_auth *auth = NULL;
+	struct label_attr *metadata = NULL;
+	u16 label_len;
+	u64 labels_count;
+	u64 continuetoken = 0, output_buf_len = 0;
+	int rc = 0, pseries_status = 0;
+	size_t labels_buf_offset = 0, output_buf_offset = 0;
+	size_t obj_label_entry_size, i;
+
+	*output_buf = NULL;
+	*output_len = 0;
+
+	if (!comp_prefix) {
+		rc = -EINVAL;
+		goto out;
+	}
+
+	auth = construct_auth(PLPKS_OS_OWNER);
+	if (IS_ERR(auth)) {
+		rc = PTR_ERR(auth);
+		goto out;
+	}
+
+	do {
+		labels_buf =
+			kzalloc(roundup_pow_of_two(PLPKS_OBJLABEL_BUF_MAX),
+				GFP_KERNEL);
+
+		if (!labels_buf) {
+			pr_err("labels_buf buffer allocation failed\n");
+			rc = -ENOMEM;
+			goto out_free_output_buf;
+		}
+
+		rc = plpar_hcall(H_PKS_GET_OBJECTLABELS, retbuf,
+				 virt_to_phys(auth), continuetoken,
+				 virt_to_phys(labels_buf),
+				 roundup_pow_of_two(PLPKS_OBJLABEL_BUF_MAX));
+
+		pseries_status = rc;
+		rc = pseries_status_to_err(rc);
+
+		if (rc && rc != -EAGAIN) {
+			pr_err("H_PKS_GET_OBJECTLABELS failed. pseries_status=%d rc=%d\n",
+			       pseries_status, rc);
+			goto out_free_labels_buf;
+		} else {
+			/*
+			 * Setting an incorrect countinuetoken upon
+			 * receiving H_CONTINUE would result in H_P2. Since
+			 * the continuetoken is being set to the expected
+			 * value from the previous call, H_P2 must not be
+			 * returned.
+			 */
+			continuetoken = retbuf[1];
+
+			labels_count = retbuf[0];
+			if (!labels_count) {
+				kfree(labels_buf);
+				labels_buf = NULL;
+				goto out;
+			}
+
+			/*
+			 * Filter out object labels that don't have the provided
+			 * component prefix.
+			 */
+
+			output_buf_len +=
+				roundup_pow_of_two(PLPKS_OBJLABEL_BUF_MAX);
+
+			tmp_buf = krealloc(*output_buf, output_buf_len,
+					   GFP_KERNEL);
+
+			if (!tmp_buf) {
+				pr_err("output buffer re-allocation failed\n");
+				rc = -ENOMEM;
+				goto out_free_labels_buf;
+			}
+
+			*output_buf = tmp_buf;
+
+			for (i = 0; i < labels_count; ++i) {
+				label_len =
+					get_unaligned_be16(labels_buf +
+							   labels_buf_offset);
+
+				obj_label_entry_size =
+					PLPKS_OBJLABEL_LEN_FIELD_SIZE +
+					label_len;
+
+				metadata =
+					(struct label_attr *)(labels_buf +
+					labels_buf_offset +
+					PLPKS_OBJLABEL_LEN_FIELD_SIZE);
+
+				if (!memcmp(metadata->prefix, comp_prefix,
+					    PLPKS_OBJLABEL_PREFIX_LEN)) {
+					memcpy(*output_buf + output_buf_offset,
+					       labels_buf + labels_buf_offset,
+					       obj_label_entry_size);
+
+					output_buf_offset +=
+						obj_label_entry_size;
+					(*output_len) += 1;
+				}
+				labels_buf_offset += obj_label_entry_size;
+			}
+			kfree(labels_buf);
+			labels_buf = NULL;
+			labels_buf_offset = 0;
+		}
+	} while (rc == -EAGAIN);
+
+	goto out;
+
+out_free_labels_buf:
+	kfree(labels_buf);
+	labels_buf = NULL;
+out_free_output_buf:
+	kfree(*output_buf);
+	*output_buf = NULL;
+	*output_len = 0;
+out:
+	kfree(auth);
+	return rc;
+}
+EXPORT_SYMBOL_GPL(plpks_get_object_labels);
+
 /**
  * plpks_read_os_var() - Fetch the data for the specified variable that is owned
  * by the OS consumer.
-- 
2.52.0