[PATCH v2] audit: fix memory leak in nf_tables_commit

In nf_tables_commit, if nf_tables_commit_audit_alloc fails, it does not
free the adp variable.

Fix this by freeing the linked list with head adl.

backtrace:
  kmalloc include/linux/slab.h:591 [inline]
  kzalloc include/linux/slab.h:721 [inline]
  nf_tables_commit_audit_alloc net/netfilter/nf_tables_api.c:8439 [inline]
  nf_tables_commit+0x16e/0x1760 net/netfilter/nf_tables_api.c:8508
  nfnetlink_rcv_batch+0x512/0xa80 net/netfilter/nfnetlink.c:562
  nfnetlink_rcv_skb_batch net/netfilter/nfnetlink.c:634 [inline]
  nfnetlink_rcv+0x1fa/0x220 net/netfilter/nfnetlink.c:652
  netlink_unicast_kernel net/netlink/af_netlink.c:1314 [inline]
  netlink_unicast+0x2c7/0x3e0 net/netlink/af_netlink.c:1340
  netlink_sendmsg+0x36b/0x6b0 net/netlink/af_netlink.c:1929
  sock_sendmsg_nosec net/socket.c:702 [inline]
  sock_sendmsg+0x56/0x80 net/socket.c:722

Reported-by: syzbot <redacted>
Reported-by: kernel test robot <redacted>
Fixes: c520292f29b8 ("audit: log nftables configuration change events once per table")
Signed-off-by: Dongliang Mu <redacted>
---
v1->v2: fix the compile issue
 net/netfilter/nf_tables_api.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index 390d4466567f..7f45b291be13 100644
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c

@@ -8444,6 +8444,16 @@ static int nf_tables_commit_audit_alloc(struct list_head *adl,
 	return 0;
 }
 
+static void nf_tables_commit_free(struct list_head *adl)
+{
+	struct nft_audit_data *adp, *adn;
+
+	list_for_each_entry_safe(adp, adn, adl, list) {
+		list_del(&adp->list);
+		kfree(adp);
+	}
+}
+
 static void nf_tables_commit_audit_collect(struct list_head *adl,
 					   struct nft_table *table, u32 op)
 {

@@ -8508,6 +8518,7 @@ static int nf_tables_commit(struct net *net, struct sk_buff *skb)
 		ret = nf_tables_commit_audit_alloc(&adl, trans->ctx.table);
 		if (ret) {
 			nf_tables_commit_chain_prepare_cancel(net);
+			nf_tables_commit_free(&adl);
 			return ret;
 		}
 		if (trans->msg_type == NFT_MSG_NEWRULE ||

@@ -8517,6 +8528,7 @@ static int nf_tables_commit(struct net *net, struct sk_buff *skb)
 			ret = nf_tables_commit_chain_prepare(net, chain);
 			if (ret < 0) {
 				nf_tables_commit_chain_prepare_cancel(net);
+				nf_tables_commit_free(&adl);
 				return ret;
 			}
 		}

-- 
2.25.1

Dongliang Mu [off-list ref] wrote:

nf_tables_commit_audit_free?

Aside from that, there should be a followup patch (for nf-next),
adding empty inline functions in case of CONFIG_AUDITSYSCALL=n.

Right now it does pointless aggregation for the AUDIT=n case.

On Tue, Jul 13, 2021 at 9:21 PM Florian Westphal [off-list ref] wrote:

Dongliang Mu [off-list ref] wrote:

quoted

In nf_tables_commit, if nf_tables_commit_audit_alloc fails, it does not
free the adp variable.

Fix this by freeing the linked list with head adl.

backtrace:
  kmalloc include/linux/slab.h:591 [inline]
  kzalloc include/linux/slab.h:721 [inline]
  nf_tables_commit_audit_alloc net/netfilter/nf_tables_api.c:8439 [inline]
  nf_tables_commit+0x16e/0x1760 net/netfilter/nf_tables_api.c:8508
  nfnetlink_rcv_batch+0x512/0xa80 net/netfilter/nfnetlink.c:562
  nfnetlink_rcv_skb_batch net/netfilter/nfnetlink.c:634 [inline]
  nfnetlink_rcv+0x1fa/0x220 net/netfilter/nfnetlink.c:652
  netlink_unicast_kernel net/netlink/af_netlink.c:1314 [inline]
  netlink_unicast+0x2c7/0x3e0 net/netlink/af_netlink.c:1340
  netlink_sendmsg+0x36b/0x6b0 net/netlink/af_netlink.c:1929
  sock_sendmsg_nosec net/socket.c:702 [inline]
  sock_sendmsg+0x56/0x80 net/socket.c:722

Reported-by: syzbot <redacted>
Reported-by: kernel test robot <redacted>
Fixes: c520292f29b8 ("audit: log nftables configuration change events once per table")
Signed-off-by: Dongliang Mu <redacted>
---
v1->v2: fix the compile issue
 net/netfilter/nf_tables_api.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index 390d4466567f..7f45b291be13 100644
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c

@@ -8444,6 +8444,16 @@ static int nf_tables_commit_audit_alloc(struct list_head *adl,
      return 0;
 }

+static void nf_tables_commit_free(struct list_head *adl)

nf_tables_commit_audit_free?

What do you mean? Modify the name of newly added function to
nf_tables_commit_audit_free?

Aside from that, there should be a followup patch (for nf-next),
adding empty inline functions in case of CONFIG_AUDITSYSCALL=n.

I see. I prefer to send them (two implementations of the newly added
function) in version v2.

Right now it does pointless aggregation for the AUDIT=n case.

Dongliang Mu [off-list ref] wrote:

quoted

quoted

+static void nf_tables_commit_free(struct list_head *adl)

nf_tables_commit_audit_free?

What do you mean? Modify the name of newly added function to
nf_tables_commit_audit_free?

Yes, this function is audit related, and it does the inverse
of existing '...audit_alloc'.

On Tue, Jul 13, 2021 at 11:31 PM Florian Westphal [off-list ref] wrote:

Dongliang Mu [off-list ref] wrote:

quoted

quoted

quoted

+static void nf_tables_commit_free(struct list_head *adl)

nf_tables_commit_audit_free?

What do you mean? Modify the name of newly added function to
nf_tables_commit_audit_free?

Yes, this function is audit related, and it does the inverse
of existing '...audit_alloc'.

Hi Florian,

I double-check the patch, and it seems there is no need to send a
followup patch (nf-next).

I will send a v3 patch with the new function name.

Best regards
Dongliang Mu