From 48856286b64e4b66ec62b94e504d0b29c1ade664 Mon Sep 17 00:00:00 2001 From: Ian Campbell Date: Wed, 6 Feb 2013 23:41:35 +0000 Subject: xen/netback: shutdown the ring if it contains garbage. A buggy or malicious frontend should not be able to confuse netback. If we spot anything which is not as it should be then shutdown the device and don't try to continue with the ring in a potentially hostile state. Well behaved and non-hostile frontends will not be penalised. As well as making the existing checks for such errors fatal also add a new check that ensures that there isn't an insane number of requests on the ring (i.e. more than would fit in the ring). If the ring contains garbage then previously is was possible to loop over this insane number, getting an error each time and therefore not generating any more pending requests and therefore not exiting the loop in xen_netbk_tx_build_gops for an externded period. Also turn various netdev_dbg calls which no precipitate a fatal error into netdev_err, they are rate limited because the device is shutdown afterwards. This fixes at least one known DoS/softlockup of the backend domain. Signed-off-by: Ian Campbell Reviewed-by: Konrad Rzeszutek Wilk Acked-by: Jan Beulich Signed-off-by: David S. Miller --- drivers/net/xen-netback/common.h | 3 ++ drivers/net/xen-netback/interface.c | 23 ++++++++------ drivers/net/xen-netback/netback.c | 62 +++++++++++++++++++++++++++---------- 3 files changed, 62 insertions(+), 26 deletions(-) diff --git a/drivers/net/xen-netback/common.h b/drivers/net/xen-netback/common.h index 94b79c3338c4..9d7f1723dd8f 100644 --- a/drivers/net/xen-netback/common.h +++ b/drivers/net/xen-netback/common.h @@ -151,6 +151,9 @@ void xen_netbk_queue_tx_skb(struct xenvif *vif, struct sk_buff *skb); /* Notify xenvif that ring now has space to send an skb to the frontend */ void xenvif_notify_tx_completion(struct xenvif *vif); +/* Prevent the device from generating any further traffic. */ +void xenvif_carrier_off(struct xenvif *vif); + /* Returns number of ring slots required to send an skb to the frontend */ unsigned int xen_netbk_count_skb_slots(struct xenvif *vif, struct sk_buff *skb); diff --git a/drivers/net/xen-netback/interface.c b/drivers/net/xen-netback/interface.c index b7d41f8c338a..b8c5193bd420 100644 --- a/drivers/net/xen-netback/interface.c +++ b/drivers/net/xen-netback/interface.c @@ -343,17 +343,22 @@ err: return err; } -void xenvif_disconnect(struct xenvif *vif) +void xenvif_carrier_off(struct xenvif *vif) { struct net_device *dev = vif->dev; - if (netif_carrier_ok(dev)) { - rtnl_lock(); - netif_carrier_off(dev); /* discard queued packets */ - if (netif_running(dev)) - xenvif_down(vif); - rtnl_unlock(); - xenvif_put(vif); - } + + rtnl_lock(); + netif_carrier_off(dev); /* discard queued packets */ + if (netif_running(dev)) + xenvif_down(vif); + rtnl_unlock(); + xenvif_put(vif); +} + +void xenvif_disconnect(struct xenvif *vif) +{ + if (netif_carrier_ok(vif->dev)) + xenvif_carrier_off(vif); atomic_dec(&vif->refcnt); wait_event(vif->waiting_to_free, atomic_read(&vif->refcnt) == 0); diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c index f2d6b78d901d..c2e3336b4f98 100644 --- a/drivers/net/xen-netback/netback.c +++ b/drivers/net/xen-netback/netback.c @@ -888,6 +888,13 @@ static void netbk_tx_err(struct xenvif *vif, xenvif_put(vif); } +static void netbk_fatal_tx_err(struct xenvif *vif) +{ + netdev_err(vif->dev, "fatal error; disabling device\n"); + xenvif_carrier_off(vif); + xenvif_put(vif); +} + static int netbk_count_requests(struct xenvif *vif, struct xen_netif_tx_request *first, struct