[PATCH 6.0 065/157] net: mana: Fix race on per-CQ variable napi work_done

Greg Kroah-Hartman
2022-12-12T13:43:11Z

From: Haiyang Zhang <haiyangz@microsoft.com>

commit 18010ff776fa42340efc428b3ea6d19b3e7c7b21 upstream.

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: e1b5683ff62e ("net: mana: Move NAPI from EQ to CQ")
Signed-off-by: Haiyang Zhang <haiyangz@microsoft.com>
Link: https://lore.kernel.org/r/1670010190-28595-1-git-send-email-haiyangz@microsoft.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/net/ethernet/microsoft/mana/gdma.h | 9 ++++++++-
drivers/net/ethernet/microsoft/mana/mana_en.c | 16 +++++++++++-----
2 files changed, 19 insertions(+), 6 deletions(-)

--- a/drivers/net/ethernet/microsoft/mana/gdma.h
+++ b/drivers/net/ethernet/microsoft/mana/gdma.h
@@ -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

--- a/drivers/net/ethernet/microsoft/mana/mana_en.c
+++ b/drivers/net/ethernet/microsoft/mana/mana_en.c
@@ -1303,10 +1303,11 @@ static void mana_poll_rx_cq(struct mana_
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 *contex
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)