net: mana: Guard mana_remove against double invocation

If PM resume fails (e.g., mana_attach() returns an error), mana_probe()
calls mana_remove(), which tears down the device and sets
gd->gdma_context = NULL and gd->driver_data = NULL.

However, a failed resume callback does not automatically unbind the
driver. When the device is eventually unbound, mana_remove() is invoked
a second time. Without a NULL check, it dereferences gc->dev with
gc == NULL, causing a kernel panic.

Add an early return if gdma_context or driver_data is NULL so the second
invocation is harmless. Move the dev = gc->dev assignment after the
guard so it cannot dereference NULL.

Fixes: 635096a ("net: mana: Support hibernation and kexec")
Signed-off-by: Erni Sri Satya Vennela <ernis@linux.microsoft.com>
Link: https://patch.msgid.link/20260420124741.1056179-4-ernis@linux.microsoft.com
Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

Author: Erni Sri Satya Vennela

drivers/net/ethernet/microsoft/mana/mana_en.c

@@ -3731,11 +3731,16 @@ void mana_remove(struct gdma_dev *gd, bool suspending)
 	struct gdma_context *gc = gd->gdma_context;
 	struct mana_context *ac = gd->driver_data;
 	struct mana_port_context *apc;
-	struct device *dev = gc->dev;
+	struct device *dev;
 	struct net_device *ndev;
 	int err;
 	int i;
 
+	if (!gc || !ac)
+		return;
+
+	dev = gc->dev;
+
 	disable_work_sync(&ac->link_change_work);
 	cancel_delayed_work_sync(&ac->gf_stats_work);