[PATCH 3.15 075/109] xen-netback: Fix handling frag_list on grant op error path

Greg Kroah-Hartman
2014-07-26T19:02:37Z

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

[ Upstream commit 1a998d3e6bc1e44f4c0bc7509bdedef8ed3845ec ]

The error handling for skb's with frag_list was completely wrong, it caused
double unmap attempts to happen if the error was on the first skb. Move it to
the right place in the loop.

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 | 37 ++++++++++++++++++++-----------------
1 file changed, 20 insertions(+), 17 deletions(-)

--- a/drivers/net/xen-netback/netback.c
+++ b/drivers/net/xen-netback/netback.c
@@ -1007,10 +1007,16 @@ static int xenvif_tx_check_gop(struct xe
{
struct gnttab_map_grant_ref *gop_map = *gopp_map;
u16 pending_idx = XENVIF_TX_CB(skb)->pending_idx;
+ /* This always points to the shinfo of the skb being checked, which
+ * could be either the first or the one on the frag_list
+ */
struct skb_shared_info *shinfo = skb_shinfo(skb);
+ /* If this is non-NULL, we are currently checking the frag_list skb, and
+ * this points to the shinfo of the first one
+ */
+ struct skb_shared_info *first_shinfo = NULL;
int nr_frags = shinfo->nr_frags;
int i, err;
- struct sk_buff *first_skb = NULL;

/* Check status of header. */
err = (*gopp_copy)->status;
@@ -1063,31 +1069,28 @@ check_frags:
xenvif_idx_unmap(vif, pending_idx);
}

+ /* And if we found the error while checking the frag_list, unmap
+ * the first skb's frags
+ */
+ if (first_shinfo) {
+ 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);
+ }
+ }
+
/* Remember the error: invalidate all subsequent fragments. */
err = newerr;
}

- if (skb_has_frag_list(skb)) {
- first_skb = skb;
- skb = shinfo->frag_list;
- shinfo = skb_shinfo(skb);
+ if (skb_has_frag_list(skb) && !first_shinfo) {
+ first_shinfo = skb_shinfo(skb);
+ shinfo = skb_shinfo(skb_shinfo(skb)->frag_list);
nr_frags = shinfo->nr_frags;

goto check_frags;
}

- /* There was a mapping error in the frag_list skb. We have to unmap
- * the first skb's frags
- */
- if (first_skb && err) {
- int j;
- shinfo = skb_shinfo(first_skb);
- for (j = 0; j < shinfo->nr_frags; j++) {
- pending_idx = frag_get_pending_idx(&shinfo->frags[j]);
- xenvif_idx_unmap(vif, pending_idx);
- }
- }
-
*gopp_map = gop_map;
return err;
}