2015-05-26 15:23:25

by Mark Salyzyn

Subject: [PATCH v3] net/unix: sk_socket can disappear when state is unlocked

got a rare NULL pointer dereference in clear_bit

Signed-off-by: Mark Salyzyn <[email protected]>
----
v2: switch to sock_flag(sk, SOCK_DEAD) and added net/caif/caif_socket.c
v3: return -ECONNRESET in upstream caller of wait function for SOCK_DEAD
---
net/caif/caif_socket.c | 8 ++++++++
net/unix/af_unix.c | 8 ++++++++
2 files changed, 16 insertions(+)

diff --git a/net/caif/caif_socket.c b/net/caif/caif_socket.c
index 4ec0c80..112ad78 100644
--- a/net/caif/caif_socket.c
+++ b/net/caif/caif_socket.c
@@ -330,6 +330,10 @@ static long caif_stream_data_wait(struct sock *sk, long timeo)
release_sock(sk);
timeo = schedule_timeout(timeo);
lock_sock(sk);
+
+ if (sock_flag(sk, SOCK_DEAD))
+ break;
+
clear_bit(SOCK_ASYNC_WAITDATA, &sk->sk_socket->flags);
}

@@ -373,6 +377,10 @@ static int caif_stream_recvmsg(struct socket *sock, struct msghdr *msg,
struct sk_buff *skb;

lock_sock(sk);
+ if (sock_flag(sk, SOCK_DEAD)) {
+ err = -ECONNRESET;
+ goto unlock;
+ }
skb = skb_dequeue(&sk->sk_receive_queue);
caif_check_flow_release(sk);

diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index 5266ea7..0643059 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -1880,6 +1880,10 @@ static long unix_stream_data_wait(struct sock *sk, long timeo,
unix_state_unlock(sk);
timeo = freezable_schedule_timeout(timeo);
unix_state_lock(sk);
+
+ if (sock_flag(sk, SOCK_DEAD))
+ break;
+
clear_bit(SOCK_ASYNC_WAITDATA, &sk->sk_socket->flags);
}

@@ -1939,6 +1943,10 @@ static int unix_stream_recvmsg(struct socket *sock, struct msghdr *msg,
struct sk_buff *skb, *last;

unix_state_lock(sk);
+ if (sock_flag(sk, SOCK_DEAD)) {
+ err = -ECONNRESET;
+ goto unlock;
+ }
last = skb = skb_peek(&sk->sk_receive_queue);
again:
if (skb == NULL) {
--
2.2.0.rc0.207.ga3a616c

2015-05-26 21:25:03

by Hannes Frederic Sowa

Subject: Re: [PATCH v3] net/unix: sk_socket can disappear when state is unlocked

Hi,

On Tue, May 26, 2015, at 17:22, Mark Salyzyn wrote:
> got a rare NULL pointer dereference in clear_bit
>
> Signed-off-by: Mark Salyzyn <[email protected]>

IMHO, this is the right approach, I didn't came up with something
easier, thanks!

Acked-by: Hannes Frederic Sowa <[email protected]>

2015-05-27 03:20:06

by David Miller

Subject: Re: [PATCH v3] net/unix: sk_socket can disappear when state is unlocked

From: Hannes Frederic Sowa <[email protected]>
Date: Tue, 26 May 2015 23:24:59 +0200

> On Tue, May 26, 2015, at 17:22, Mark Salyzyn wrote:
>> got a rare NULL pointer dereference in clear_bit
>>
>> Signed-off-by: Mark Salyzyn <[email protected]>
>
> IMHO, this is the right approach, I didn't came up with something
> easier, thanks!
>
> Acked-by: Hannes Frederic Sowa <[email protected]>

Applied and queued up for -stable, thanks!