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net: core: fix uses-after-free in list processing

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In netif_receive_skb_list_internal(), all of skb_defer_rx_timestamp(),
 do_xdp_generic() and enqueue_to_backlog() can lead to kfree(skb).  Thus,
 we cannot wait until after they return to remove the skb from the list;
 instead, we remove it first and, in the pass case, add it to a sublist
 afterwards.
In the case of enqueue_to_backlog() we have already decided not to pass
 when we call the function, so we do not need a sublist.

Fixes: 7da517a3bc ("net: core: Another step of skb receive list processing")
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Edward Cree <ecree@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Edward Cree 2018-07-09 18:09:54 +01:00 committed by David S. Miller
parent c47078d6a3
commit 8c057efaeb
1 changed files with 13 additions and 8 deletions
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21
net/core/dev.c
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@ -4982,25 +4982,30 @@ static void netif_receive_skb_list_internal(struct list_head *head)
{
struct bpf_prog *xdp_prog = NULL;
struct sk_buff *skb, *next;
struct list_head sublist;
INIT_LIST_HEAD(&sublist);
list_for_each_entry_safe(skb, next, head, list) {
net_timestamp_check(netdev_tstamp_prequeue, skb);
if (skb_defer_rx_timestamp(skb))
/* Handled, remove from list */
list_del(&skb->list);
list_del(&skb->list);
if (!skb_defer_rx_timestamp(skb))
list_add_tail(&skb->list, &sublist);
}
list_splice_init(&sublist, head);
if (static_branch_unlikely(&generic_xdp_needed_key)) {
preempt_disable();
rcu_read_lock();
list_for_each_entry_safe(skb, next, head, list) {
xdp_prog = rcu_dereference(skb->dev->xdp_prog);
if (do_xdp_generic(xdp_prog, skb) != XDP_PASS)
/* Dropped, remove from list */
list_del(&skb->list);
list_del(&skb->list);
if (do_xdp_generic(xdp_prog, skb) == XDP_PASS)
list_add_tail(&skb->list, &sublist);
}
rcu_read_unlock();
preempt_enable();
/* Put passed packets back on main list */
list_splice_init(&sublist, head);
}
rcu_read_lock();
@ -5011,9 +5016,9 @@ static void netif_receive_skb_list_internal(struct list_head *head)
int cpu = get_rps_cpu(skb->dev, skb, &rflow);
if (cpu >= 0) {
enqueue_to_backlog(skb, cpu, &rflow->last_qtail);
/* Handled, remove from list */
/* Will be handled, remove from list */
list_del(&skb->list);
enqueue_to_backlog(skb, cpu, &rflow->last_qtail);
}
}
}