Re: RCU'ed dst_get_neighbour()

Eric Dumazet
2011-11-29T20:43:57Z

Le mardi 29 novembre 2011 à 19:01 +0100, Eric Dumazet a écrit :
> Le mardi 29 novembre 2011 à 10:44 -0700, Marc Aurele La France a écrit :
> > Hi.
> >
> > Commit (1) seems to imply that all dst_get_neighbour() references now need
> > to be wrapped with rcu_read_lock()/rcu_read_unlock() sequences. See (2)
> > for one such proposed change.
> >
> > In the case I have here (ipoib), this commit results in ...
> >
> > ===================================================
> > [ INFO: suspicious rcu_dereference_check() usage. ]
> > ---------------------------------------------------
> > include/net/dst.h:91 invoked rcu_dereference_check() without protection!
> >
> > other info that might help us debug this:
> >
> >
> > rcu_scheduler_active = 1, debug_locks = 1
> > 4 locks held by kworker/3:1/630:
> > #0: (ib_cm){.+.+.+}, at: [<ffffffff81055735>]
> > process_one_work+0x1ab/0x4f9
> > #1: ((&(&work->work)->work)){+.+.+.}, at: [<ffffffff81055735>]
> > process_one_work+0x1ab/0x4f9
> > #2: (rcu_read_lock_bh){.+....}, at: [<ffffffff81388216>]
> > dev_queue_xmit+0x0/0x5ae
> > #3: (_xmit_INFINIBAND){+.-...}, at: [<ffffffff8139eecc>]
> > sch_direct_xmit+0x4d/0x22b
> >
> > stack backtrace:
> > Pid: 630, comm: kworker/3:1 Not tainted 3.1.3-smp #1
> > Call Trace:
> > [<ffffffff8106c385>] lockdep_rcu_dereference+0x9b/0xa4
> > [<ffffffff81351cda>] ipoib_start_xmit+0xf4/0x36f
> > [<ffffffff81384215>] dev_hard_start_xmit+0x2a7/0x54f
> > [<ffffffff8139eeef>] sch_direct_xmit+0x70/0x22b
> > [<ffffffff8138851f>] dev_queue_xmit+0x309/0x5ae
> > [<ffffffff81388216>] ? napi_gro_receive+0xb3/0xb3
> > [<ffffffff813582d3>] ipoib_cm_rep_handler+0x208/0x248
> > [<ffffffff81433e16>] ? _raw_spin_unlock_irqrestore+0x3d/0x5b
> > [<ffffffff8135a912>] ipoib_cm_tx_handler+0x95/0x27f
> > [<ffffffff8106d183>] ? __trace_hardirqs_on_caller+0x41/0x65
> > [<ffffffff81327b29>] cm_process_work+0x26/0xbc
> > [<ffffffff81328d74>] cm_rep_handler+0x274/0x2ae
> > [<ffffffff81329582>] cm_work_handler+0x41/0x91
> > [<ffffffff8105582c>] process_one_work+0x2a2/0x4f9
> > [<ffffffff81055735>] ? process_one_work+0x1ab/0x4f9
> > [<ffffffff810580c6>] ? worker_thread+0x4a/0x1ca
> > [<ffffffff81329541>] ? cm_req_handler+0x355/0x355
> > [<ffffffff81058175>] worker_thread+0xf9/0x1ca
> > [<ffffffff8105807c>] ? gcwq_mayday_timeout+0x77/0x77
> > [<ffffffff8105bfa3>] kthread+0x86/0x8e
> > [<ffffffff81436b34>] kernel_thread_helper+0x4/0x10
> > [<ffffffff8143425d>] ? retint_restore_args+0xe/0xe
> > [<ffffffff8105bf1d>] ? kthread_stop+0x1cd/0x1cd
> > [<ffffffff81436b30>] ? gs_change+0xb/0xb
> >
> > ===================================================
> > [ INFO: suspicious rcu_dereference_check() usage. ]
> > ---------------------------------------------------
> > include/net/dst.h:91 invoked rcu_dereference_check() without protection!
> >
> > other info that might help us debug this:
> >
> >
> > rcu_scheduler_active = 1, debug_locks = 1
> > 2 locks held by kworker/u:2/748:
> > #0: ((name)){.+.+.+}, at: [<ffffffff81055735>]
> > process_one_work+0x1ab/0x4f9
> > #1: ((&port_priv->work)){+.+.+.}, at: [<ffffffff81055735>]
> > process_one_work+0x1ab/0x4f9
> >
> > stack backtrace:
> > Pid: 748, comm: kworker/u:2 Not tainted 3.1.3-smp #1
> > Call Trace:
> > [<ffffffff8106c385>] lockdep_rcu_dereference+0x9b/0xa4
> > [<ffffffff81354e68>] ipoib_mcast_join_finish+0x362/0x48a
> > [<ffffffff81355481>] ipoib_mcast_sendonly_join_complete+0x3b/0x174
> > [<ffffffff813246b3>] mcast_work_handler+0xba/0x182
> > [<ffffffff813248aa>] join_handler+0xe6/0xee
> > [<ffffffff81322af1>] ib_sa_mcmember_rec_callback+0x51/0x5c
> > [<ffffffff8132289c>] recv_handler+0x44/0x50
> > [<ffffffff8131efca>] ib_mad_complete_recv+0xc3/0x125
> > [<ffffffff8131debe>] ? find_mad_agent+0x13a/0x149
> > [<ffffffff8131f30a>] ib_mad_recv_done_handler+0x2de/0x326
> > [<ffffffff8131f3b0>] ib_mad_completion_handler+0x5e/0x91
> > [<ffffffff8105582c>] process_one_work+0x2a2/0x4f9
> > [<ffffffff81055735>] ? process_one_work+0x1ab/0x4f9
> > [<ffffffff810580c6>] ? worker_thread+0x4a/0x1ca
> > [<ffffffff8131f352>] ? ib_mad_recv_done_handler+0x326/0x326
> > [<ffffffff81058175>] worker_thread+0xf9/0x1ca
> > [<ffffffff8105807c>] ? gcwq_mayday_timeout+0x77/0x77
> > [<ffffffff8105bfa3>] kthread+0x86/0x8e
> > [<ffffffff81436b34>] kernel_thread_helper+0x4/0x10
> > [<ffffffff8143425d>] ? retint_restore_args+0xe/0xe
> > [<ffffffff8105bf1d>] ? kthread_stop+0x1cd/0x1cd
> > [<ffffffff81436b30>] ? gs_change+0xb/0xb
> >
> > Comments/flames?
> >
> > Thanks.
> >
> > Marc.
> >
> > PS: Please reply-to-all as I am not subscribed to netdev.
> >
> > (1) http://git.kernel.org/?p=linux/kernel/git/torvalds/linux.git;a=commitdiff;h=f2c31e32b378a6653f8de606149d963baf11d7d3
> > (2) http://www.spinics.net/lists/netdev/msg179639.html
> >
> > +----------------------------------+----------------------------------+
> > | Marc Aurele La France | work: 1-780-492-9310 |
> > | Academic Information and | fax: 1-780-492-1729 |
> > | Communications Technologies | email: tsi-yfeSBMgouQgsA/PxXw9srA@public.gmane.org |
> > | 352 General Services Building +----------------------------------+
> > | University of Alberta | |
> > | Edmonton, Alberta | Standard disclaimers apply |
> > | T6G 2H1 | |
> > | CANADA | |
> > +----------------------------------+----------------------------------+
>
> Thanks for the report Marc, I'll take a look asap.
>
>

