From 4e4c0fe696b913c0bc89f5eddb11bd8bb03b9a58 Mon Sep 17 00:00:00 2001 From: Boris Sukholitko Date: Tue, 22 Sep 2020 10:15:05 +0800 Subject: [PATCH] __netif_receive_skb_core: pass skb by reference stable inclusion from linux-4.19.126 commit 96b2f1c0b073734d42b2cb38bdd59b945c78d51f -------------------------------- [ Upstream commit c0bbbdc32febd4f034ecbf3ea17865785b2c0652 ] __netif_receive_skb_core may change the skb pointer passed into it (e.g. in rx_handler). The original skb may be freed as a result of this operation. The callers of __netif_receive_skb_core may further process original skb by using pt_prev pointer returned by __netif_receive_skb_core thus leading to unpleasant effects. The solution is to pass skb by reference into __netif_receive_skb_core. v2: Added Fixes tag and comment regarding ppt_prev and skb invariant. Fixes: 88eb1944e18c ("net: core: propagate SKB lists through packet_type lookup") Signed-off-by: Boris Sukholitko Acked-by: Edward Cree Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman Signed-off-by: Yang Yingliang Signed-off-by: Li Aichun Reviewed-by: guodeqing Signed-off-by: Yang Yingliang --- net/core/dev.c | 20 +++++++++++++++----- 1 file changed, 15 insertions(+), 5 deletions(-) diff --git a/net/core/dev.c b/net/core/dev.c index 9ccc14200b80..50498a75c04b 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -4778,11 +4778,12 @@ static inline int nf_ingress(struct sk_buff *skb, struct packet_type **pt_prev, return 0; } -static int __netif_receive_skb_core(struct sk_buff *skb, bool pfmemalloc, +static int __netif_receive_skb_core(struct sk_buff **pskb, bool pfmemalloc, struct packet_type **ppt_prev) { struct packet_type *ptype, *pt_prev; rx_handler_func_t *rx_handler; + struct sk_buff *skb = *pskb; struct net_device *orig_dev; bool deliver_exact = false; int ret = NET_RX_DROP; @@ -4813,8 +4814,10 @@ static int __netif_receive_skb_core(struct sk_buff *skb, bool pfmemalloc, ret2 = do_xdp_generic(rcu_dereference(skb->dev->xdp_prog), skb); preempt_enable(); - if (ret2 != XDP_PASS) - return NET_RX_DROP; + if (ret2 != XDP_PASS) { + ret = NET_RX_DROP; + goto out; + } skb_reset_mac_len(skb); } @@ -4936,6 +4939,13 @@ static int __netif_receive_skb_core(struct sk_buff *skb, bool pfmemalloc, } out: + /* The invariant here is that if *ppt_prev is not NULL + * then skb should also be non-NULL. + * + * Apparently *ppt_prev assignment above holds this invariant due to + * skb dereferencing near it. + */ + *pskb = skb; return ret; } @@ -4945,7 +4955,7 @@ static int __netif_receive_skb_one_core(struct sk_buff *skb, bool pfmemalloc) struct packet_type *pt_prev = NULL; int ret; - ret = __netif_receive_skb_core(skb, pfmemalloc, &pt_prev); + ret = __netif_receive_skb_core(&skb, pfmemalloc, &pt_prev); if (pt_prev) ret = pt_prev->func(skb, skb->dev, pt_prev, orig_dev); return ret; @@ -5021,7 +5031,7 @@ static void __netif_receive_skb_list_core(struct list_head *head, bool pfmemallo struct packet_type *pt_prev = NULL; skb_list_del_init(skb); - __netif_receive_skb_core(skb, pfmemalloc, &pt_prev); + __netif_receive_skb_core(&skb, pfmemalloc, &pt_prev); if (!pt_prev) continue; if (pt_curr != pt_prev || od_curr != orig_dev) { -- GitLab