From: Soheil Hassas Yeganeh <soh...@google.com>
__sock_recv_timestamp can be called for both normal skbs (for
receive timestamps) and for skbs on the error queue (for transmit
timestamps).
Commit 1c885808e456
(tcp: SOF_TIMESTAMPING_OPT_STATS option for SO_TIMESTAMPING)
assumes any skb passed to __sock_recv_timestamp are from
the error queue, containing OPT_STATS in the content of the skb.
This results in accessing invalid memory or generating junk
data.
To fix this, set skb->pkt_type to PACKET_OUTGOING for packets
on the error queue. This is safe because on the receive path
on local sockets skb->pkt_type is never set to PACKET_OUTGOING.
With that, copy OPT_STATS from a packet, only if its pkt_type
is PACKET_OUTGOING.
Fixes: 1c885808e456 ("tcp: SOF_TIMESTAMPING_OPT_STATS option for
SO_TIMESTAMPING")
Reported-by: JongHwan Kim <zzoru...@gmail.com>
Signed-off-by: Soheil Hassas Yeganeh <soh...@google.com>
Signed-off-by: Eric Dumazet <eduma...@google.com>
Signed-off-by: Willem de Bruijn <will...@google.com>
---
net/core/skbuff.c | 10 ++++++++++
net/socket.c | 13 ++++++++++++-
2 files changed, 22 insertions(+), 1 deletion(-)
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index cd4ba8c6b609..b1fbd1958eb6 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -3694,6 +3694,15 @@ static void sock_rmem_free(struct sk_buff *skb)
atomic_sub(skb->truesize, &sk->sk_rmem_alloc);
}
+static void skb_set_err_queue(struct sk_buff *skb)
+{
+ /* pkt_type of skbs received on local sockets is never PACKET_OUTGOING.
+ * So, it is safe to (mis)use it to mark skbs on the error queue.
+ */
+ skb->pkt_type = PACKET_OUTGOING;
+ BUILD_BUG_ON(PACKET_OUTGOING == 0);
+}
+
/*
* Note: We dont mem charge error packets (no sk_forward_alloc changes)
*/
@@ -3707,6 +3716,7 @@ int sock_queue_err_skb(struct sock *sk, struct sk_buff
*skb)
skb->sk = sk;
skb->destructor = sock_rmem_free;
atomic_add(skb->truesize, &sk->sk_rmem_alloc);
+ skb_set_err_queue(skb);
/* before exiting rcu section, make sure dst is refcounted */
skb_dst_force(skb);
diff --git a/net/socket.c b/net/socket.c
index e034fe4164be..692d6989d2c2 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -652,6 +652,16 @@ int kernel_sendmsg(struct socket *sock, struct msghdr *msg,
}
EXPORT_SYMBOL(kernel_sendmsg);
+static bool skb_is_err_queue(const struct sk_buff *skb)
+{
+ /* pkt_type of skbs enqueued on the error queue are set to
+ * PACKET_OUTGOING in skb_set_err_queue(). This is only safe to do
+ * in recvmsg, since skbs received on a local socket will never
+ * have a pkt_type of PACKET_OUTGOING.
+ */
+ return skb->pkt_type == PACKET_OUTGOING;
+}
+
/*
* called from sock_recv_timestamp() if sock_flag(sk, SOCK_RCVTSTAMP)
*/
@@ -695,7 +705,8 @@ void __sock_recv_timestamp(struct msghdr *msg, struct sock
*sk,
put_cmsg(msg, SOL_SOCKET,
SCM_TIMESTAMPING, sizeof(tss), &tss);
- if (skb->len && (sk->sk_tsflags & SOF_TIMESTAMPING_OPT_STATS))
+ if (skb_is_err_queue(skb) && skb->len &&
+ (sk->sk_tsflags & SOF_TIMESTAMPING_OPT_STATS))
put_cmsg(msg, SOL_SOCKET, SCM_TIMESTAMPING_OPT_STATS,
skb->len, skb->data);
}
--
2.12.0.367.g23dc2f6d3c-goog
