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From: Lorenzo Bianconi <lorenzo.bianconi@redhat.com>
To: davem@davemloft.net
Cc: netdev@vger.kernel.org, dsahern@gmail.com, marek@cloudflare.com
Subject: [PATCH net v2] net: neigh: fix multiple neigh timer scheduling
Date: Sun, 14 Jul 2019 10:45:22 +0200
Message-ID: <793a1166667e00a3553577e1505bebd435e22c88.1563041150.git.lorenzo.bianconi@redhat.com> (raw)

Neigh timer can be scheduled multiple times from userspace adding
multiple neigh entries and forcing the neigh timer scheduling passing
NTF_USE in the netlink requests.
This will result in a refcount leak and in the following dump stack:

[   32.465295] NEIGH: BUG, double timer add, state is 8
[   32.465308] CPU: 0 PID: 416 Comm: double_timer_ad Not tainted 5.2.0+ #65
[   32.465311] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.12.0-2.fc30 04/01/2014
[   32.465313] Call Trace:
[   32.465318]  dump_stack+0x7c/0xc0
[   32.465323]  __neigh_event_send+0x20c/0x880
[   32.465326]  ? ___neigh_create+0x846/0xfb0
[   32.465329]  ? neigh_lookup+0x2a9/0x410
[   32.465332]  ? neightbl_fill_info.constprop.0+0x800/0x800
[   32.465334]  neigh_add+0x4f8/0x5e0
[   32.465337]  ? neigh_xmit+0x620/0x620
[   32.465341]  ? find_held_lock+0x85/0xa0
[   32.465345]  rtnetlink_rcv_msg+0x204/0x570
[   32.465348]  ? rtnl_dellink+0x450/0x450
[   32.465351]  ? mark_held_locks+0x90/0x90
[   32.465354]  ? match_held_lock+0x1b/0x230
[   32.465357]  netlink_rcv_skb+0xc4/0x1d0
[   32.465360]  ? rtnl_dellink+0x450/0x450
[   32.465363]  ? netlink_ack+0x420/0x420
[   32.465366]  ? netlink_deliver_tap+0x115/0x560
[   32.465369]  ? __alloc_skb+0xc9/0x2f0
[   32.465372]  netlink_unicast+0x270/0x330
[   32.465375]  ? netlink_attachskb+0x2f0/0x2f0
[   32.465378]  netlink_sendmsg+0x34f/0x5a0
[   32.465381]  ? netlink_unicast+0x330/0x330
[   32.465385]  ? move_addr_to_kernel.part.0+0x20/0x20
[   32.465388]  ? netlink_unicast+0x330/0x330
[   32.465391]  sock_sendmsg+0x91/0xa0
[   32.465394]  ___sys_sendmsg+0x407/0x480
[   32.465397]  ? copy_msghdr_from_user+0x200/0x200
[   32.465401]  ? _raw_spin_unlock_irqrestore+0x37/0x40
[   32.465404]  ? lockdep_hardirqs_on+0x17d/0x250
[   32.465407]  ? __wake_up_common_lock+0xcb/0x110
[   32.465410]  ? __wake_up_common+0x230/0x230
[   32.465413]  ? netlink_bind+0x3e1/0x490
[   32.465416]  ? netlink_setsockopt+0x540/0x540
[   32.465420]  ? __fget_light+0x9c/0xf0
[   32.465423]  ? sockfd_lookup_light+0x8c/0xb0
[   32.465426]  __sys_sendmsg+0xa5/0x110
[   32.465429]  ? __ia32_sys_shutdown+0x30/0x30
[   32.465432]  ? __fd_install+0xe1/0x2c0
[   32.465435]  ? lockdep_hardirqs_off+0xb5/0x100
[   32.465438]  ? mark_held_locks+0x24/0x90
[   32.465441]  ? do_syscall_64+0xf/0x270
[   32.465444]  do_syscall_64+0x63/0x270
[   32.465448]  entry_SYSCALL_64_after_hwframe+0x49/0xbe

Fix the issue unscheduling neigh_timer if selected entry is in 'IN_TIMER'
receiving a netlink request with NTF_USE flag set

