Commit 18010ff7 authored by Haiyang Zhang's avatar Haiyang Zhang Committed by Paolo Abeni
Browse files

net: mana: Fix race on per-CQ variable napi work_done 



After calling napi_complete_done(), the NAPIF_STATE_SCHED bit may be
cleared, and another CPU can start napi thread and access per-CQ variable,
cq->work_done. If the other thread (for example, from busy_poll) sets
it to a value >= budget, this thread will continue to run when it should
stop, and cause memory corruption and panic.

To fix this issue, save the per-CQ work_done variable in a local variable
before napi_complete_done(), so it won't be corrupted by a possible
concurrent thread after napi_complete_done().

Also, add a flag bit to advertise to the NIC firmware: the NAPI work_done
variable race is fixed, so the driver is able to reliably support features
like busy_poll.

Cc: stable@vger.kernel.org
Fixes: e1b5683f ("net: mana: Move NAPI from EQ to CQ")
Signed-off-by: default avatarHaiyang Zhang <haiyangz@microsoft.com>
Link: https://lore.kernel.org/r/1670010190-28595-1-git-send-email-haiyangz@microsoft.com


Signed-off-by: default avatarPaolo Abeni <pabeni@redhat.com>
parent 61d4f140

drivers/net/ethernet/microsoft/mana/gdma.h

+8 −1
Original line number Diff line number Diff line
@@ -498,7 +498,14 @@ enum { 


#define GDMA_DRV_CAP_FLAG_1_EQ_SHARING_MULTI_VPORT BIT(0)



#define GDMA_DRV_CAP_FLAGS1 GDMA_DRV_CAP_FLAG_1_EQ_SHARING_MULTI_VPORT

/* Advertise to the NIC firmware: the NAPI work_done variable race is fixed,

 * so the driver is able to reliably support features like busy_poll.

 */

#define GDMA_DRV_CAP_FLAG_1_NAPI_WKDONE_FIX BIT(2)



#define GDMA_DRV_CAP_FLAGS1 \

	(GDMA_DRV_CAP_FLAG_1_EQ_SHARING_MULTI_VPORT | \

	 GDMA_DRV_CAP_FLAG_1_NAPI_WKDONE_FIX)



#define GDMA_DRV_CAP_FLAGS2 0

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

+11 −5
Original line number Diff line number Diff line
@@ -1303,10 +1303,11 @@ static void mana_poll_rx_cq(struct mana_cq *cq) 
		xdp_do_flush();

}



static void mana_cq_handler(void *context, struct gdma_queue *gdma_queue)

static int mana_cq_handler(void *context, struct gdma_queue *gdma_queue)

{

	struct mana_cq *cq = context;

	u8 arm_bit;

	int w;



	WARN_ON_ONCE(cq->gdma_cq != gdma_queue);
@@ -1315,26 +1316,31 @@ static void mana_cq_handler(void *context, struct gdma_queue *gdma_queue) 
	else

		mana_poll_tx_cq(cq);



	if (cq->work_done < cq->budget &&

	    napi_complete_done(&cq->napi, cq->work_done)) {

	w = cq->work_done;



	if (w < cq->budget &&

	    napi_complete_done(&cq->napi, w)) {

		arm_bit = SET_ARM_BIT;

	} else {

		arm_bit = 0;

	}



	mana_gd_ring_cq(gdma_queue, arm_bit);



	return w;

}



static int mana_poll(struct napi_struct *napi, int budget)

{

	struct mana_cq *cq = container_of(napi, struct mana_cq, napi);

	int w;



	cq->work_done = 0;

	cq->budget = budget;



	mana_cq_handler(cq, cq->gdma_cq);

	w = mana_cq_handler(cq, cq->gdma_cq);



	return min(cq->work_done, budget);

	return min(w, budget);

}



static void mana_schedule_napi(void *context, struct gdma_queue *gdma_queue)