From 2475b22526d70234ecfe4a1ff88aed69badefba9 Mon Sep 17 00:00:00 2001 From: Ross Lagerwall Date: Mon, 3 Aug 2015 15:38:03 +0100 Subject: xen-netback: Allocate fraglist early to avoid complex rollback Determine if a fraglist is needed in the tx path, and allocate it if necessary before setting up the copy and map operations. Otherwise, undoing the copy and map operations is tricky. This fixes a use-after-free: if allocating the fraglist failed, the copy and map operations that had been set up were still executed, writing over the data area of a freed skb. Signed-off-by: Ross Lagerwall Signed-off-by: David S. Miller --- drivers/net/xen-netback/netback.c | 61 +++++++++++++++++++++------------------ 1 file changed, 33 insertions(+), 28 deletions(-) (limited to 'drivers/net/xen-netback') diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c index 7d50711476fe..1b406e706a01 100644 --- a/drivers/net/xen-netback/netback.c +++ b/drivers/net/xen-netback/netback.c @@ -810,23 +810,17 @@ static inline struct sk_buff *xenvif_alloc_skb(unsigned int size) static struct gnttab_map_grant_ref *xenvif_get_requests(struct xenvif_queue *queue, struct sk_buff *skb, struct xen_netif_tx_request *txp, - struct gnttab_map_grant_ref *gop) + struct gnttab_map_grant_ref *gop, + unsigned int frag_overflow, + struct sk_buff *nskb) { struct skb_shared_info *shinfo = skb_shinfo(skb); skb_frag_t *frags = shinfo->frags; u16 pending_idx = XENVIF_TX_CB(skb)->pending_idx; int start; pending_ring_idx_t index; - unsigned int nr_slots, frag_overflow = 0; + unsigned int nr_slots; - /* At this point shinfo->nr_frags is in fact the number of - * slots, which can be as large as XEN_NETBK_LEGACY_SLOTS_MAX. - */ - if (shinfo->nr_frags > MAX_SKB_FRAGS) { - frag_overflow = shinfo->nr_frags - MAX_SKB_FRAGS; - BUG_ON(frag_overflow > MAX_SKB_FRAGS); - shinfo->nr_frags = MAX_SKB_FRAGS; - } nr_slots = shinfo->nr_frags; /* Skip first skb fragment if it is on same page as header fragment. */ @@ -841,13 +835,6 @@ static struct gnttab_map_grant_ref *xenvif_get_requests(struct xenvif_queue *que } if (frag_overflow) { - struct sk_buff *nskb = xenvif_alloc_skb(0); - if (unlikely(nskb == NULL)) { - if (net_ratelimit()) - netdev_err(queue->vif->dev, - "Can't allocate the frag_list skb.\n"); - return NULL; - } shinfo = skb_shinfo(nskb); frags = shinfo->frags; @@ -1175,9 +1162,10 @@ static void xenvif_tx_build_gops(struct xenvif_queue *queue, unsigned *copy_ops, unsigned *map_ops) { - struct gnttab_map_grant_ref *gop = queue->tx_map_ops, *request_gop; - struct sk_buff *skb; + struct gnttab_map_grant_ref *gop = queue->tx_map_ops; + struct sk_buff *skb, *nskb; int ret; + unsigned int frag_overflow; while (skb_queue_len(&queue->tx_queue) < budget) { struct xen_netif_tx_request txreq; @@ -1265,6 +1253,29 @@ static void xenvif_tx_build_gops(struct xenvif_queue *queue, break; } + skb_shinfo(skb)->nr_frags = ret; + if (data_len < txreq.size) + skb_shinfo(skb)->nr_frags++; + /* At this point shinfo->nr_frags is in fact the number of + * slots, which can be as large as XEN_NETBK_LEGACY_SLOTS_MAX. + */ + frag_overflow = 0; + nskb = NULL; + if (skb_shinfo(skb)->nr_frags > MAX_SKB_FRAGS) { + frag_overflow = skb_shinfo(skb)->nr_frags - MAX_SKB_FRAGS; + BUG_ON(frag_overflow > MAX_SKB_FRAGS); + skb_shinfo(skb)->nr_frags = MAX_SKB_FRAGS; + nskb = xenvif_alloc_skb(0); + if (unlikely(nskb == NULL)) { + kfree_skb(skb); + xenvif_tx_err(queue, &txreq, idx); + if (net_ratelimit()) + netdev_err(queue->vif->dev, + "Can't allocate the frag_list skb.