Reported-by: Marek Majkowski <marek@cloudflare.com>
Fixes: 0c5c2d308906 ("neigh: Allow for user space users of the neighbour table")
Signed-off-by: Lorenzo Bianconi <lorenzo.bianconi@redhat.com>
---
Changes since v1:
- fix compilation errors defining neigh_event_send_check_timer routine
---
 include/net/neighbour.h | 15 ++++++++++++---
 net/core/neighbour.c    | 11 ++++++++---
 2 files changed, 20 insertions(+), 6 deletions(-)

diff --git a/include/net/neighbour.h b/include/net/neighbour.h
index 50a67bd6a434..58bb515cea5d 100644
--- a/include/net/neighbour.h
+++ b/include/net/neighbour.h
@@ -324,7 +324,8 @@ static inline struct neighbour *neigh_create(struct neigh_table *tbl,
 	return __neigh_create(tbl, pkey, dev, true);
 }
 void neigh_destroy(struct neighbour *neigh);
-int __neigh_event_send(struct neighbour *neigh, struct sk_buff *skb);
+int __neigh_event_send(struct neighbour *neigh, struct sk_buff *skb,
+		       bool check_timer);
 int neigh_update(struct neighbour *neigh, const u8 *lladdr, u8 new, u32 flags,
 		 u32 nlmsg_pid);
 void __neigh_set_probe_once(struct neighbour *neigh);
@@ -435,17 +436,25 @@ static inline struct neighbour * neigh_clone(struct neighbour *neigh)
 
 #define neigh_hold(n)	refcount_inc(&(n)->refcnt)
 
-static inline int neigh_event_send(struct neighbour *neigh, struct sk_buff *skb)
+static inline int neigh_event_send_check_timer(struct neighbour *neigh,
+					       struct sk_buff *skb,
+					       bool check_timer)
 {
 	unsigned long now = jiffies;
 	
 	if (neigh->used != now)
 		neigh->used = now;
 	if (!(neigh->nud_state&(NUD_CONNECTED|NUD_DELAY|NUD_PROBE)))
-		return __neigh_event_send(neigh, skb);
+		return __neigh_event_send(neigh, skb, check_timer);
 	return 0;
 }
 
+static inline int neigh_event_send(struct neighbour *neigh,
+				   struct sk_buff *skb)
+{
+	return neigh_event_send_check_timer(neigh, skb, false);
+}
+
 #if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
 static inline int neigh_hh_bridge(struct hh_cache *hh, struct sk_buff *skb)
 {
diff --git a/net/core/neighbour.c b/net/core/neighbour.c
index 742cea4ce72e..0b63df6146f7 100644
--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c
@@ -1104,7 +1104,8 @@ static void neigh_timer_handler(struct timer_list *t)
 	neigh_release(neigh);
 }
 
-int __neigh_event_send(struct neighbour *neigh, struct sk_buff *skb)
+int __neigh_event_send(struct neighbour *neigh, struct sk_buff *skb,
+		       bool check_timer)
 {
 	int rc;
 	bool immediate_probe = false;
@@ -1124,7 +1125,9 @@ int __neigh_event_send(struct neighbour *neigh, struct sk_buff *skb)
 
 			atomic_set(&neigh->probes,
 				   NEIGH_VAR(neigh->parms, UCAST_PROBES));
-			neigh->nud_state     = NUD_INCOMPLETE;
+			if (check_timer)
+				neigh_del_timer(neigh);
+			neigh->nud_state = NUD_INCOMPLETE;
 			neigh->updated = now;
 			next = now + max(NEIGH_VAR(neigh->parms, RETRANS_TIME),
 					 HZ/2);
@@ -1140,6 +1143,8 @@ int __neigh_event_send(struct neighbour *neigh, struct sk_buff *skb)
 		}
 	} else if (neigh->nud_state & NUD_STALE) {
 		neigh_dbg(2, "neigh %p is delayed\n", neigh);
+		if (check_timer)
+			neigh_del_timer(neigh);
 		neigh->nud_state = NUD_DELAY;
 		neigh->updated = jiffies;
 		neigh_add_timer(neigh, jiffies +
@@ -1962,7 +1967,7 @@ static int neigh_add(struct sk_buff *skb, struct nlmsghdr *nlh,
 		flags |= NEIGH_UPDATE_F_ISROUTER;
 
 	if (ndm->ndm_flags & NTF_USE) {
-		neigh_event_send(neigh, NULL);
+		neigh_event_send_check_timer(neigh, NULL, true);
 		err = 0;
 	} else
 		err = __neigh_update(neigh, lladdr, ndm->ndm_state, flags,
-- 
2.21.0


             reply index

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-07-14  8:45 Lorenzo Bianconi [this message]
2019-07-14 13:58 ` David Ahern
2019-07-14 19:15   ` David Miller
2019-07-14 20:04   ` Lorenzo Bianconi

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