From 08ea4ff33d782f7f2924644d122b6fcb9d43abff Mon Sep 17 00:00:00 2001 From: Dongli Zhang Date: Mon, 16 Sep 2019 11:46:59 +0800 Subject: xen-netfront: do not assume sk_buff_head list is empty in error handling [ Upstream commit 00b368502d18f790ab715e055869fd4bb7484a9b ] When skb_shinfo(skb) is not able to cache extra fragment (that is, skb_shinfo(skb)->nr_frags >= MAX_SKB_FRAGS), xennet_fill_frags() assumes the sk_buff_head list is already empty. As a result, cons is increased only by 1 and returns to error handling path in xennet_poll(). However, if the sk_buff_head list is not empty, queue->rx.rsp_cons may be set incorrectly. That is, queue->rx.rsp_cons would point to the rx ring buffer entries whose queue->rx_skbs[i] and queue->grant_rx_ref[i] are already cleared to NULL. This leads to NULL pointer access in the next iteration to process rx ring buffer entries. Below is how xennet_poll() does error handling. All remaining entries in tmpq are accounted to queue->rx.rsp_cons without assuming how many outstanding skbs are remained in the list. 985 static int xennet_poll(struct napi_struct *napi, int budget) ... ... 1032 if (unlikely(xennet_set_skb_gso(skb, gso))) { 1033 __skb_queue_head(&tmpq, skb); 1034 queue->rx.rsp_cons += skb_queue_len(&tmpq); 1035 goto err; 1036 } It is better to always have the error handling in the same way. Fixes: ad4f15dc2c70 ("xen/netfront: don't bug in case of too many frags") Signed-off-by: Dongli Zhang Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- drivers/net/xen-netfront.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'drivers/net/xen-netfront.c') diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c index 14ceeaaa7fe5..c31c564b8eab 100644 --- a/drivers/net/xen-netfront.c +++ b/drivers/net/xen-netfront.c @@ -907,7 +907,7 @@ static RING_IDX xennet_fill_frags(struct netfront_queue *queue, __pskb_pull_tail(skb, pull_to - skb_headlen(skb)); } if (unlikely(skb_shinfo(skb)->nr_frags >= MAX_SKB_FRAGS)) { - queue->rx.rsp_cons = ++cons; + queue->rx.rsp_cons = ++cons + skb_queue_len(list); kfree_skb(nskb); return ~0U; } -- cgit v1.2.3 From d51c3f70633bf1e84559f9bbe54846e8b20968dc Mon Sep 17 00:00:00 2001 From: Dongli Zhang Date: Tue, 1 Oct 2019 21:56:41 +0800 Subject: xen-netfront: do not use ~0U as error return value for xennet_fill_frags() [ Upstream commit a761129e3625688310aecf26e1be9e98e85f8eb5 ] xennet_fill_frags() uses ~0U as return value when the sk_buff is not able to cache extra fragments. This is incorrect because the return type of xennet_fill_frags() is RING_IDX and 0xffffffff is an expected value for ring buffer index. In the situation when the rsp_cons is approaching 0xffffffff, the return value of xennet_fill_frags() may become 0xffffffff which xennet_poll() (the caller) would regard as error. As a result, queue->rx.rsp_cons is set incorrectly because it is updated only when there is error. If there is no error, xennet_poll() would be responsible to update queue->rx.rsp_cons. Finally, queue->rx.rsp_cons would point to the rx ring buffer entries whose queue->rx_skbs[i] and queue->grant_rx_ref[i] are already cleared to NULL. This leads to NULL pointer access in the next iteration to process rx ring buffer entries. The symptom is similar to the one fixed in commit 00b368502d18 ("xen-netfront: do not assume sk_buff_head list is empty in error handling"). This patch changes the return type of xennet_fill_frags() to indicate whether it is successful or failed. The queue->rx.rsp_cons will be always updated inside this function. Fixes: ad4f15dc2c70 ("xen/netfront: don't bug in case of too many frags") Signed-off-by: Dongli Zhang Reviewed-by: Juergen Gross Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- drivers/net/xen-netfront.c | 17 +++++++++-------- 1 file changed, 9 insertions(+), 8 deletions(-) (limited to 'drivers/net/xen-netfront.c') diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c index c31c564b8eab..6d391a268469 100644 --- a/drivers/net/xen-netfront.c +++ b/drivers/net/xen-netfront.c @@ -888,9 +888,9 @@ static int xennet_set_skb_gso(struct sk_buff *skb, return 0; } -static RING_IDX xennet_fill_frags(struct netfront_queue *queue, - struct sk_buff *skb, - struct sk_buff_head *list) +static int xennet_fill_frags(struct netfront_queue *queue, + struct sk_buff *skb, + struct sk_buff_head *list) { RING_IDX cons = queue->rx.rsp_cons; struct sk_buff *nskb; @@ -909,7 +909,7 @@ static RING_IDX xennet_fill_frags(struct netfront_queue *queue, if (unlikely(skb_shinfo(skb)->nr_frags >= MAX_SKB_FRAGS)) { queue->rx.rsp_cons = ++cons + skb_queue_len(list); kfree_skb(nskb); - return ~0U; + return -ENOENT; } skb_add_rx_frag(skb, skb_shinfo(skb)->nr_frags, @@ -920,7 +920,9 @@ static RING_IDX xennet_fill_frags(struct netfront_queue *queue, kfree_skb(nskb); } - return cons; + queue->rx.rsp_cons = cons; + + return 0; } static int checksum_setup(struct net_device *dev, struct sk_buff *skb) @@ -1046,8 +1048,7 @@ err: skb->data_len = rx->status; skb->len += rx->status; - i = xennet_fill_frags(queue, skb, &tmpq); - if (unlikely(i == ~0U)) + if (unlikely(xennet_fill_frags(queue, skb, &tmpq))) goto err; if (rx->flags & XEN_NETRXF_csum_blank) @@ -1057,7 +1058,7 @@ err: __skb_queue_tail(&rxq, skb); - queue->rx.rsp_cons = ++i; + i = ++queue->rx.rsp_cons; work_done++; } -- cgit v1.2.3