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Merge branch 'netback'
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Ian Campbell says:

====================
The Xen netback implementation contains a couple of flaws which can
allow a guest to cause a DoS in the backend domain, potentially
affecting other domains in the system.

CVE-2013-0216 is a failure to sanity check the ring producer/consumer
pointers which can allow a guest to cause netback to loop for an
extended period preventing other work from occurring.

CVE-2013-0217 is a memory leak on an error path which is guest
triggerable.

The following series contains the fixes for these issues, as previously
included in Xen Security Advisory 39:
http://lists.xen.org/archives/html/xen-announce/2013-02/msg00001.html

Changes in v2:
 - Typo and block comment format fixes
 - Added stable Cc
====================

Signed-off-by: David S. Miller <[email protected]>
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@davem330
davem330 committed Feb 8, 2013
2 parents e21b9d0 + b914972 commit 0c35565
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Showing 3 changed files with 88 additions and 53 deletions.
3 changes: 3 additions & 0 deletions drivers/net/xen-netback/common.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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);

Expand Down
23 changes: 14 additions & 9 deletions drivers/net/xen-netback/interface.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -343,17 +343,22 @@ int xenvif_connect(struct xenvif *vif, unsigned long tx_ring_ref,
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);
Expand Down
115 changes: 71 additions & 44 deletions drivers/net/xen-netback/netback.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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);
Expand Down Expand Up @@ -879,7 +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);
Expand All @@ -888,6 +889,13 @@ 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,
Expand All @@ -901,28 +909,32 @@ 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;
}

first->size -= txp->size;
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);
Expand Down Expand Up @@ -966,7 +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;
Expand All @@ -988,6 +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,
Expand All @@ -996,30 +1019,20 @@ 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]);

Expand All @@ -1028,27 +1041,23 @@ 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)
continue;

/* 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. */
Expand Down Expand Up @@ -1082,7 +1091,7 @@ 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);
}
}

Expand All @@ -1095,7 +1104,8 @@ 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;
}

Expand All @@ -1104,8 +1114,9 @@ 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;
}

Expand All @@ -1121,13 +1132,15 @@ 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;
}

Expand Down Expand Up @@ -1264,9 +1277,25 @@ 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);
Expand Down Expand Up @@ -1294,17 +1323,14 @@ 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)) {
Expand All @@ -1316,11 +1342,11 @@ 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;
}

Expand Down Expand Up @@ -1348,8 +1374,8 @@ 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;
}
}
Expand Down Expand Up @@ -1448,7 +1474,7 @@ 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)
Expand Down Expand Up @@ -1500,7 +1526,8 @@ 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;
Expand All @@ -1514,7 +1541,7 @@ 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;
Expand Down

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