[PATCH 3.10 086/104] xen-netfront: fix resource leak in netfront

Greg Kroah-Hartman
2014-02-04T22:42:00Z

From: Annie Li <annie.li@oracle.com>

[ Upstream commit cefe0078eea52af17411eb1248946a94afb84ca5 ]

This patch removes grant transfer releasing code from netfront, and uses
gnttab_end_foreign_access to end grant access since
gnttab_end_foreign_access_ref may fail when the grant entry is
currently used for reading or writing.

* clean up grant transfer code kept from old netfront(2.6.18) which grants
pages for access/map and transfer. But grant transfer is deprecated in current
netfront, so remove corresponding release code for transfer.

* fix resource leak, release grant access (through gnttab_end_foreign_access)
and skb for tx/rx path, use get_page to ensure page is released when grant
access is completed successfully.

Xen-blkfront/xen-tpmfront/xen-pcifront also have similar issue, but patches
for them will be created separately.

V6: Correct subject line and commit message.

V5: Remove unecessary change in xennet_end_access.

V4: Revert put_page in gnttab_end_foreign_access, and keep netfront change in
single patch.

V3: Changes as suggestion from David Vrabel, ensure pages are not freed untill
grant acess is ended.

V2: Improve patch comments.

Signed-off-by: Annie Li <annie.li@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/net/xen-netfront.c | 88 +++++++++++++--------------------------------
1 file changed, 26 insertions(+), 62 deletions(-)

--- a/drivers/net/xen-netfront.c
+++ b/drivers/net/xen-netfront.c
@@ -107,6 +107,7 @@ struct netfront_info {
} tx_skbs[NET_TX_RING_SIZE];
grant_ref_t gref_tx_head;
grant_ref_t grant_tx_ref[NET_TX_RING_SIZE];
+ struct page *grant_tx_page[NET_TX_RING_SIZE];
unsigned tx_skb_freelist;

spinlock_t rx_lock ____cacheline_aligned_in_smp;
@@ -386,6 +387,7 @@ static void xennet_tx_buf_gc(struct net_
gnttab_release_grant_reference(
&np->gref_tx_head, np->grant_tx_ref[id]);
np->grant_tx_ref[id] = GRANT_INVALID_REF;
+ np->grant_tx_page[id] = NULL;
add_id_to_freelist(&np->tx_skb_freelist, np->tx_skbs, id);
dev_kfree_skb_irq(skb);
}
@@ -442,6 +444,7 @@ static void xennet_make_frags(struct sk_
gnttab_grant_foreign_access_ref(ref, np->xbdev->otherend_id,
mfn, GNTMAP_readonly);

+ np->grant_tx_page[id] = virt_to_page(data);
tx->gref = np->grant_tx_ref[id] = ref;
tx->offset = offset;
tx->size = len;
@@ -487,6 +490,7 @@ static void xennet_make_frags(struct sk_
np->xbdev->otherend_id,
mfn, GNTMAP_readonly);

+ np->grant_tx_page[id] = page;
tx->gref = np->grant_tx_ref[id] = ref;
tx->offset = offset;
tx->size = bytes;
@@ -586,6 +590,7 @@ static int xennet_start_xmit(struct sk_b
mfn = virt_to_mfn(data);
gnttab_grant_foreign_access_ref(
ref, np->xbdev->otherend_id, mfn, GNTMAP_readonly);
+ np->grant_tx_page[id] = virt_to_page(data);
tx->gref = np->grant_tx_ref[id] = ref;
tx->offset = offset;
tx->size = len;
@@ -1115,10 +1120,11 @@ static void xennet_release_tx_bufs(struc
continue;

