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netfilter: nf_tables: fix possible oops when dumping stateful objects 

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: a9fea2a3c3 ("netfilter: nf_tables: allow to filter stateful object dumps by type")
Signed-off-by: Liping Zhang <zlpnobody@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
This commit is contained in:
Liping Zhang 2017-01-07 20:51:50 +08:00 committed by Pablo Neira Ayuso
parent 6443ebc3fd
commit d21e540b4d
1 changed files with 3 additions and 2 deletions
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5
net/netfilter/nf_tables_api.c
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@ -4262,10 +4262,11 @@ static int nf_tables_dump_obj(struct sk_buff *skb, struct netlink_callback *cb)
if (idx > s_idx) if (idx > s_idx)
memset(&cb->args[1], 0, memset(&cb->args[1], 0,
sizeof(cb->args) - sizeof(cb->args[0])); sizeof(cb->args) - sizeof(cb->args[0]));
if (filter->table[0] && if (filter && filter->table[0] &&
strcmp(filter->table, table->name)) strcmp(filter->table, table->name))
goto cont; goto cont;
if (filter->type != NFT_OBJECT_UNSPEC && if (filter &&
filter->type != NFT_OBJECT_UNSPEC &&
obj->type->type != filter->type) obj->type->type != filter->type)
goto cont; goto cont;