firmware: arm_ffa: Fix sched-recv callback partition lookup

ffa_sched_recv_cb_update() used list_for_each_entry_safe() to search for
a matching partition and then tested the iterator against NULL. That is
not a valid end-of-list check for circular lists and can fall through
with an invalid pointer. Use a normal iterator and detect the not-found
case correctly before touching the partition state.

Fixes: be61da9 ("firmware: arm_ffa: Allow multiple UUIDs per partition to register SRI callback")
Link: https://patch.msgid.link/20260428-ffa_fixes-v2-11-8595ae450034@kernel.org
Signed-off-by: Sudeep Holla <sudeep.holla@kernel.org>

Author: Sudeep Holla

drivers/firmware/arm_ffa/driver.c

@@ -1207,7 +1207,7 @@ static int
 ffa_sched_recv_cb_update(struct ffa_device *dev, ffa_sched_recv_cb callback,
 			 void *cb_data, bool is_registration)
 {
-	struct ffa_dev_part_info *partition = NULL, *tmp;
+	struct ffa_dev_part_info *partition = NULL;
 	struct list_head *phead;
 	bool cb_valid;
 
@@ -1220,11 +1220,11 @@ ffa_sched_recv_cb_update(struct ffa_device *dev, ffa_sched_recv_cb callback,
 		return -EINVAL;
 	}
 
-	list_for_each_entry_safe(partition, tmp, phead, node)
+	list_for_each_entry(partition, phead, node)
 		if (partition->dev == dev)
 			break;
 
-	if (!partition) {
+	if (&partition->node == phead) {
 		pr_err("%s: No such partition ID 0x%x\n", __func__, dev->vm_id);
 		return -EINVAL;
 	}