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Date: Thu, 15 Apr 2010 22:30:32 +0200
From: Eric Dumazet <eric.dumazet@...il.com>
To: David Miller <davem@...emloft.net>
Cc: krkumar2@...ibm.com, netdev@...r.kernel.org,
nuclearcat@...learcat.com
Subject: Re: NULL pointer dereference panic in stable (2.6.33.2), amd64
Le jeudi 15 avril 2010 à 02:06 -0700, David Miller a écrit :
> From: Eric Dumazet <eric.dumazet@...il.com>
> Date: Thu, 15 Apr 2010 10:51:47 +0200
>
> > In any case, I think there is a fundamental problem with this sk
> > caching. Because one packet can travel in many stacked devices before
> > hitting the wire.
> >
> > (bonding, vlan, ethernet) for example.
> >
> > Socket cache is meaningfull for one level only...
>
> We were talking the other day about that 'tun' change to orphan the
> SKB on TX, and I mentioned the possibility of just doing this in some
> generic location before we give the packet to the device ->xmit()
> method.
>
> Such a scheme could help with this problem too.
Same thing we did with
if (dev->priv_flags & IFF_XMIT_DST_RELEASE)
skb_dst_drop(skb);
in dev_hard_start_xmit() ?
Problem is this skb_tstamp_tx() thing....
One possibility would be to change skb_orphan() to let everything done
by destructor.
One more argument would let destructor() know if this is the final
destructor() called from skb_release_head_state()
destructor() would be responsible to set skb->destructor and/or skb->sk
to NULL when possible.
All normal destructors would not care of this 2nd argument and just do
what they actually do, plus setting skb->sk = NULL, skb->destructor =
NULL
Fast path would stay as today, no extra test.
Only tstamp users would need to setup another destructor, a bit more
complex (it would have to take a look at 2nd argument before really
doing the job)
Completely untested patch to get the idea :
(to be completed for the tstamp thing)
include/linux/skbuff.h | 8 +++-----
include/net/sctp/sctp.h | 2 +-
include/net/sock.h | 4 ++--
net/caif/caif_socket.c | 4 +++-
net/core/dev.c | 26 +++++++++-----------------
net/core/skbuff.c | 2 +-
net/core/sock.c | 8 ++++++--
net/l2tp/l2tp_core.c | 4 +++-
net/netfilter/nf_tproxy_core.c | 2 +-
net/packet/af_packet.c | 4 ++--
net/unix/af_unix.c | 4 ++--
11 files changed, 33 insertions(+), 35 deletions(-)
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 38501d2..7dfd833 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -353,7 +353,7 @@ struct sk_buff {
kmemcheck_bitfield_end(flags1);
__be16 protocol;
- void (*destructor)(struct sk_buff *skb);
+ void (*destructor)(struct sk_buff *skb, int final);
#if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
struct nf_conntrack *nfct;
struct sk_buff *nfct_reasm;
@@ -1407,15 +1407,13 @@ static inline void pskb_trim_unique(struct sk_buff *skb, unsigned int len)
* @skb: buffer to orphan
*
* If a buffer currently has an owner then we call the owner's
- * destructor function and make the @skb unowned. The buffer continues
+ * destructor function. The buffer continues
* to exist but is no longer charged to its former owner.
