From 48ec949ac979b4b42d740f67b6177797af834f80 Mon Sep 17 00:00:00 2001 From: Bjorn Andersson Date: Wed, 21 Apr 2021 10:40:07 -0700 Subject: [PATCH] net: qrtr: Avoid potential use after free in MHI send commit 47a017f33943278570c072bc71681809b2567b3a upstream. It is possible that the MHI ul_callback will be invoked immediately following the queueing of the skb for transmission, leading to the callback decrementing the refcount of the associated sk and freeing the skb. As such the dereference of skb and the increment of the sk refcount must happen before the skb is queued, to avoid the skb to be used after free and potentially the sk to drop its last refcount.. Fixes: 6e728f321393 ("net: qrtr: Add MHI transport layer") Signed-off-by: Bjorn Andersson Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- net/qrtr/mhi.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/net/qrtr/mhi.c b/net/qrtr/mhi.c index ff0c41467fc1..0fe4bf40919d 100644 --- a/net/qrtr/mhi.c +++ b/net/qrtr/mhi.c @@ -50,6 +50,9 @@ static int qcom_mhi_qrtr_send(struct qrtr_endpoint *ep, struct sk_buff *skb) struct qrtr_mhi_dev *qdev = container_of(ep, struct qrtr_mhi_dev, ep); int rc; + if (skb->sk) + sock_hold(skb->sk); + rc = skb_linearize(skb); if (rc) goto free_skb; @@ -59,12 +62,11 @@ static int qcom_mhi_qrtr_send(struct qrtr_endpoint *ep, struct sk_buff *skb) if (rc) goto free_skb; - if (skb->sk) - sock_hold(skb->sk); - return rc; free_skb: + if (skb->sk) + sock_put(skb->sk); kfree_skb(skb); return rc;