[PATCH net] net, neigh: Fix null-ptr-deref in neigh_table_clear()

[PATCH net] net, neigh: Fix null-ptr-deref in neigh_table_clear()

[Chen Zhongjin]

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.

Fixes: 66ba215cb513 ("neigh: fix possible DoS due to net iface start/stop loop")
Signed-off-by: Chen Zhongjin <chenzhongjin@huawei.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 3c4786b99907..a77a85e357e0 100644
--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c
@@ -409,7 +409,7 @@ 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;
-- 
2.17.1

Re: [PATCH net] net, neigh: Fix null-ptr-deref in neigh_table_clear()

[Eric Dumazet]

On Tue, Nov 1, 2022 at 5:19 AM Chen Zhongjin <chenzhongjin@huawei.com> wrote:
>
> 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.
>
> Fixes: 66ba215cb513 ("neigh: fix possible DoS due to net iface start/stop loop")
> Signed-off-by: Chen Zhongjin <chenzhongjin@huawei.com>
> ---

SGTM, thanks !

Reviewed-by: Eric Dumazet <edumazet@google.com>

Re: [PATCH net] net, neigh: Fix null-ptr-deref in neigh_table_clear()

[Denis V. Lunev]

On 11/1/22 13:15, Chen Zhongjin wrote:
> 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.
>
> Fixes: 66ba215cb513 ("neigh: fix possible DoS due to net iface start/stop loop")
> Signed-off-by: Chen Zhongjin <chenzhongjin@huawei.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 3c4786b99907..a77a85e357e0 100644
> --- a/net/core/neighbour.c
> +++ b/net/core/neighbour.c
> @@ -409,7 +409,7 @@ 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;
Reviewed-by: Denis V. Lunev <den@openvz.org>

Re: [PATCH net] net, neigh: Fix null-ptr-deref in neigh_table_clear()

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net.git (master)
by Jakub Kicinski <kuba@kernel.org>:

On Tue, 1 Nov 2022 20:15:52 +0800 you wrote:
> 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
> 
> [...]

Here is the summary with links:
  - [net] net, neigh: Fix null-ptr-deref in neigh_table_clear()
    https://git.kernel.org/netdev/net/c/f8017317cb0b

You are awesome, thank you!
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