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fix #1737: merge: net: fix deadlock while clearing neighbor proxy table

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Link: https://bugzilla.kernel.org/show_bug.cgi?id=199289
Signed-off-by: Wolfgang Bumiller <w.bumiller@proxmox.com>
This commit is contained in:
Wolfgang Bumiller 2018-04-25 08:23:41 +02:00 committed by Thomas Lamprecht
parent 62948cb62e
commit c9e0edd481
1 changed files with 95 additions and 0 deletions
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95
patches/kernel/0025-net-fix-deadlock-while-clearing-neighbor-proxy-table.patch Normal file
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@ -0,0 +1,95 @@
From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Wolfgang Bumiller <w.bumiller@proxmox.com>
Date: Mon, 9 Apr 2018 14:56:29 +0200
Subject: [PATCH linux] net: fix deadlock while clearing neighbor proxy table
When coming from ndisc_netdev_event() in net/ipv6/ndisc.c,
neigh_ifdown() is called with &nd_tbl, locking this while
clearing the proxy neighbor entries when eg. deleting an
interface. Calling the table's pndisc_destructor() with the
lock still held, however, can cause a deadlock: When a
multicast listener is available an IGMP packet of type
ICMPV6_MGM_REDUCTION may be sent out. When reaching
ip6_finish_output2(), if no neighbor entry for the target
address is found, __neigh_create() is called with &nd_tbl,
which it'll want to lock.
Move the elements into their own list, then unlock the table
and perform the destruction.
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=199289
Fixes: 6fd6ce2056de ("ipv6: Do not depend on rt->n in ip6_finish_output2().")
Signed-off-by: Wolfgang Bumiller <w.bumiller@proxmox.com>
---
net/core/neighbour.c | 28 ++++++++++++++++++----------
1 file changed, 18 insertions(+), 10 deletions(-)
diff --git a/net/core/neighbour.c b/net/core/neighbour.c
index 7b7a14abba28..e22d2aefbd78 100644
--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c
@@ -55,7 +55,8 @@ static void neigh_timer_handler(struct timer_list *t);
static void __neigh_notify(struct neighbour *n, int type, int flags,
u32 pid);
static void neigh_update_notify(struct neighbour *neigh, u32 nlmsg_pid);
-static int pneigh_ifdown(struct neigh_table *tbl, struct net_device *dev);
+static int pneigh_ifdown_and_unlock(struct neigh_table *tbl,
+ struct net_device *dev);
#ifdef CONFIG_PROC_FS
static const struct file_operations neigh_stat_seq_fops;
@@ -291,8 +292,7 @@ int neigh_ifdown(struct neigh_table *tbl, struct net_device *dev)
{
write_lock_bh(&tbl->lock);
neigh_flush_dev(tbl, dev);
- pneigh_ifdown(tbl, dev);
- write_unlock_bh(&tbl->lock);
+ pneigh_ifdown_and_unlock(tbl, dev);
del_timer_sync(&tbl->proxy_timer);
pneigh_queue_purge(&tbl->proxy_queue);
@@ -681,9 +681,10 @@ int pneigh_delete(struct neigh_table *tbl, struct net *net, const void *pkey,
return -ENOENT;
}
-static int pneigh_ifdown(struct neigh_table *tbl, struct net_device *dev)
+static int pneigh_ifdown_and_unlock(struct neigh_table *tbl,
+ struct net_device *dev)
{
- struct pneigh_entry *n, **np;
+ struct pneigh_entry *n, **np, *freelist = NULL;
u32 h;
for (h = 0; h <= PNEIGH_HASHMASK; h++) {
@@ -691,16 +692,23 @@ static int pneigh_ifdown(struct neigh_table *tbl, struct net_device *dev)
while ((n = *np) != NULL) {
if (!dev || n->dev == dev) {
*np = n->next;
- if (tbl->pdestructor)
- tbl->pdestructor(n);
- if (n->dev)
- dev_put(n->dev);
- kfree(n);
+ n->next = freelist;
+ freelist = n;
continue;
}
np = &n->next;
}
}
+ write_unlock_bh(&tbl->lock);
+ while ((n = freelist)) {
+ freelist = n->next;
+ n->next = NULL;
+ if (tbl->pdestructor)
+ tbl->pdestructor(n);
+ if (n->dev)
+ dev_put(n->dev);
+ kfree(n);
+ }
return -ENOENT;
}
--
2.11.0