[PATCH nf] netfilter: nf_tables: fix possible oops when dumping stateful objects

[PATCH nf] netfilter: nf_tables: fix possible oops when dumping stateful objects

[Liping Zhang]

From: Liping Zhang <zlpnobody@gmail.com>

When dumping nft stateful objects, if NFTA_OBJ_TABLE and NFTA_OBJ_TYPE
attributes are not specified either, filter will become NULL, so oops
will happen(actually nft utility will always set NFTA_OBJ_TABLE attr,
so I write a test program to make this happen):

  BUG: unable to handle kernel NULL pointer dereference at (null)
  IP: nf_tables_dump_obj+0x17c/0x330 [nf_tables]
  [...]
  Call Trace:
  ? nf_tables_dump_obj+0x5/0x330 [nf_tables]
  ? __kmalloc_reserve.isra.35+0x31/0x90
  ? __alloc_skb+0x5b/0x1e0
  netlink_dump+0x124/0x2a0
  __netlink_dump_start+0x161/0x190
  nf_tables_getobj+0xe8/0x280 [nf_tables]

Fixes: a9fea2a3c3cf ("netfilter: nf_tables: allow to filter stateful object dumps by type")
Signed-off-by: Liping Zhang <zlpnobody@gmail.com>
---
 net/netfilter/nf_tables_api.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index 0db5f97..091d2dc 100644
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -4262,10 +4262,11 @@ static int nf_tables_dump_obj(struct sk_buff *skb, struct netlink_callback *cb)
 				if (idx > s_idx)
 					memset(&cb->args[1], 0,
 					       sizeof(cb->args) - sizeof(cb->args[0]));
-				if (filter->table[0] &&
+				if (filter && filter->table[0] &&
 				    strcmp(filter->table, table->name))
 					goto cont;
-				if (filter->type != NFT_OBJECT_UNSPEC &&
+				if (filter &&
+				    filter->type != NFT_OBJECT_UNSPEC &&
 				    obj->type->type != filter->type)
 					goto cont;
 
-- 
2.5.5

Re: [PATCH nf] netfilter: nf_tables: fix possible oops when dumping stateful objects

[Pablo Neira Ayuso]

On Sat, Jan 07, 2017 at 08:51:50PM +0800, Liping Zhang wrote:
> From: Liping Zhang <zlpnobody@gmail.com>
> 
> When dumping nft stateful objects, if NFTA_OBJ_TABLE and NFTA_OBJ_TYPE
> attributes are not specified either, filter will become NULL, so oops
> will happen(actually nft utility will always set NFTA_OBJ_TABLE attr,
> so I write a test program to make this happen):
> 
>   BUG: unable to handle kernel NULL pointer dereference at (null)
>   IP: nf_tables_dump_obj+0x17c/0x330 [nf_tables]
>   [...]
>   Call Trace:
>   ? nf_tables_dump_obj+0x5/0x330 [nf_tables]
>   ? __kmalloc_reserve.isra.35+0x31/0x90
>   ? __alloc_skb+0x5b/0x1e0
>   netlink_dump+0x124/0x2a0
>   __netlink_dump_start+0x161/0x190
>   nf_tables_getobj+0xe8/0x280 [nf_tables]

Also applied, thanks.