[Devel] [PATCH RHEL9 COMMIT] ms/net, neigh: Fix null-ptr-deref in neigh_table_clear()

[Konstantin Khorenko]

The commit is pushed to "branch-rh9-5.14.0-284.11.1.vz9.25.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh9-5.14.0-284.11.1.el9
------>
commit d47d786052c0003ac68eb59cd9c5e028c0cb73d7
Author: Chen Zhongjin <chenzhongjin at huawei.com>
Date:   Tue Nov 1 20:15:52 2022 +0800

    ms/net, neigh: Fix null-ptr-deref in neigh_table_clear()
    
    When IPv6 module gets initialized but hits an error in the middle,
    kenel panic with:
    
    KASAN: null-ptr-deref in range [0x0000000000000598-0x000000000000059f]
    CPU: 1 PID: 361 Comm: insmod
    Hardware name: QEMU Standard PC (i440FX + PIIX, 1996)
    RIP: 0010:__neigh_ifdown.isra.0+0x24b/0x370
    RSP: 0018:ffff888012677908 EFLAGS: 00000202
    ...
    Call Trace:
     <TASK>
     neigh_table_clear+0x94/0x2d0
     ndisc_cleanup+0x27/0x40 [ipv6]
     inet6_init+0x21c/0x2cb [ipv6]
     do_one_initcall+0xd3/0x4d0
     do_init_module+0x1ae/0x670
    ...
    Kernel panic - not syncing: Fatal exception
    
    When ipv6 initialization fails, it will try to cleanup and calls:
    
    neigh_table_clear()
      neigh_ifdown(tbl, NULL)
        pneigh_queue_purge(&tbl->proxy_queue, dev_net(dev == NULL))
        # dev_net(NULL) triggers null-ptr-deref.
    
    Fix it by passing NULL to pneigh_queue_purge() in neigh_ifdown() if dev
    is NULL, to make kernel not panic immediately.
    
    mFixes: 66ba215cb513 ("neigh: fix possible DoS due to net iface start/stop loop")
    Signed-off-by: Chen Zhongjin <chenzhongjin at huawei.com>
    Reviewed-by: Eric Dumazet <edumazet at google.com>
    Reviewed-by: Denis V. Lunev <den at openvz.org>
    Link: https://lore.kernel.org/r/20221101121552.21890-1-chenzhongjin@huawei.com
    Signed-off-by: Jakub Kicinski <kuba at kernel.org>
    
    (cherry picked from commit f8017317cb0b279b8ab98b0f3901a2e0ac880dad)
    Signed-off-by: Konstantin Khorenko <khorenko at virtuozzo.com>
    
    Feature: fix ms/net
---
 net/core/neighbour.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/core/neighbour.c b/net/core/neighbour.c
index e41708335ba2..75590a4787fc 100644
--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c
@@ -385,7 +385,7 @@ static int __neigh_ifdown(struct neigh_table *tbl, struct net_device *dev,
 	write_lock_bh(&tbl->lock);
 	neigh_flush_dev(tbl, dev, skip_perm);
 	pneigh_ifdown_and_unlock(tbl, dev);
-	pneigh_queue_purge(&tbl->proxy_queue, dev_net(dev));
+	pneigh_queue_purge(&tbl->proxy_queue, dev ? dev_net(dev) : NULL);
 	if (skb_queue_empty_lockless(&tbl->proxy_queue))
 		del_timer_sync(&tbl->proxy_timer);
 	return 0;