From 886e1974dcc5866cbc3d133d1f3d2cc26af68cfc Mon Sep 17 00:00:00 2001 From: Julian Wiedmann Date: Tue, 15 Aug 2017 17:02:39 +0200 Subject: [PATCH] s390/qeth: don't access skb after transmission After transmitting a skb via send_packet[_fast](), the statistics code accesses the skb once more to account for transmitted page frags. This has a (theoretical?) race against the TX completion - if the TX completion is processed and frees the skb before hard_start_xmit() gets to the statistics part, we access random memory. Fix this by caching the # of page frags, before the skb is transmitted. Signed-off-by: Julian Wiedmann Acked-by: Ursula Braun Signed-off-by: David S. Miller --- drivers/s390/net/qeth_l2_main.c | 14 ++++++-------- drivers/s390/net/qeth_l3_main.c | 4 ++-- 2 files changed, 8 insertions(+), 10 deletions(-) diff --git a/drivers/s390/net/qeth_l2_main.c b/drivers/s390/net/qeth_l2_main.c index ad110abfdd47..28c9a7eda507 100644 --- a/drivers/s390/net/qeth_l2_main.c +++ b/drivers/s390/net/qeth_l2_main.c @@ -707,7 +707,7 @@ static netdev_tx_t qeth_l2_hard_start_xmit(struct sk_buff *skb, int data_offset = -1; int elements_needed = 0; int hd_len = 0; - int nr_frags; + unsigned int nr_frags; if (card->qdio.do_prio_queueing || (cast_type && card->info.is_multicast_different)) @@ -747,6 +747,7 @@ static netdev_tx_t qeth_l2_hard_start_xmit(struct sk_buff *skb, if (lin_rc) goto tx_drop; } + nr_frags = skb_shinfo(new_skb)->nr_frags; if (card->info.type == QETH_CARD_TYPE_OSN) hdr = (struct qeth_hdr *)skb->data; @@ -799,13 +800,10 @@ static netdev_tx_t qeth_l2_hard_start_xmit(struct sk_buff *skb, if (!rc) { card->stats.tx_packets++; card->stats.tx_bytes += tx_bytes; - if (card->options.performance_stats) { - nr_frags = skb_shinfo(new_skb)->nr_frags; - if (nr_frags) { - card->perf_stats.sg_skbs_sent++; - /* nr_frags + skb->data */ - card->perf_stats.sg_frags_sent += nr_frags + 1; - } + if (card->options.performance_stats && nr_frags) { + card->perf_stats.sg_skbs_sent++; + /* nr_frags + skb->data */ + card->perf_stats.sg_frags_sent += nr_frags + 1; } if (new_skb != skb) dev_kfree_skb_any(skb); diff --git a/drivers/s390/net/qeth_l3_main.c b/drivers/s390/net/qeth_l3_main.c index d42e758518ed..6648f02d61ea 100644 --- a/drivers/s390/net/qeth_l3_main.c +++ b/drivers/s390/net/qeth_l3_main.c @@ -2650,7 +2650,7 @@ static netdev_tx_t qeth_l3_hard_start_xmit(struct sk_buff *skb, int tx_bytes = skb->len; bool use_tso; int data_offset = -1; - int nr_frags; + unsigned int nr_frags; if (((card->info.type == QETH_CARD_TYPE_IQD) && (((card->options.cq != QETH_CQ_ENABLED) && !ipv) || @@ -2727,6 +2727,7 @@ static netdev_tx_t qeth_l3_hard_start_xmit(struct sk_buff *skb, if (lin_rc) goto tx_drop; } + nr_frags = skb_shinfo(new_skb)->nr_frags; if (use_tso) { hdr = skb_push(new_skb, sizeof(struct qeth_hdr_tso)); @@ -2786,7 +2787,6 @@ static netdev_tx_t qeth_l3_hard_start_xmit(struct sk_buff *skb, if (new_skb != skb) dev_kfree_skb_any(skb); if (card->options.performance_stats) { - nr_frags = skb_shinfo(new_skb)->nr_frags; if (use_tso) { card->perf_stats.large_send_bytes += tx_bytes; card->perf_stats.large_send_cnt++; -- 2.20.1