[PATCH net-next 01/12] s390/qeth: don't access skb after transmission

Julian Wiedmann
2017-08-15T15:02:39Z

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 <jwi@linux.vnet.ibm.com>
Acked-by: Ursula Braun <ubraun@linux.vnet.ibm.com>
---
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++;
--
2.11.2