[Patch net] rds: avoid calling sock_kfree_s() on allocation failure

[Patch net] rds: avoid calling sock_kfree_s() on allocation failure

[Cong Wang]

From: Cong Wang <cwang@twopensource.com>

It is okay to free a NULL pointer but not okay to mischarge the socket optmem
accounting. Compile test only.

Reported-by: rucsoftsec@gmail.com
Cc: Chien Yen <chien.yen@oracle.com>
Cc: Stephen Hemminger <stephen@networkplumber.org>
Signed-off-by: Cong Wang <cwang@twopensource.com>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>

---
diff --git a/net/rds/rdma.c b/net/rds/rdma.c
index 4e37c1c..40084d8 100644
--- a/net/rds/rdma.c
+++ b/net/rds/rdma.c
@@ -564,12 +564,12 @@ int rds_cmsg_rdma_args(struct rds_sock *rs, struct rds_message *rm,
 
 	if (rs->rs_bound_addr == 0) {
 		ret = -ENOTCONN; /* XXX not a great errno */
-		goto out;
+		goto out_ret;
 	}
 
 	if (args->nr_local > UIO_MAXIOV) {
 		ret = -EMSGSIZE;
-		goto out;
+		goto out_ret;
 	}
 
 	/* Check whether to allocate the iovec area */
@@ -578,7 +578,7 @@ int rds_cmsg_rdma_args(struct rds_sock *rs, struct rds_message *rm,
 		iovs = sock_kmalloc(rds_rs_to_sk(rs), iov_size, GFP_KERNEL);
 		if (!iovs) {
 			ret = -ENOMEM;
-			goto out;
+			goto out_ret;
 		}
 	}
 
@@ -696,6 +696,7 @@ int rds_cmsg_rdma_args(struct rds_sock *rs, struct rds_message *rm,
 	if (iovs != iovstack)
 		sock_kfree_s(rds_rs_to_sk(rs), iovs, iov_size);
 	kfree(pages);
+out_ret:
 	if (ret)
 		rds_rdma_free_op(op);
 	else

Re: [Patch net] rds: avoid calling sock_kfree_s() on allocation failure

[David Miller]

From: Cong Wang <xiyou.wangcong@gmail.com>
Date: Tue, 14 Oct 2014 12:35:08 -0700

> From: Cong Wang <cwang@twopensource.com>
> 
> It is okay to free a NULL pointer but not okay to mischarge the socket optmem
> accounting. Compile test only.
> 
> Reported-by: rucsoftsec@gmail.com
> Cc: Chien Yen <chien.yen@oracle.com>
> Cc: Stephen Hemminger <stephen@networkplumber.org>
> Signed-off-by: Cong Wang <cwang@twopensource.com>
> Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>

Applied, and I'm going to add the following bug check to the tree too.

====================
[PATCH] net: Trap attempts to call sock_kfree_s() with a NULL pointer.

Unlike normal kfree() it is never right to call sock_kfree_s() with
a NULL pointer, because sock_kfree_s() also has the side effect of
discharging the memory from the sockets quota.

Signed-off-by: David S. Miller <davem@davemloft.net>
---
 net/core/sock.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/core/sock.c b/net/core/sock.c
index b4f3ea2..15e0c67 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -1718,6 +1718,8 @@ EXPORT_SYMBOL(sock_kmalloc);
  */
 void sock_kfree_s(struct sock *sk, void *mem, int size)
 {
+	if (WARN_ON_ONCE(!mem))
+		return;
 	kfree(mem);
 	atomic_sub(size, &sk->sk_omem_alloc);
 }
-- 
1.7.11.7

Re: [Patch net] rds: avoid calling sock_kfree_s() on allocation failure

[Cong Wang]

On Tue, Oct 14, 2014 at 2:03 PM, David Miller <davem@davemloft.net> wrote:
> From: Cong Wang <xiyou.wangcong@gmail.com>
> Date: Tue, 14 Oct 2014 12:35:08 -0700
>
>> From: Cong Wang <cwang@twopensource.com>
>>
>> It is okay to free a NULL pointer but not okay to mischarge the socket optmem
>> accounting. Compile test only.
>>
>> Reported-by: rucsoftsec@gmail.com
>> Cc: Chien Yen <chien.yen@oracle.com>
>> Cc: Stephen Hemminger <stephen@networkplumber.org>
>> Signed-off-by: Cong Wang <cwang@twopensource.com>
>> Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
>
> Applied, and I'm going to add the following bug check to the tree too.
>
> ====================
> [PATCH] net: Trap attempts to call sock_kfree_s() with a NULL pointer.
>
> Unlike normal kfree() it is never right to call sock_kfree_s() with
> a NULL pointer, because sock_kfree_s() also has the side effect of
> discharging the memory from the sockets quota.
>
> Signed-off-by: David S. Miller <davem@davemloft.net>


Acked-by: Cong Wang <cwang@twopensource.com>

Sounds reasonable. It could catch more bugs similar to this one.

Thanks!