net: ibm: emac: mal: fix potential system hang in mal_remove()

napi_disable() is not idempotent and calling it on an already-disabled
or unenabled NAPI context will cause the kernel to spin indefinitely
waiting for the NAPI_STATE_SCHED bit to clear.

In mal_remove(), napi_disable() is called unconditionally. If no MACs were
registered, NAPI was never enabled. Also, if they were registered but
subsequently unregistered, NAPI was already disabled in
mal_unregister_commac(). In either case, calling napi_disable() causes
the kernel to hang upon module removal.

Fix this by only calling napi_disable() in mal_remove() if the commac list
is not empty (which implies NAPI is enabled).

Signed-off-by: Rosen Penev <rosenp@gmail.com>
Link: https://patch.msgid.link/20260603230821.5619-1-rosenp@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/drivers/net/ethernet/ibm/emac/mal.c b/drivers/net/ethernet/ibm/emac/mal.c
index 83dd7f99d8d524100315b4e27a769881078566f2..74526002d52bdf423793f8880d6ccf0f40636577 100644 (file)
--- a/drivers/net/ethernet/ibm/emac/mal.c
+++ b/drivers/net/ethernet/ibm/emac/mal.c
@@ -712,13 +712,13 @@ static void mal_remove(struct platform_device *ofdev)
        MAL_DBG(mal, "remove" NL);
 
        /* Synchronize with scheduled polling */
-       napi_disable(&mal->napi);
-
-       if (!list_empty(&mal->list))
+       if (!list_empty(&mal->list)) {
+               napi_disable(&mal->napi);
                /* This is *very* bad */
                WARN(1, KERN_EMERG
                       "mal%d: commac list is not empty on remove!\n",
                       mal->index);
+       }
 
        mal_reset(mal);