xen_netif_tx_request *txp, @@ -901,19 +908,22 @@ static int netbk_count_requests(struct xenvif *vif, do { if (frags >= work_to_do) { - netdev_dbg(vif->dev, "Need more frags\n"); + netdev_err(vif->dev, "Need more frags\n"); + netbk_fatal_tx_err(vif); return -frags; } if (unlikely(frags >= MAX_SKB_FRAGS)) { - netdev_dbg(vif->dev, "Too many frags\n"); + netdev_err(vif->dev, "Too many frags\n"); + netbk_fatal_tx_err(vif); return -frags; } memcpy(txp, RING_GET_REQUEST(&vif->tx, cons + frags), sizeof(*txp)); if (txp->size > first->size) { - netdev_dbg(vif->dev, "Frags galore\n"); + netdev_err(vif->dev, "Frag is bigger than frame.\n"); + netbk_fatal_tx_err(vif); return -frags; } @@ -921,8 +931,9 @@ static int netbk_count_requests(struct xenvif *vif, frags++; if (unlikely((txp->offset + txp->size) > PAGE_SIZE)) { - netdev_dbg(vif->dev, "txp->offset: %x, size: %u\n", + netdev_err(vif->dev, "txp->offset: %x, size: %u\n", txp->offset, txp->size); + netbk_fatal_tx_err(vif); return -frags; } } while ((txp++)->flags & XEN_NETTXF_more_data); @@ -1095,7 +1106,8 @@ static int xen_netbk_get_extras(struct xenvif *vif, do { if (unlikely(work_to_do-- <= 0)) { - netdev_dbg(vif->dev, "Missing extra info\n"); + netdev_err(vif->dev, "Missing extra info\n"); + netbk_fatal_tx_err(vif); return -EBADR; } @@ -1104,8 +1116,9 @@ static int xen_netbk_get_extras(struct xenvif *vif, if (unlikely(!extra.type || extra.type >= XEN_NETIF_EXTRA_TYPE_MAX)) { vif->tx.req_cons = ++cons; - netdev_dbg(vif->dev, + netdev_err(vif->dev, "Invalid extra type: %d\n", extra.type); + netbk_fatal_tx_err(vif); return -EINVAL; } @@ -1121,13 +1134,15 @@ static int netbk_set_skb_gso(struct xenvif *vif, struct xen_netif_extra_info *gso) { if (!gso->u.gso.size) { - netdev_dbg(vif->dev, "GSO size must not be zero.\n"); + netdev_err(vif->dev, "GSO size must not be zero.\n"); + netbk_fatal_tx_err(vif); return -EINVAL; } /* Currently only TCPv4 S.O. is supported. */ if (gso->u.gso.type != XEN_NETIF_GSO_TYPE_TCPV4) { - netdev_dbg(vif->dev, "Bad GSO type %d.\n", gso->u.gso.type); + netdev_err(vif->dev, "Bad GSO type %d.\n", gso->u.gso.type); + netbk_fatal_tx_err(vif); return -EINVAL; } @@ -1264,9 +1279,25 @@ static unsigned xen_netbk_tx_build_gops(struct xen_netbk *netbk) /* Get a netif from the list with work to do. */ vif = poll_net_schedule_list(netbk); + /* This can sometimes happen because the test of + * list_empty(net_schedule_list) at the top of the + * loop is unlocked. Just go back and have another + * look. + */ if (!vif) continue; + if (vif->tx.sring->req_prod - vif->tx.req_cons > + XEN_NETIF_TX_RING_SIZE) { + netdev_err(vif->dev, + "Impossible number of requests. " + "req_prod %d, req_cons %d, size %ld\n", + vif->tx.sring->req_prod, vif->tx.req_cons, + XEN_NETIF_TX_RING_SIZE); + netbk_fatal_tx_err(vif); + continue; + } + RING_FINAL_CHECK_FOR_REQUESTS(&vif->tx, work_to_do); if (!work_to_do) { xenvif_put(vif); @@ -1294,17 +1325,14 @@ static unsigned xen_netbk_tx_build_gops(struct xen_netbk *netbk) work_to_do = xen_netbk_get_extras(vif, extras, work_to_do); idx = vif->tx.req_cons; - if (unlikely(work_to_do < 0)) { - netbk_tx_err(vif, &txreq, idx); + if (unlikely(work_to_do < 0)) continue; - } } ret = netbk_count_requests(vif, &txreq, txfrags, work_to_do); - if (unlikely(ret < 0)) { - netbk_tx_err(vif, &txreq, idx - ret); + if (unlikely(ret < 0)) continue; - } + idx += ret; if (unlikely(txreq.size < ETH_HLEN)) { @@ -1316,11 +1344,11 @@ static unsigned xen_netbk_tx_build_gops(struct xen_netbk *netbk) /* No crossing a page as the payload mustn't fragment. */ if (unlikely((txreq.offset + txreq.size) > PAGE_SIZE)) { - netdev_dbg(vif->dev, + netdev_err(vif->dev, "txreq.offset: %x, size: %u, end: %lu\n", txreq.offset, txreq.size, (txreq.offset&~PAGE_MASK) + txreq.size); - netbk_tx_err(vif, &txreq, idx); + netbk_fatal_tx_err(vif); continue; } @@ -1348,8 +1376,8 @@ static unsigned xen_netbk_tx_build_gops(struct xen_netbk *netbk) gso = &extras[XEN_NETIF_EXTRA_TYPE_GSO - 1]; if (netbk_set_skb_gso(vif, skb, gso)) { + /* Failure in netbk_set_skb_gso is fatal. */ kfree_skb(skb); - netbk_tx_err(vif, &txreq, idx); continue; } } -- cgit v1.2.1 From 7d5145d8eb2b9791533ffe4dc003b129b9696c48 Mon Sep 17 00:00:00 2001 From: Matthew Daley Date: Wed, 6 Feb 2013 23:41:36 +0000 Subject: xen/netback: don't leak pages on failure in xen_netbk_tx_check_gop. Signed-off-by: Matthew Daley Reviewed-by: Konrad Rzeszutek Wilk Acked-by: Ian Campbell Acked-by: Jan Beulich Signed-off-by: David S. Miller --- drivers/net/xen-netback/netback.c | 38 +++++++++++++------------------------- 1 file changed, 13 insertions(+), 25 deletions(-) diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c index c2e3336b4f98..bf692df966a9 100644 --- a/drivers/net/xen-netback/netback.c +++ b/drivers/net/xen-netback/netback.c @@ -147,7 +147,8 @@ void xen_netbk_remove_xenvif(struct xenvif *vif) atomic_dec(&netbk->netfront_count); } -static void xen_netbk_idx_release(struct xen_netbk *netbk, u16 pending_idx); +static void xen_netbk_idx_release(struct xen_netbk *netbk, u16 pending_idx, + u8 status); static void make_tx_response(struct xenvif *vif, struct xen_netif_tx_request *txp, s8 st); @@ -1007,30 +1008,20 @@ static int xen_netbk_tx_check_gop(struct xen_netbk *netbk, { struct gnttab_copy *gop = *gopp; u16 pending_idx = *((u16 *)skb->data); - struct pending_tx_info *pending_tx_info = netbk->pending_tx_info; - struct xenvif *vif = pending_tx_info[pending_idx].vif; - struct xen_netif_tx_request *txp; struct skb_shared_info *shinfo = skb_shinfo(skb); int nr_frags = shinfo->nr_frags; int i, err, start; /* Check status of header. */ err = gop->status; - if (unlikely(err)) { - pending_ring_idx_t index; - index = pending_index(netbk->pending_prod++); - txp = &pending_tx_info[pending_idx].req; - make_tx_response(vif, txp, XEN_NETIF_RSP_ERROR); - netbk->pending_ring[index] = pending_idx; - xenvif_put(vif); - } + if (unlikely(err)) + xen_netbk_idx_release(netbk, pending_idx, XEN_NETIF_RSP_ERROR); /* Skip first skb fragment if it is on same page as header fragment. */ start = (frag_get_pending_idx(&shinfo->frags[0]) == pending_idx); for (i = start; i < nr_frags; i++) { int j, newerr; - pending_ring_idx_t index; pending_idx = frag_get_pending_idx(&shinfo->frags[i]); @@ -1039,16 +1030,12 @@ static int xen_netbk_tx_check_gop(struct xen_netbk *netbk, if (likely(!newerr)) { /* Had a previous error? Invalidate this fragment. */ if (unlikely(err)) - xen_netbk_idx_release(netbk, pending_idx); + xen_netbk_idx_release(netbk, pending_idx, XEN_NETIF_RSP_OKAY); continue; } /* Error on this fragment: respond to client with an error. */ - txp = &netbk->pending_tx_info[pending_idx].req; - make_tx_response(vif, txp, XEN_NETIF_RSP_ERROR); - index = pending_index(netbk->pending_prod++); - netbk->pending_ring[index] = pending_idx; - xenvif_put(vif); + xen_netbk_idx_release(netbk, pending_idx, XEN_NETIF_RSP_ERROR); /* Not the first error? Preceding frags already invalidated. */ if (err) @@ -1056,10 +1043,10 @@ static int xen_netbk_tx_check_gop(struct xen_netbk *netbk, /* First error: invalidate header and preceding fragments. */ pending_idx = *((u16 *)skb->data); - xen_netbk_idx_release(netbk, pending_idx); + xen_netbk_idx_release(netbk, pending_idx, XEN_NETIF_RSP_OKAY); for (j = start; j < i; j++) { pending_idx = frag_get_pending_idx(&shinfo->frags[j]); - xen_netbk_idx_release(netbk, pending_idx); + xen_netbk_idx_release(netbk, pending_idx, XEN_NETIF_RSP_OKAY); } /* Remember the error: invalidate all subsequent fragments. */ @@ -1093,7 +1080,7 @@ static void xen_netbk_fill_frags(struct xen_netbk *netbk, struct sk_buff *skb) /* Take an extra reference to offset xen_netbk_idx_release */ get_page(netbk->mmap_pages[pending_idx]); - xen_netbk_idx_release(netbk, pending_idx); + xen_netbk_idx_release(netbk, pending_idx, XEN_NETIF_RSP_OKAY); } } @@ -1476,7 +1463,7 @@ static void xen_netbk_tx_submit(struct xen_netbk *netbk) txp->size -= data_len; } else { /* Schedule a response immediately. */ - xen_netbk_idx_release(netbk, pending_idx); + xen_netbk_idx_release(netbk, pending_idx, XEN_NETIF_RSP_OKAY); } if (txp->flags & XEN_NETTXF_csum_blank) @@ -1528,7 +1515,8 @@ static void xen_netbk_tx_action(struct xen_netbk *netbk) xen_netbk_tx_submit(netbk); } -static void xen_netbk_idx_release(struct xen_netbk *netbk, u16 pending_idx) +static void xen_netbk_idx_release(struct xen_netbk *netbk, u16 pending_idx, + u8 status) { struct xenvif *vif; struct pending_tx_info *pending_tx_info; @@ -1542,7 +1530,7 @@ static void xen_netbk_idx_release(struct xen_netbk *netbk, u16 pending_idx) vif = pending_tx_info->vif; - make_tx_response(vif, &pending_tx_info->req, XEN_NETIF_RSP_OKAY); + make_tx_response(vif, &pending_tx_info->req, status); index = pending_index(netbk->pending_prod++); netbk->pending_ring[index] = pending_idx; -- cgit v1.2.1 From 4cc7c1cb7b11b6f3515bd9075527576a1eecc4aa Mon Sep 17 00:00:00 2001 From: Ian Campbell Date: Wed, 6 Feb 2013 23:41:37 +0000 Subject: xen/netback: free already allocated memory on failure in xen_netbk_get_requests Signed-off-by: Ian Campbell Signed-off-by: David S. Miller --- drivers/net/xen-netback/netback.c | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-) diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c index bf692df966a9..dcb2d4d3c3ea 100644 --- a/drivers/net/xen-netback/netback.c +++ b/drivers/net/xen-netback/netback.c @@ -978,7 +978,7 @@ static struct gnttab_copy *xen_netbk_get_requests(struct xen_netbk *netbk, pending_idx = netbk->pending_ring[index]; page = xen_netbk_alloc_page(netbk, skb, pending_idx); if (!page) - return NULL; + goto err; gop->source.u.ref = txp->gref; gop->source.domid = vif->domid; @@ -1000,6 +1000,17 @@ static struct gnttab_copy *xen_netbk_get_requests(struct xen_netbk *netbk, } return gop; +err: + /* Unwind, freeing all pages and sending error responses. */ + while (i-- > start) { + xen_netbk_idx_release(netbk, frag_get_pending_idx(&frags[i]), + XEN_NETIF_RSP_ERROR); + } + /* The head too, if necessary. */ + if (start) + xen_netbk_idx_release(netbk, pending_idx, XEN_NETIF_RSP_ERROR); + + return NULL; } static int xen_netbk_tx_check_gop(struct xen_netbk *netbk, -- cgit v1.2.1 From b9149729ebdcfce63f853aa54a404c6a8f6ebbf3 Mon Sep 17 00:00:00 2001 From: Ian Campbell Date: Wed, 6 Feb 2013 23:41:38 +0000 Subject: netback: correct netbk_tx_err to handle wrap around. Signed-off-by: Ian Campbell Acked-by: Jan Beulich Signed-off-by: David S. Miller --- drivers/net/xen-netback/netback.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c index dcb2d4d3c3ea..2b9520c46e97 100644 --- a/drivers/net/xen-netback/netback.c +++ b/drivers/net/xen-netback/netback.c @@ -880,7 +880,7 @@ static void netbk_tx_err(struct xenvif *vif, do { make_tx_response(vif, txp, XEN_NETIF_RSP_ERROR); - if (cons >= end) + if (cons == end) break; txp = RING_GET_REQUEST(&vif->tx, cons++); } while (1); -- cgit v1.2.1