*/
static inline void skb_orphan(struct sk_buff *skb)
{
if (skb->destructor)
- skb->destructor(skb);
- skb->destructor = NULL;
- skb->sk = NULL;
+ skb->destructor(skb, 0);
}
/**
diff --git a/include/net/sctp/sctp.h b/include/net/sctp/sctp.h
index 5915155..49e2162 100644
--- a/include/net/sctp/sctp.h
+++ b/include/net/sctp/sctp.h
@@ -130,7 +130,7 @@ int sctp_inet_listen(struct socket *sock, int backlog);
void sctp_write_space(struct sock *sk);
unsigned int sctp_poll(struct file *file, struct socket *sock,
poll_table *wait);
-void sctp_sock_rfree(struct sk_buff *skb);
+void sctp_sock_rfree(struct sk_buff *skb, int final);
void sctp_copy_sock(struct sock *newsk, struct sock *sk,
struct sctp_association *asoc);
extern struct percpu_counter sctp_sockets_allocated;
diff --git a/include/net/sock.h b/include/net/sock.h
index 56df440..a042c9d 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -988,8 +988,8 @@ extern struct sk_buff *sock_wmalloc(struct sock *sk,
extern struct sk_buff *sock_rmalloc(struct sock *sk,
unsigned long size, int force,
gfp_t priority);
-extern void sock_wfree(struct sk_buff *skb);
-extern void sock_rfree(struct sk_buff *skb);
+extern void sock_wfree(struct sk_buff *skb, int final);
+extern void sock_rfree(struct sk_buff *skb, int final);
extern int sock_setsockopt(struct socket *sock, int level,
int op, char __user *optval,
diff --git a/net/caif/caif_socket.c b/net/caif/caif_socket.c
index cdf62b9..4e7276a 100644
--- a/net/caif/caif_socket.c
+++ b/net/caif/caif_socket.c
@@ -256,10 +256,12 @@ static void caif_sktflowctrl_cb(struct cflayer *layr,
}
}
-static void skb_destructor(struct sk_buff *skb)
+static void skb_destructor(struct sk_buff *skb, int final)
{
dbfs_atomic_inc(&cnt.skb_free);
dbfs_atomic_dec(&cnt.skb_in_use);
+ skb->sk = NULL;
+ skb->destructor = NULL;
}
diff --git a/net/core/dev.c b/net/core/dev.c
index 876b111..9bffbe5 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -1828,12 +1828,12 @@ static int illegal_highdma(struct net_device *dev, struct sk_buff *skb)
}
struct dev_gso_cb {
- void (*destructor)(struct sk_buff *skb);
+ void (*destructor)(struct sk_buff *skb, int final);
};
#define DEV_GSO_CB(skb) ((struct dev_gso_cb *)(skb)->cb)
-static void dev_gso_skb_destructor(struct sk_buff *skb)
+static void dev_gso_skb_destructor(struct sk_buff *skb, int final)
{
struct dev_gso_cb *cb;
@@ -1847,7 +1847,9 @@ static void dev_gso_skb_destructor(struct sk_buff *skb)
cb = DEV_GSO_CB(skb);
if (cb->destructor)
- cb->destructor(skb);
+ cb->destructor(skb, final);
+ skb->sk = NULL;
+ skb->destructor = NULL;
}
/**
@@ -1904,23 +1906,11 @@ int dev_hard_start_xmit(struct sk_buff *skb, struct net_device *dev,
if (dev->priv_flags & IFF_XMIT_DST_RELEASE)
skb_dst_drop(skb);
+ skb_orphan(skb);
+
rc = ops->ndo_start_xmit(skb, dev);
if (rc == NETDEV_TX_OK)
txq_trans_update(txq);
- /*
- * TODO: if skb_orphan() was called by
- * dev->hard_start_xmit() (for example, the unmodified
- * igb driver does that; bnx2 doesn't), then
- * skb_tx_software_timestamp() will be unable to send
- * back the time stamp.
- *
- * How can this be prevented? Always create another
- * reference to the socket before calling
- * dev->hard_start_xmit()? Prevent that skb_orphan()
- * does anything in dev->hard_start_xmit() by clearing
- * the skb destructor before the call and restoring it
- * afterwards, then doing the skb_orphan() ourselves?
- */
return rc;
}
@@ -1938,6 +1928,8 @@ gso:
if (dev->priv_flags & IFF_XMIT_DST_RELEASE)
skb_dst_drop(nskb);
+ skb_orphan(nskb);
+
rc = ops->ndo_start_xmit(nskb, dev);
if (unlikely(rc != NETDEV_TX_OK)) {
if (rc & ~NETDEV_TX_MASK)
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index bdea0ef..90c171f 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -396,7 +396,7 @@ static void skb_release_head_state(struct sk_buff *skb)
#endif
if (skb->destructor) {
WARN_ON(in_irq());
- skb->destructor(skb);
+ skb->destructor(skb, 1);
}
#if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
nf_conntrack_put(skb->nfct);
diff --git a/net/core/sock.c b/net/core/sock.c
index 7effa1e..fcf67ea 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -1259,7 +1259,7 @@ void __init sk_init(void)
/*
* Write buffer destructor automatically called from kfree_skb.