Hi Marc

Here is the patch I cooked based on your report, thanks a lot !

Eric

[PATCH] net: infiniband/ulp/ipoib: fix lockdep splats

commit f2c31e32b37 (net: fix NULL dereferences in check_peer_redir())
forgot to take care of infiniband uses of dst neighbours.

Many thanks to Marc Aurele who provided a nice bug report.

Reported-by: Marc Aurele La France <tsi-yfeSBMgouQgsA/PxXw9srA@public.gmane.org>
Signed-off-by: Eric Dumazet <eric.dumazet-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
CC: David Miller <davem-fT/PcQaiUtIeIZ0/mPfg9Q@public.gmane.org>
CC: Roland Dreier <roland-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
---
drivers/infiniband/ulp/ipoib/ipoib_main.c | 17 ++++++++-------
drivers/infiniband/ulp/ipoib/ipoib_multicast.c | 6 +++--
2 files changed, 14 insertions(+), 9 deletions(-)

diff --git a/drivers/infiniband/ulp/ipoib/ipoib_main.c b/drivers/infiniband/ulp/ipoib/ipoib_main.c
index 7567b60..c36a2ab 100644
--- a/drivers/infiniband/ulp/ipoib/ipoib_main.c
+++ b/drivers/infiniband/ulp/ipoib/ipoib_main.c
@@ -555,6 +555,7 @@ static int path_rec_start(struct net_device *dev,
return 0;
}

