[PATCH 3.15 077/109] xen-netback: Fix releasing header slot on error path

Greg Kroah-Hartman
2014-07-26T19:02:39Z

From: Zoltan Kiss <zoltan.kiss@citrix.com>

[ Upstream commit 1b860da0404a76af8533099ffe0a965490939369 ]

This patch makes this function aware that the first frag and the header might
share the same ring slot. That could happen if the first slot is bigger than
PKT_PROT_LEN. Due to this the error path might release that slot twice or never,
depending on the error scenario.
xenvif_idx_release is also removed from xenvif_idx_unmap, and called separately.

Signed-off-by: Zoltan Kiss <zoltan.kiss@citrix.com>
Reported-by: Armin Zentai <armin.zentai@ezit.hu>
Cc: netdev@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: xen-devel@lists.xenproject.org
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/net/xen-netback/netback.c | 38 +++++++++++++++++++++++++++++++++-----
1 file changed, 33 insertions(+), 5 deletions(-)

--- a/drivers/net/xen-netback/netback.c
+++ b/drivers/net/xen-netback/netback.c
@@ -1016,6 +1016,8 @@ static int xenvif_tx_check_gop(struct xe
*/
struct skb_shared_info *first_shinfo = NULL;
int nr_frags = shinfo->nr_frags;
+ const bool sharedslot = nr_frags &&
+ frag_get_pending_idx(&shinfo->frags[0]) == pending_idx;
int i, err;

/* Check status of header. */
@@ -1028,7 +1030,10 @@ static int xenvif_tx_check_gop(struct xe
(*gopp_copy)->status,
pending_idx,
(*gopp_copy)->source.u.ref);
- xenvif_idx_release(vif, pending_idx, XEN_NETIF_RSP_ERROR);
+ /* The first frag might still have this slot mapped */
+ if (!sharedslot)
+ xenvif_idx_release(vif, pending_idx,
+ XEN_NETIF_RSP_ERROR);
}

check_frags:
@@ -1045,8 +1050,19 @@ check_frags:
pending_idx,
gop_map->handle);
/* Had a previous error? Invalidate this fragment. */
- if (unlikely(err))
+ if (unlikely(err)) {
xenvif_idx_unmap(vif, pending_idx);
+ /* If the mapping of the first frag was OK, but
+ * the header's copy failed, and they are
+ * sharing a slot, send an error
+ */
+ if (i == 0 && sharedslot)
+ xenvif_idx_release(vif, pending_idx,
+ XEN_NETIF_RSP_ERROR);
+ else
+ xenvif_idx_release(vif, pending_idx,
+ XEN_NETIF_RSP_OKAY);
+ }
continue;
}

@@ -1058,15 +1074,27 @@ check_frags:
gop_map->status,
pending_idx,
gop_map->ref);
+
xenvif_idx_release(vif, pending_idx, XEN_NETIF_RSP_ERROR);

/* Not the first error? Preceding frags already invalidated. */
if (err)
continue;
- /* First error: invalidate preceding fragments. */
+
+ /* First error: if the header haven't shared a slot with the
+ * first frag, release it as well.
+ */
+ if (!sharedslot)
+ xenvif_idx_release(vif,
+ XENVIF_TX_CB(skb)->pending_idx,
+ XEN_NETIF_RSP_OKAY);
+
+ /* Invalidate preceding fragments of this skb. */
for (j = 0; j < i; j++) {
pending_idx = frag_get_pending_idx(&shinfo->frags[j]);
xenvif_idx_unmap(vif, pending_idx);
+ xenvif_idx_release(vif, pending_idx,
+ XEN_NETIF_RSP_OKAY);
}

/* And if we found the error while checking the frag_list, unmap
@@ -1076,6 +1104,8 @@ check_frags:
for (j = 0; j < first_shinfo->nr_frags; j++) {
pending_idx = frag_get_pending_idx(&first_shinfo->frags[j]);
xenvif_idx_unmap(vif, pending_idx);
+ xenvif_idx_release(vif, pending_idx,
+ XEN_NETIF_RSP_OKAY);
}
}

@@ -1811,8 +1841,6 @@ void xenvif_idx_unmap(struct xenvif *vif
tx_unmap_op.status);
BUG();
}
-
- xenvif_idx_release(vif, pending_idx, XEN_NETIF_RSP_OKAY);
}

static inline int rx_work_todo(struct xenvif *vif)