path: root/net
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authorDavid Woodhouse <dwmw2@infradead.org>2018-06-16 11:55:44 +0100
committerDavid S. Miller <davem@davemloft.net>2018-06-17 08:27:01 +0900
commit9bbe60a67be5a1c6f79b3c9be5003481a50529ff (patch)
treec02a003187d3c3a5b2b5db65d3bb9d0bf3bea85e /net
parent0841d98641bdb9c7f873adf7f6865ab0880ddfc7 (diff)
atm: Preserve value of skb->truesize when accounting to vcc
ATM accounts for in-flight TX packets in sk_wmem_alloc of the VCC on which they are to be sent. But it doesn't take ownership of those packets from the sock (if any) which originally owned them. They should remain owned by their actual sender until they've left the box. There's a hack in pskb_expand_head() to avoid adjusting skb->truesize for certain skbs, precisely to avoid messing up sk_wmem_alloc accounting. Ideally that hack would cover the ATM use case too, but it doesn't — skbs which aren't owned by any sock, for example PPP control frames, still get their truesize adjusted when the low-level ATM driver adds headroom. This has always been an issue, it seems. The truesize of a packet increases, and sk_wmem_alloc on the VCC goes negative. But this wasn't for normal traffic, only for control frames. So I think we just got away with it, and we probably needed to send 2GiB of LCP echo frames before the misaccounting would ever have caused a problem and caused atm_may_send() to start refusing packets. Commit 14afee4b609 ("net: convert sock.sk_wmem_alloc from atomic_t to refcount_t") did exactly what it was intended to do, and turned this mostly-theoretical problem into a real one, causing PPPoATM to fail immediately as sk_wmem_alloc underflows and atm_may_send() *immediately* starts refusing to allow new packets. The least intrusive solution to this problem is to stash the value of skb->truesize that was accounted to the VCC, in a new member of the ATM_SKB(skb) structure. Then in atm_pop_raw() subtract precisely that value instead of the then-current value of skb->truesize. Fixes: 158f323b9868 ("net: adjust skb->truesize in pskb_expand_head()") Signed-off-by: David Woodhouse <dwmw2@infradead.org> Tested-by: Kevin Darbyshire-Bryant <ldir@darbyshire-bryant.me.uk> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net')
7 files changed, 8 insertions, 14 deletions
diff --git a/net/atm/br2684.c b/net/atm/br2684.c
index 36b3adacc0dd..10462de734ea 100644
--- a/net/atm/br2684.c
+++ b/net/atm/br2684.c
@@ -252,8 +252,7 @@ static int br2684_xmit_vcc(struct sk_buff *skb, struct net_device *dev,
ATM_SKB(skb)->vcc = atmvcc = brvcc->atmvcc;
pr_debug("atm_skb(%p)->vcc(%p)->dev(%p)\n", skb, atmvcc, atmvcc->dev);
- refcount_add(skb->truesize, &sk_atm(atmvcc)->sk_wmem_alloc);
- ATM_SKB(skb)->atm_options = atmvcc->atm_options;
+ atm_account_tx(atmvcc, skb);
dev->stats.tx_bytes += skb->len;
diff --git a/net/atm/clip.c b/net/atm/clip.c
index 66caa48a27c2..d795b9c5aea4 100644
--- a/net/atm/clip.c
+++ b/net/atm/clip.c