+/* called with rcu_read_lock */
static void neigh_add_path(struct sk_buff *skb, struct net_device *dev)
{
struct ipoib_dev_priv *priv = netdev_priv(dev);
@@ -636,6 +637,7 @@ err_drop:
spin_unlock_irqrestore(&priv->lock, flags);
}

+/* called with rcu_read_lock */
static void ipoib_path_lookup(struct sk_buff *skb, struct net_device *dev)
{
struct ipoib_dev_priv *priv = netdev_priv(skb->dev);
@@ -720,13 +722,14 @@ static int ipoib_start_xmit(struct sk_buff *skb, struct net_device *dev)
struct neighbour *n = NULL;
unsigned long flags;

+ rcu_read_lock();
if (likely(skb_dst(skb)))
n = dst_get_neighbour(skb_dst(skb));

if (likely(n)) {
if (unlikely(!*to_ipoib_neigh(n))) {
ipoib_path_lookup(skb, dev);
- return NETDEV_TX_OK;
+ goto unlock;
}

neigh = *to_ipoib_neigh(n);
@@ -749,17 +752,17 @@ static int ipoib_start_xmit(struct sk_buff *skb, struct net_device *dev)
ipoib_neigh_free(dev, neigh);
spin_unlock_irqrestore(&priv->lock, flags);
ipoib_path_lookup(skb, dev);
- return NETDEV_TX_OK;
+ goto unlock;
}

if (ipoib_cm_get(neigh)) {
if (ipoib_cm_up(neigh)) {
ipoib_cm_send(dev, skb, ipoib_cm_get(neigh));
- return NETDEV_TX_OK;
+ goto unlock;
}
} else if (neigh->ah) {
ipoib_send(dev, skb, neigh->ah, IPOIB_QPN(n->ha));
- return NETDEV_TX_OK;
+ goto unlock;
}

if (skb_queue_len(&neigh->queue) < IPOIB_MAX_PATH_REC_QUEUE) {
@@ -793,13 +796,13 @@ static int ipoib_start_xmit(struct sk_buff *skb, struct net_device *dev)
phdr->hwaddr + 4);
dev_kfree_skb_any(skb);
++dev->stats.tx_dropped;
- return NETDEV_TX_OK;
+ goto unlock;
}

unicast_arp_send(skb, dev, phdr);
}
}
-
+unlock:
return NETDEV_TX_OK;
}

@@ -837,7 +840,7 @@ static int ipoib_hard_header(struct sk_buff *skb,
dst = skb_dst(skb);
n = NULL;
if (dst)
- n = dst_get_neighbour(dst);
+ n = dst_get_neighbour_raw(dst);
if ((!dst || !n) && daddr) {
struct ipoib_pseudoheader *phdr =
(struct ipoib_pseudoheader *) skb_push(skb, sizeof *phdr);
diff --git a/drivers/infiniband/ulp/ipoib/ipoib_multicast.c b/drivers/infiniband/ulp/ipoib/ipoib_multicast.c
index 1b7a976..cad1894 100644
--- a/drivers/infiniband/ulp/ipoib/ipoib_multicast.c
+++ b/drivers/infiniband/ulp/ipoib/ipoib_multicast.c
@@ -266,7 +266,7 @@ static int ipoib_mcast_join_finish(struct ipoib_mcast *mcast,

skb->dev = dev;
if (dst)
- n = dst_get_neighbour(dst);
+ n = dst_get_neighbour_raw(dst);
if (!dst || !n) {
/* put pseudoheader back on for next time */
skb_push(skb, sizeof (struct ipoib_pseudoheader));
@@ -722,6 +722,8 @@ out:
if (mcast && mcast->ah) {
struct dst_entry *dst = skb_dst(skb);
struct neighbour *n = NULL;
+
+ rcu_read_lock();
if (dst)
n = dst_get_neighbour(dst);
if (n && !*to_ipoib_neigh(n)) {
@@ -734,7 +736,7 @@ out:
list_add_tail(&neigh->list, &mcast->neigh_list);
}
}
-
+ rcu_read_unlock();
spin_unlock_irqrestore(&priv->lock, flags);
ipoib_send(dev, skb, mcast->ah, IB_MULTICAST_QPN);
return;