linux-kernel - [PATCH 4.4 08/46] net: emac: Fix napi poll list corruption

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Message-Id: <20171019134845.892728529@linuxfoundation.org>
Date:   Thu, 19 Oct 2017 15:48:44 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Christian Lamparter <chunkeey@...glemail.com>,
        "David S. Miller" <davem@...emloft.net>
Subject: [PATCH 4.4 08/46] net: emac: Fix napi poll list corruption

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Christian Lamparter <chunkeey@...glemail.com>

[ Upstream commit f55956065ec94e3e9371463d693a1029c4cc3007 ]

This patch is pretty much a carbon copy of
commit 3079c652141f ("caif: Fix napi poll list corruption")
with "caif" replaced by "emac".

The commit d75b1ade567f ("net: less interrupt masking in NAPI")
breaks emac.

It is now required that if the entire budget is consumed when poll
returns, the napi poll_list must remain empty.  However, like some
other drivers emac tries to do a last-ditch check and if there is
more work it will call napi_reschedule and then immediately process
some of this new work.  Should the entire budget be consumed while
processing such new work then we will violate the new caller
contract.

This patch fixes this by not touching any work when we reschedule
in emac.

Signed-off-by: Christian Lamparter <chunkeey@...glemail.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/net/ethernet/ibm/emac/mal.c |    3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

--- a/drivers/net/ethernet/ibm/emac/mal.c
+++ b/drivers/net/ethernet/ibm/emac/mal.c
@@ -402,7 +402,7 @@ static int mal_poll(struct napi_struct *
 	unsigned long flags;

 	MAL_DBG2(mal, "poll(%d)" NL, budget);
- again:
+
 	/* Process TX skbs */
 	list_for_each(l, &mal->poll_list) {
 		struct mal_commac *mc =
@@ -451,7 +451,6 @@ static int mal_poll(struct napi_struct *
 			spin_lock_irqsave(&mal->lock, flags);
 			mal_disable_eob_irq(mal);
 			spin_unlock_irqrestore(&mal->lock, flags);
-			goto again;
 		}
 		mc->ops->poll_tx(mc->dev);
 	}