diff options
| -rw-r--r-- | target/linux/generic/backport-4.14/080-net-convert-sock.sk_wmem_alloc-from-atomic_t-to-refc.patch | 172 |
1 files changed, 172 insertions, 0 deletions
diff --git a/target/linux/generic/backport-4.14/080-net-convert-sock.sk_wmem_alloc-from-atomic_t-to-refc.patch b/target/linux/generic/backport-4.14/080-net-convert-sock.sk_wmem_alloc-from-atomic_t-to-refc.patch new file mode 100644 index 0000000000..06d00886f1 --- /dev/null +++ b/target/linux/generic/backport-4.14/080-net-convert-sock.sk_wmem_alloc-from-atomic_t-to-refc.patch @@ -0,0 +1,172 @@ +From 9bbe60a67be5a1c6f79b3c9be5003481a50529ff Mon Sep 17 00:00:00 2001 +From: David Woodhouse <dwmw2@infradead.org> +Date: Sat, 16 Jun 2018 11:55:44 +0100 +Subject: atm: Preserve value of skb->truesize when accounting to vcc +MIME-Version: 1.0 +Content-Type: text/plain; charset=UTF-8 +Content-Transfer-Encoding: 8bit + +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> +--- + include/linux/atmdev.h | 15 +++++++++++++++ + net/atm/br2684.c | 3 +-- + net/atm/clip.c | 3 +-- + net/atm/common.c | 3 +-- + net/atm/lec.c | 3 +-- + net/atm/mpc.c | 3 +-- + net/atm/pppoatm.c | 3 +-- + net/atm/raw.c | 4 ++-- + 8 files changed, 23 insertions(+), 14 deletions(-) + +--- a/include/linux/atmdev.h ++++ b/include/linux/atmdev.h +@@ -214,6 +214,7 @@ struct atmphy_ops { + struct atm_skb_data { + struct atm_vcc *vcc; /* ATM VCC */ + unsigned long atm_options; /* ATM layer options */ ++ unsigned int acct_truesize; /* truesize accounted to vcc */ + }; + + #define VCC_HTABLE_SIZE 32 +@@ -241,6 +242,20 @@ void vcc_insert_socket(struct sock *sk); + + void atm_dev_release_vccs(struct atm_dev *dev); + ++static inline void atm_account_tx(struct atm_vcc *vcc, struct sk_buff *skb) ++{ ++ /* ++ * Because ATM skbs may not belong to a sock (and we don't ++ * necessarily want to), skb->truesize may be adjusted, ++ * escaping the hack in pskb_expand_head() which avoids ++ * doing so for some cases. So stash the value of truesize ++ * at the time we accounted it, and atm_pop_raw() can use ++ * that value later, in case it changes. ++ */ ++ refcount_add(skb->truesize, &sk_atm(vcc)->sk_wmem_alloc); ++ ATM_SKB(skb)->acct_truesize = skb->truesize; ++ ATM_SKB(skb)->atm_options = vcc->atm_options; ++} + + static inline void atm_force_charge(struct atm_vcc *vcc,int truesize) + { +--- a/net/atm/br2684.c ++++ b/net/atm/br2684.c +@@ -252,8 +252,7 @@ static int br2684_xmit_vcc(struct sk_buf + + 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_packets++; + dev->stats.tx_bytes += skb->len; + +--- a/net/atm/clip.c ++++ b/net/atm/clip.c +@@ -381,8 +381,7 @@ static netdev_tx_t clip_start_xmit(struc + 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 ... */ +--- a/net/atm/common.c ++++ b/net/atm/common.c +@@ -630,10 +630,9 @@ int vcc_sendmsg(struct socket *sock, str + 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)) { + kfree_skb(skb); + error = -EFAULT; +--- a/net/atm/lec.c ++++ b/net/atm/lec.c +@@ -182,9 +182,8 @@ lec_send(struct atm_vcc *vcc, struct sk_ + 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) { + dev->stats.tx_dropped++; + return; +--- a/net/atm/mpc.c ++++ b/net/atm/mpc.c +@@ -555,8 +555,7 @@ static int send_via_shortcut(struct sk_b + 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); + entry->packets_fwded++; + mpc->in_ops->put(entry); +--- a/net/atm/pppoatm.c ++++ b/net/atm/pppoatm.c +@@ -350,8 +350,7 @@ static int pppoatm_send(struct ppp_chann + 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); + pr_debug("atm_skb(%p)->vcc(%p)->dev(%p)\n", + skb, ATM_SKB(skb)->vcc, ATM_SKB(skb)->vcc->dev); + ret = ATM_SKB(skb)->vcc->send(ATM_SKB(skb)->vcc, skb) +--- a/net/atm/raw.c ++++ b/net/atm/raw.c +@@ -35,8 +35,8 @@ static void atm_pop_raw(struct atm_vcc * + 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)); + dev_kfree_skb_any(skb); + sk->sk_write_space(sk); + } |