\n"); + break; + } + } + if (extras[XEN_NETIF_EXTRA_TYPE_GSO - 1].type) { struct xen_netif_extra_info *gso; gso = &extras[XEN_NETIF_EXTRA_TYPE_GSO - 1]; @@ -1272,6 +1283,7 @@ static void xenvif_tx_build_gops(struct xenvif_queue *queue, if (xenvif_set_skb_gso(queue->vif, skb, gso)) { /* Failure in xenvif_set_skb_gso is fatal. */ kfree_skb(skb); + kfree_skb(nskb); break; } } @@ -1294,9 +1306,7 @@ static void xenvif_tx_build_gops(struct xenvif_queue *queue, (*copy_ops)++; - skb_shinfo(skb)->nr_frags = ret; if (data_len < txreq.size) { - skb_shinfo(skb)->nr_frags++; frag_set_pending_idx(&skb_shinfo(skb)->frags[0], pending_idx); xenvif_tx_create_map_op(queue, pending_idx, &txreq, gop); @@ -1310,13 +1320,8 @@ static void xenvif_tx_build_gops(struct xenvif_queue *queue, queue->pending_cons++; - request_gop = xenvif_get_requests(queue, skb, txfrags, gop); - if (request_gop == NULL) { - kfree_skb(skb); - xenvif_tx_err(queue, &txreq, idx); - break; - } - gop = request_gop; + gop = xenvif_get_requests(queue, skb, txfrags, gop, + frag_overflow, nskb); __skb_queue_tail(&queue->tx_queue, skb); -- cgit v1.2.3 From 57b229063ae6dc65036209018dc7f4290cc026bb Mon Sep 17 00:00:00 2001 From: Ross Lagerwall Date: Tue, 4 Aug 2015 15:40:59 +0100 Subject: xen/netback: Wake dealloc thread after completing zerocopy work Waking the dealloc thread before decrementing inflight_packets is racy because it means the thread may go to sleep before inflight_packets is decremented. If kthread_stop() has already been called, the dealloc thread may wait forever with nothing to wake it. Instead, wake the thread only after decrementing inflight_packets. Signed-off-by: Ross Lagerwall Signed-off-by: David S. Miller --- drivers/net/xen-netback/interface.c | 6 ++++++ drivers/net/xen-netback/netback.c | 1 - 2 files changed, 6 insertions(+), 1 deletion(-) (limited to 'drivers/net/xen-netback') diff --git a/drivers/net/xen-netback/interface.c b/drivers/net/xen-netback/interface.c index 1a83e190fc15..28577a31549d 100644 --- a/drivers/net/xen-netback/interface.c +++ b/drivers/net/xen-netback/interface.c @@ -61,6 +61,12 @@ void xenvif_skb_zerocopy_prepare(struct xenvif_queue *queue, void xenvif_skb_zerocopy_complete(struct xenvif_queue *queue) { atomic_dec(&queue->inflight_packets); + + /* Wake the dealloc thread _after_ decrementing inflight_packets so + * that if kthread_stop() has already been called, the dealloc thread + * does not wait forever with nothing to wake it. + */ + wake_up(&queue->dealloc_wq); } int xenvif_schedulable(struct xenvif *vif) diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c index 1b406e706a01..3f44b522b831 100644 --- a/drivers/net/xen-netback/netback.c +++ b/drivers/net/xen-netback/netback.c @@ -1541,7 +1541,6 @@ void xenvif_zerocopy_callback(struct ubuf_info *ubuf, bool zerocopy_success) smp_wmb(); queue->dealloc_prod++; } while (ubuf); - wake_up(&queue->dealloc_wq); spin_unlock_irqrestore(&queue->callback_lock, flags); if (likely(zerocopy_success)) -- cgit v1.2.3