igb: Guard register dump during queue setup

The register-dump sysctl is installed before iflib allocates the queue
arrays and remains visible while they are freed. Return ENXIO outside
the queue lifetime instead of dereferencing a NULL or stale array.

Sponsored by:	BBOX.io

1 files changed, 7 insertions, 0 deletions

diff --git a/sys/dev/e1000/if_em.c b/sys/dev/e1000/if_em.c
index eaaa7c5fd2f0..42e7113bff48 100644
--- a/sys/dev/e1000/if_em.c
+++ b/sys/dev/e1000/if_em.c
@@ -845,6 +845,13 @@ static int em_get_regs(SYSCTL_HANDLER_ARGS)
 	int rc;
 	uint32_t rxqid, txqid;
 
+	/*
+	 * This sysctl is registered before iflib allocates the queue arrays,
+	 * and remains registered while iflib tears them down.
+	 */
+	if (sc->rx_queues == NULL || sc->tx_queues == NULL)
+		return (ENXIO);
+
 	regs_buff = malloc(sizeof(u32) * IGB_REGS_LEN, M_DEVBUF, M_WAITOK);
 	memset(regs_buff, 0, IGB_REGS_LEN * sizeof(u32));
 	rxqid = sc->rx_queues[0].rxr.me;