[Devel] [PATCH RHEL7 COMMIT] ms/net, neigh: Fix null-ptr-deref in neigh_table_clear()

[Konstantin Khorenko]

The commit is pushed to "branch-rh7-3.10.0-1160.105.1.vz7.220.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh7-3.10.0-1160.105.1.vz7.220.1
------>
commit 1e7cebc6f9ec11f94ad58d4aaedcda99ff3dc8d3
Author: Chen Zhongjin <chenzhongjin at huawei.com>
Date:   Tue Jan 16 21:31:35 2024 +0200

    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)
    https://virtuozzo.atlassian.net/browse/PSBM-153018
    https://bugs.openvz.org/browse/OVZ-7410
    Signed-off-by: Alexander Atanasov <alexander.atanasov at virtuozzo.com>
    Reviewed-by: Pavel Tikhomirov <ptikhomirov at virtuozzo.com>
---
 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 e3b0f451943e..fafa43932f9e 100644
--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c
@@ -348,7 +348,7 @@ int neigh_ifdown(struct neigh_table *tbl, struct net_device *dev)
 	neigh_flush_dev(tbl, dev);
 	pneigh_ifdown(tbl, dev);
 	write_unlock_bh(&tbl->lock);
-	pneigh_queue_purge(&tbl->proxy_queue, dev_net(dev));
+	pneigh_queue_purge(&tbl->proxy_queue, dev ? dev_net(dev) : NULL);
 	if (skb_queue_empty(&tbl->proxy_queue))
 		del_timer_sync(&tbl->proxy_timer);
 	return 0;