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Subject[RFC PATCH 3/3] xen/netback: Fix grant copy across page boundary with KASAN
Date
From: Ross Lagerwall <ross.lagerwall@citrix.com>

When KASAN (or SLUB_DEBUG) is turned on, the normal expectation that
allocations are aligned to the next power of 2 of the size does not
hold. Therefore, handle grant copies that cross page boundaries.

Signed-off-by: Ross Lagerwall <ross.lagerwall@citrix.com>
Signed-off-by: Sergey Dyasli <sergey.dyasli@citrix.com>
---
drivers/net/xen-netback/common.h | 2 +-
drivers/net/xen-netback/netback.c | 55 ++++++++++++++++++++++++-------
2 files changed, 45 insertions(+), 12 deletions(-)

diff --git a/drivers/net/xen-netback/common.h b/drivers/net/xen-netback/common.h
index 05847eb91a1b..e57684415edd 100644
--- a/drivers/net/xen-netback/common.h
+++ b/drivers/net/xen-netback/common.h
@@ -155,7 +155,7 @@ struct xenvif_queue { /* Per-queue data for xenvif */
struct pending_tx_info pending_tx_info[MAX_PENDING_REQS];
grant_handle_t grant_tx_handle[MAX_PENDING_REQS];

- struct gnttab_copy tx_copy_ops[MAX_PENDING_REQS];
+ struct gnttab_copy tx_copy_ops[MAX_PENDING_REQS * 2];
struct gnttab_map_grant_ref tx_map_ops[MAX_PENDING_REQS];
struct gnttab_unmap_grant_ref tx_unmap_ops[MAX_PENDING_REQS];
/* passed to gnttab_[un]map_refs with pages under (un)mapping */
diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c
index 0020b2e8c279..1541b6e0cc62 100644
--- a/drivers/net/xen-netback/netback.c
+++ b/drivers/net/xen-netback/netback.c
@@ -320,6 +320,7 @@ static int xenvif_count_requests(struct xenvif_queue *queue,

struct xenvif_tx_cb {
u16 pending_idx;
+ u8 copies;
};

#define XENVIF_TX_CB(skb) ((struct xenvif_tx_cb *)(skb)->cb)
@@ -439,6 +440,7 @@ static int xenvif_tx_check_gop(struct xenvif_queue *queue,
{
struct gnttab_map_grant_ref *gop_map = *gopp_map;
u16 pending_idx = XENVIF_TX_CB(skb)->pending_idx;
+ u8 copies = XENVIF_TX_CB(skb)->copies;
/* This always points to the shinfo of the skb being checked, which
* could be either the first or the one on the frag_list
*/
@@ -450,23 +452,27 @@ static int xenvif_tx_check_gop(struct xenvif_queue *queue,
int nr_frags = shinfo->nr_frags;
const bool sharedslot = nr_frags &&
frag_get_pending_idx(&shinfo->frags[0]) == pending_idx;
- int i, err;
+ int i, err = 0;

- /* Check status of header. */
- err = (*gopp_copy)->status;
- if (unlikely(err)) {
- if (net_ratelimit())
- netdev_dbg(queue->vif->dev,
+ while (copies) {
+ /* Check status of header. */
+ int newerr = (*gopp_copy)->status;
+ if (unlikely(newerr)) {
+ if (net_ratelimit())
+ netdev_dbg(queue->vif->dev,
"Grant copy of header failed! status: %d pending_idx: %u ref: %u\n",
(*gopp_copy)->status,
pending_idx,
(*gopp_copy)->source.u.ref);
- /* The first frag might still have this slot mapped */
- if (!sharedslot)
- xenvif_idx_release(queue, pending_idx,
- XEN_NETIF_RSP_ERROR);
+ /* The first frag might still have this slot mapped */
+ if (!sharedslot && !err)
+ xenvif_idx_release(queue, pending_idx,
+ XEN_NETIF_RSP_ERROR);
+ err = newerr;
+ }
+ (*gopp_copy)++;
+ copies--;
}
- (*gopp_copy)++;

check_frags:
for (i = 0; i < nr_frags; i++, gop_map++) {
@@ -910,6 +916,7 @@ static void xenvif_tx_build_gops(struct xenvif_queue *queue,
xenvif_tx_err(queue, &txreq, extra_count, idx);
break;
}
+ XENVIF_TX_CB(skb)->copies = 0;

skb_shinfo(skb)->nr_frags = ret;
if (data_len < txreq.size)
@@ -933,6 +940,7 @@ static void xenvif_tx_build_gops(struct xenvif_queue *queue,
"Can't allocate the frag_list skb.\n");
break;
}
+ XENVIF_TX_CB(nskb)->copies = 0;
}

if (extras[XEN_NETIF_EXTRA_TYPE_GSO - 1].type) {
@@ -990,6 +998,31 @@ static void xenvif_tx_build_gops(struct xenvif_queue *queue,

queue->tx_copy_ops[*copy_ops].len = data_len;
queue->tx_copy_ops[*copy_ops].flags = GNTCOPY_source_gref;
+ XENVIF_TX_CB(skb)->copies++;
+
+ if (offset_in_page(skb->data) + data_len > XEN_PAGE_SIZE) {
+ unsigned int extra_len = offset_in_page(skb->data) +
+ data_len - XEN_PAGE_SIZE;
+
+ queue->tx_copy_ops[*copy_ops].len -= extra_len;
+ (*copy_ops)++;
+
+ queue->tx_copy_ops[*copy_ops].source.u.ref = txreq.gref;
+ queue->tx_copy_ops[*copy_ops].source.domid =
+ queue->vif->domid;
+ queue->tx_copy_ops[*copy_ops].source.offset =
+ txreq.offset + data_len - extra_len;
+
+ queue->tx_copy_ops[*copy_ops].dest.u.gmfn =
+ virt_to_gfn(skb->data + data_len - extra_len);
+ queue->tx_copy_ops[*copy_ops].dest.domid = DOMID_SELF;
+ queue->tx_copy_ops[*copy_ops].dest.offset = 0;
+
+ queue->tx_copy_ops[*copy_ops].len = extra_len;
+ queue->tx_copy_ops[*copy_ops].flags = GNTCOPY_source_gref;
+
+ XENVIF_TX_CB(skb)->copies++;
+ }

(*copy_ops)++;

--
2.17.1
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