@@ -381,8 +381,7 @@ static netdev_tx_t clip_start_xmit(struct sk_buff *skb,
memcpy(here, llc_oui, sizeof(llc_oui));
((__be16 *) here)[3] = skb->protocol;
- refcount_add(skb->truesize, &sk_atm(vcc)->sk_wmem_alloc);
- ATM_SKB(skb)->atm_options = vcc->atm_options;
+ atm_account_tx(vcc, skb);
entry->vccs->last_use = jiffies;
pr_debug("atm_skb(%p)->vcc(%p)->dev(%p)\n", skb, vcc, vcc->dev);
old = xchg(&entry->vccs->xoff, 1); /* assume XOFF ... */
diff --git a/net/atm/common.c b/net/atm/common.c
index 1f2af59935db..ff5748b2190f 100644
--- a/net/atm/common.c
+++ b/net/atm/common.c
@@ -630,10 +630,9 @@ int vcc_sendmsg(struct socket *sock, struct msghdr *m, size_t size)
goto out;
pr_debug("%d += %d\n", sk_wmem_alloc_get(sk), skb->truesize);
- refcount_add(skb->truesize, &sk->sk_wmem_alloc);
+ atm_account_tx(vcc, skb);
skb->dev = NULL; /* for paths shared with net_device interfaces */
- ATM_SKB(skb)->atm_options = vcc->atm_options;
if (!copy_from_iter_full(skb_put(skb, size), size, &m->msg_iter)) {
error = -EFAULT;
diff --git a/net/atm/lec.c b/net/atm/lec.c
index 5a95fcf6f9b6..d7f5cf5b7594 100644
--- a/net/atm/lec.c
+++ b/net/atm/lec.c
@@ -182,9 +182,8 @@ lec_send(struct atm_vcc *vcc, struct sk_buff *skb)
struct net_device *dev = skb->dev;
ATM_SKB(skb)->vcc = vcc;
- ATM_SKB(skb)->atm_options = vcc->atm_options;
+ atm_account_tx(vcc, skb);
- refcount_add(skb->truesize, &sk_atm(vcc)->sk_wmem_alloc);
if (vcc->send(vcc, skb) < 0) {
diff --git a/net/atm/mpc.c b/net/atm/mpc.c
index 75620c2f2617..24b53c4c39c6 100644
--- a/net/atm/mpc.c
+++ b/net/atm/mpc.c
@@ -555,8 +555,7 @@ static int send_via_shortcut(struct sk_buff *skb, struct mpoa_client *mpc)
sizeof(struct llc_snap_hdr));
- refcount_add(skb->truesize, &sk_atm(entry->shortcut)->sk_wmem_alloc);
- ATM_SKB(skb)->atm_options = entry->shortcut->atm_options;
+ atm_account_tx(entry->shortcut, skb);
entry->shortcut->send(entry->shortcut, skb);
diff --git a/net/atm/pppoatm.c b/net/atm/pppoatm.c
index 21d9d341a619..af8c4b38b746 100644
--- a/net/atm/pppoatm.c
+++ b/net/atm/pppoatm.c
@@ -350,8 +350,7 @@ static int pppoatm_send(struct ppp_channel *chan, struct sk_buff *skb)
return 1;
- refcount_add(skb->truesize, &sk_atm(ATM_SKB(skb)->vcc)->sk_wmem_alloc);
- ATM_SKB(skb)->atm_options = ATM_SKB(skb)->vcc->atm_options;
+ atm_account_tx(vcc, skb);
skb, ATM_SKB(skb)->vcc, ATM_SKB(skb)->vcc->dev);
ret = ATM_SKB(skb)->vcc->send(ATM_SKB(skb)->vcc, skb)
diff --git a/net/atm/raw.c b/net/atm/raw.c
index ee10e8d46185..b3ba44aab0ee 100644
--- a/net/atm/raw.c
+++ b/net/atm/raw.c
@@ -35,8 +35,8 @@ static void atm_pop_raw(struct atm_vcc *vcc, struct sk_buff *skb)
struct sock *sk = sk_atm(vcc);
pr_debug("(%d) %d -= %d\n",
- vcc->vci, sk_wmem_alloc_get(sk), skb->truesize);
- WARN_ON(refcount_sub_and_test(skb->truesize, &sk->sk_wmem_alloc));
+ vcc->vci, sk_wmem_alloc_get(sk), ATM_SKB(skb)->acct_truesize);
+ WARN_ON(refcount_sub_and_test(ATM_SKB(skb)->acct_truesize, &sk->sk_wmem_alloc));

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