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Subject[PATCH 5.2 11/66] net: neigh: fix multiple neigh timer scheduling
Date
From: Lorenzo Bianconi <lorenzo.bianconi@redhat.com>

[ Upstream commit 071c37983d99da07797294ea78e9da1a6e287144 ]

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>
Reviewed-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/core/neighbour.c | 2 ++
1 file changed, 2 insertions(+)

--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c
@@ -1122,6 +1122,7 @@ int __neigh_event_send(struct neighbour

atomic_set(&neigh->probes,
NEIGH_VAR(neigh->parms, UCAST_PROBES));
+ neigh_del_timer(neigh);
neigh->nud_state = NUD_INCOMPLETE;
neigh->updated = now;
next = now + max(NEIGH_VAR(neigh->parms, RETRANS_TIME),
@@ -1138,6 +1139,7 @@ int __neigh_event_send(struct neighbour
}
} else if (neigh->nud_state & NUD_STALE) {
neigh_dbg(2, "neigh %p is delayed\n", neigh);
+ neigh_del_timer(neigh);
neigh->nud_state = NUD_DELAY;
neigh->updated = jiffies;
neigh_add_timer(neigh, jiffies +

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