* [PATCH net v2] __netif_receive_skb_core: pass skb by reference
@ 2020-05-19 7:32 Boris Sukholitko
2020-05-19 14:18 ` Edward Cree
2020-05-19 22:39 ` David Miller
0 siblings, 2 replies; 3+ messages in thread
From: Boris Sukholitko @ 2020-05-19 7:32 UTC (permalink / raw)
To: netdev
__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 <boris.sukholitko@broadcom.com>
---
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 6d327b7aa813..38adb56624f7 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -4988,7 +4988,7 @@ 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;
@@ -4997,6 +4997,7 @@ static int __netif_receive_skb_core(struct sk_buff *skb, bool pfmemalloc,
bool deliver_exact = false;
int ret = NET_RX_DROP;
__be16 type;
+ struct sk_buff *skb = *pskb;
net_timestamp_check(!netdev_tstamp_prequeue, skb);
@@ -5023,8 +5024,10 @@ 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);
}
@@ -5174,6 +5177,13 @@ 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;
}
@@ -5183,7 +5193,7 @@ 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 = INDIRECT_CALL_INET(pt_prev->func, ipv6_rcv, ip_rcv, skb,
skb->dev, pt_prev, orig_dev);
@@ -5261,7 +5271,7 @@ 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) {
--
2.19.2
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH net v2] __netif_receive_skb_core: pass skb by reference
2020-05-19 7:32 [PATCH net v2] __netif_receive_skb_core: pass skb by reference Boris Sukholitko
@ 2020-05-19 14:18 ` Edward Cree
2020-05-19 22:39 ` David Miller
1 sibling, 0 replies; 3+ messages in thread
From: Edward Cree @ 2020-05-19 14:18 UTC (permalink / raw)
To: Boris Sukholitko, netdev
On 19/05/2020 08:32, Boris Sukholitko wrote:
> __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 <boris.sukholitko@broadcom.com>
> ---
> 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 6d327b7aa813..38adb56624f7 100644
> --- a/net/core/dev.c
> +++ b/net/core/dev.c
> @@ -4988,7 +4988,7 @@ 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;
> @@ -4997,6 +4997,7 @@ static int __netif_receive_skb_core(struct sk_buff *skb, bool pfmemalloc,
> bool deliver_exact = false;
> int ret = NET_RX_DROP;
> __be16 type;
> + struct sk_buff *skb = *pskb;
Reverse christmas tree here, or else David will complain ;-)
Apart from that,
Acked-by: Edward Cree <ecree@solarflare.com>
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH net v2] __netif_receive_skb_core: pass skb by reference
2020-05-19 7:32 [PATCH net v2] __netif_receive_skb_core: pass skb by reference Boris Sukholitko
2020-05-19 14:18 ` Edward Cree
@ 2020-05-19 22:39 ` David Miller
1 sibling, 0 replies; 3+ messages in thread
From: David Miller @ 2020-05-19 22:39 UTC (permalink / raw)
To: boris.sukholitko; +Cc: netdev
From: Boris Sukholitko <boris.sukholitko@broadcom.com>
Date: Tue, 19 May 2020 10:32:37 +0300
> __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 <boris.sukholitko@broadcom.com>
Applied and queued up for -stable.
> @@ -4997,6 +4997,7 @@ static int __netif_receive_skb_core(struct sk_buff *skb, bool pfmemalloc,
> bool deliver_exact = false;
> int ret = NET_RX_DROP;
> __be16 type;
> + struct sk_buff *skb = *pskb;
I fixed up the reverse christmas tree variable ordering here, please take
care in this area next time.
Thank you.
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2020-05-19 22:39 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
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2020-05-19 7:32 [PATCH net v2] __netif_receive_skb_core: pass skb by reference Boris Sukholitko
2020-05-19 14:18 ` Edward Cree
2020-05-19 22:39 ` David Miller
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