skb = np->tx_skbs[i].skb;
- gnttab_end_foreign_access_ref(np->grant_tx_ref[i],
- GNTMAP_readonly);
- gnttab_release_grant_reference(&np->gref_tx_head,
- np->grant_tx_ref[i]);
+ get_page(np->grant_tx_page[i]);
+ gnttab_end_foreign_access(np->grant_tx_ref[i],
+ GNTMAP_readonly,
+ (unsigned long)page_address(np->grant_tx_page[i]));
+ np->grant_tx_page[i] = NULL;
np->grant_tx_ref[i] = GRANT_INVALID_REF;
add_id_to_freelist(&np->tx_skb_freelist, np->tx_skbs, i);
dev_kfree_skb_irq(skb);
@@ -1127,78 +1133,35 @@ static void xennet_release_tx_bufs(struc

static void xennet_release_rx_bufs(struct netfront_info *np)
{
- struct mmu_update *mmu = np->rx_mmu;
- struct multicall_entry *mcl = np->rx_mcl;
- struct sk_buff_head free_list;
- struct sk_buff *skb;
- unsigned long mfn;
- int xfer = 0, noxfer = 0, unused = 0;
int id, ref;

- dev_warn(&np->netdev->dev, "%s: fix me for copying receiver.\n",
- __func__);
- return;
-
- skb_queue_head_init(&free_list);
-
spin_lock_bh(&np->rx_lock);

for (id = 0; id < NET_RX_RING_SIZE; id++) {
- ref = np->grant_rx_ref[id];
- if (ref == GRANT_INVALID_REF) {
- unused++;
- continue;
- }
+ struct sk_buff *skb;
+ struct page *page;

skb = np->rx_skbs[id];
- mfn = gnttab_end_foreign_transfer_ref(ref);
- gnttab_release_grant_reference(&np->gref_rx_head, ref);
- np->grant_rx_ref[id] = GRANT_INVALID_REF;
-
- if (0 == mfn) {
- skb_shinfo(skb)->nr_frags = 0;
- dev_kfree_skb(skb);
- noxfer++;
+ if (!skb)
continue;
- }

- if (!xen_feature(XENFEAT_auto_translated_physmap)) {
- /* Remap the page. */
- const struct page *page =
- skb_frag_page(&skb_shinfo(skb)->frags[0]);
- unsigned long pfn = page_to_pfn(page);
- void *vaddr = page_address(page);
+ ref = np->grant_rx_ref[id];
+ if (ref == GRANT_INVALID_REF)
+ continue;

- MULTI_update_va_mapping(mcl, (unsigned long)vaddr,
- mfn_pte(mfn, PAGE_KERNEL),
- 0);
- mcl++;
- mmu->ptr = ((u64)mfn << PAGE_SHIFT)
- | MMU_MACHPHYS_UPDATE;
- mmu->val = pfn;
- mmu++;
+ page = skb_frag_page(&skb_shinfo(skb)->frags[0]);

- set_phys_to_machine(pfn, mfn);
- }
- __skb_queue_tail(&free_list, skb);
- xfer++;
- }
-
- dev_info(&np->netdev->dev, "%s: %d xfer, %d noxfer, %d unused\n",
- __func__, xfer, noxfer, unused);
+ /* gnttab_end_foreign_access() needs a page ref until
+ * foreign access is ended (which may be deferred).
+ */
+ get_page(page);
+ gnttab_end_foreign_access(ref, 0,
+ (unsigned long)page_address(page));
+ np->grant_rx_ref[id] = GRANT_INVALID_REF;

- if (xfer) {
- if (!xen_feature(XENFEAT_auto_translated_physmap)) {
- /* Do all the remapping work and M2P updates. */
- MULTI_mmu_update(mcl, np->rx_mmu, mmu - np->rx_mmu,
- NULL, DOMID_SELF);
- mcl++;
- HYPERVISOR_multicall(np->rx_mcl, mcl - np->rx_mcl);
- }
+ kfree_skb(skb);
}

- __skb_queue_purge(&free_list);
-
spin_unlock_bh(&np->rx_lock);
}

@@ -1333,6 +1296,7 @@ static struct net_device *xennet_create_
for (i = 0; i < NET_RX_RING_SIZE; i++) {
np->rx_skbs[i] = NULL;
np->grant_rx_ref[i] = GRANT_INVALID_REF;
+ np->grant_tx_page[i] = NULL;
}

/* A grant for every tx ring slot */