[PATCH 6.1.y 2/2] pseries/plpks: fix error handling in plpks_read_var()

[Sasha Levin <sashal@kernel.org>]

From: Srish Srinivasan <ssrish@linux.ibm.com>

[ Upstream commit d52a1659cb1718f93166ab8dd8621237e564a1c4 ]

When a PLPKS variable is initialized without a policy and used to read an
object with the PLPKS_WRAPPINGKEY policy set, the hypervisor returns
H_AUTHORITY along with the object's policy. However, plpks_read_var()
currently treats this the same as any other H_AUTHORITY failure and returns
an error without propagating the policy information to the caller.

Distinguish this case from other H_AUTHORITY failures and propagate the
returned policy to the caller while preserving the authorization error.
Remove the explicit assignment of zero to rc on H_SUCCESS, as it is
redundant.

Also validate the PLPKS variable pointer before dereferencing it.

Fixes: 2454a7af0f2a ("powerpc/pseries: define driver for Platform KeyStore")
Cc: stable@vger.kernel.org # 6.0
Signed-off-by: Srish Srinivasan <ssrish@linux.ibm.com>
Tested-by: R Nageswara Sastry <rnsastry@linux.ibm.com>
Signed-off-by: Madhavan Srinivasan <maddy@linux.ibm.com>
Link: https://patch.msgid.link/20260923182816.151451-2-ssrish@linux.ibm.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 arch/powerpc/platforms/pseries/plpks.c | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/arch/powerpc/platforms/pseries/plpks.c b/arch/powerpc/platforms/pseries/plpks.c
index b66a980478fec..b15e841b19791 100644
--- a/arch/powerpc/platforms/pseries/plpks.c
+++ b/arch/powerpc/platforms/pseries/plpks.c
@@ -489,6 +489,9 @@ static int plpks_read_var(u8 consumer, struct plpks_var *var)
 	u8 *output;
 	int rc;
 
+	if (!var)
+		return -EINVAL;
+
 	if (var->namelen > PLPKS_MAX_NAME_SIZE)
 		return -EINVAL;
 
@@ -520,24 +523,23 @@ static int plpks_read_var(u8 consumer, struct plpks_var *var)
 				 virt_to_phys(var->name), var->namelen, virt_to_phys(output),
 				 maxobjsize);
 
-
 	if (rc != H_SUCCESS) {
 		pr_err("Failed to read variable %s for component %s with error %d\n",
 		       var->name, var->component, rc);
 		rc = pseries_status_to_err(rc);
-		goto out_free_output;
+		if (rc != -EPERM || !retbuf[1])
+			goto out_free_output;
+		goto out_copy_policy;
 	}
 
 	if (!var->data || var->datalen > retbuf[0])
 		var->datalen = retbuf[0];
 
-	var->policy = retbuf[1];
-
 	if (var->data)
 		memcpy(var->data, output, var->datalen);
 
-	rc = 0;
-
+out_copy_policy:
+	var->policy = retbuf[1];
 out_free_output:
 	kfree_sensitive(output);
 out_free_label:
-- 
2.53.0