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 <ma...@cloudflare.com>
Fixes: 0c5c2d308906 ("neigh: Allow for user space users of the neighbour table")
Signed-off-by: Lorenzo Bianconi <lorenzo.bianc...@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