*/
-void sock_wfree(struct sk_buff *skb)
+void sock_wfree(struct sk_buff *skb, int final)
{
struct sock *sk = skb->sk;
unsigned int len = skb->truesize;
@@ -1279,18 +1279,22 @@ void sock_wfree(struct sk_buff *skb)
*/
if (atomic_sub_and_test(len, &sk->sk_wmem_alloc))
__sk_free(sk);
+ skb->sk = NULL;
+ skb->destructor = NULL;
}
EXPORT_SYMBOL(sock_wfree);
/*
* Read buffer destructor automatically called from kfree_skb.
*/
-void sock_rfree(struct sk_buff *skb)
+void sock_rfree(struct sk_buff *skb, int final)
{
struct sock *sk = skb->sk;
atomic_sub(skb->truesize, &sk->sk_rmem_alloc);
sk_mem_uncharge(skb->sk, skb->truesize);
+ skb->sk = NULL;
+ skb->destructor = NULL;
}
EXPORT_SYMBOL(sock_rfree);
diff --git a/net/l2tp/l2tp_core.c b/net/l2tp/l2tp_core.c
index 98dfcce..a3b0a95 100644
--- a/net/l2tp/l2tp_core.c
+++ b/net/l2tp/l2tp_core.c
@@ -973,9 +973,11 @@ EXPORT_SYMBOL_GPL(l2tp_xmit_core);
/* Automatically called when the skb is freed.
*/
-static void l2tp_sock_wfree(struct sk_buff *skb)
+static void l2tp_sock_wfree(struct sk_buff *skb, int final)
{
sock_put(skb->sk);
+ skb->sk = NULL;
+ skb->destructor = NULL;
}
/* For data skbs that we transmit, we associate with the tunnel socket
diff --git a/net/netfilter/nf_tproxy_core.c b/net/netfilter/nf_tproxy_core.c
index 5490fc3..17dd2d9 100644
--- a/net/netfilter/nf_tproxy_core.c
+++ b/net/netfilter/nf_tproxy_core.c
@@ -55,7 +55,7 @@ nf_tproxy_get_sock_v4(struct net *net, const u8 protocol,
EXPORT_SYMBOL_GPL(nf_tproxy_get_sock_v4);
static void
-nf_tproxy_destructor(struct sk_buff *skb)
+nf_tproxy_destructor(struct sk_buff *skb, int final)
{
struct sock *sk = skb->sk;
diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index f162d59..dc8e843 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -808,7 +808,7 @@ ring_is_full:
goto drop_n_restore;
}
-static void tpacket_destruct_skb(struct sk_buff *skb)
+static void tpacket_destruct_skb(struct sk_buff *skb, int final)
{
struct packet_sock *po = pkt_sk(skb->sk);
void *ph;
@@ -823,7 +823,7 @@ static void tpacket_destruct_skb(struct sk_buff *skb)
__packet_set_status(po, ph, TP_STATUS_AVAILABLE);
}
- sock_wfree(skb);
+ sock_wfree(skb, final);
}
static int tpacket_fill_skb(struct packet_sock *po, struct sk_buff *skb,
diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index 3d9122e..17fca55 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -1303,7 +1303,7 @@ static void unix_detach_fds(struct scm_cookie *scm, struct sk_buff *skb)
unix_notinflight(scm->fp->fp[i]);
}
-static void unix_destruct_fds(struct sk_buff *skb)
+static void unix_destruct_fds(struct sk_buff *skb, int final)
{
struct scm_cookie scm;
memset(&scm, 0, sizeof(scm));
@@ -1312,7 +1312,7 @@ static void unix_destruct_fds(struct sk_buff *skb)
/* Alas, it calls VFS */
/* So fscking what? fput() had been SMP-safe since the last Summer */
scm_destroy(&scm);
- sock_wfree(skb);
+ sock_wfree(skb, final);
}
static int unix_attach_fds(struct scm_cookie *scm, struct sk_buff *skb)
--
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