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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Jeff Garzik , Roland Dreier , linux-kernel@vger.kernel.org (open list) Subject: [PATCH net] net: ibm: emac: mal: fix potential system hang in mal_remove() Date: Wed, 3 Jun 2026 16:08:21 -0700 Message-ID: <20260603230821.5619-1-rosenp@gmail.com> X-Mailer: git-send-email 2.54.0 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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). Fixes: 59e90b2d2250 ("ibm_emac: Convert to use napi_struct independent of struct net_device") Assisted-by: antigravity:gemini-3.5-flash Signed-off-by: Rosen Penev --- drivers/net/ethernet/ibm/emac/mal.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/drivers/net/ethernet/ibm/emac/mal.c b/drivers/net/ethernet/ibm/emac/mal.c index 83dd7f99d8d5..74526002d52b 100644 --- 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); -- 2.54.0