net: fix bridge multicast packet checksum validation

We need to update the skb->csum after pulling the skb, otherwise
an unnecessary checksum (re)computation can ocure for IGMP/MLD packets
in the bridge code. Additionally this fixes the following splats for
network devices / bridge ports with support for and enabled RX checksum
offloading:

[...]
[   43.986968] eth0: hw csum failure
[   43.990344] CPU: 3 PID: 0 Comm: swapper/3 Not tainted 4.4.0 #2
[   43.996193] Hardware name: BCM2709
[   43.999647] [<800204e0>] (unwind_backtrace) from [<8001cf14>] (show_stack+0x10/0x14)
[   44.007432] [<8001cf14>] (show_stack) from [<801ab614>] (dump_stack+0x80/0x90)
[   44.014695] [<801ab614>] (dump_stack) from [<802e4548>] (__skb_checksum_complete+0x6c/0xac)
[   44.023090] [<802e4548>] (__skb_checksum_complete) from [<803a055c>] (ipv6_mc_validate_checksum+0x104/0x178)
[   44.032959] [<803a055c>] (ipv6_mc_validate_checksum) from [<802e111c>] (skb_checksum_trimmed+0x130/0x188)
[   44.042565] [<802e111c>] (skb_checksum_trimmed) from [<803a06e8>] (ipv6_mc_check_mld+0x118/0x338)
[   44.051501] [<803a06e8>] (ipv6_mc_check_mld) from [<803b2c98>] (br_multicast_rcv+0x5dc/0xd00)
[   44.060077] [<803b2c98>] (br_multicast_rcv) from [<803aa510>] (br_handle_frame_finish+0xac/0x51c)
[...]

Fixes: 9afd85c9e455 ("net: Export IGMP/MLD message validation code")
Reported-by: Álvaro Fernández Rojas <noltari@gmail.com>
Signed-off-by: Linus Lüssing <linus.luessing@c0d3.blue>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 5bf88f58bee7405ff65f80487a64339b92a91bcb..8616d1147c938808da752734b6cecea260b149b9 100644 (file)
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -2947,6 +2947,24 @@ int skb_append_pagefrags(struct sk_buff *skb, struct page *page,
 }
 EXPORT_SYMBOL_GPL(skb_append_pagefrags);
 
+/**
+ *     skb_push_rcsum - push skb and update receive checksum
+ *     @skb: buffer to update
+ *     @len: length of data pulled
+ *
+ *     This function performs an skb_push on the packet and updates
+ *     the CHECKSUM_COMPLETE checksum.  It should be used on
+ *     receive path processing instead of skb_push unless you know
+ *     that the checksum difference is zero (e.g., a valid IP header)
+ *     or you are setting ip_summed to CHECKSUM_NONE.
+ */
+static unsigned char *skb_push_rcsum(struct sk_buff *skb, unsigned len)
+{
+       skb_push(skb, len);
+       skb_postpush_rcsum(skb, skb->data, len);
+       return skb->data;
+}
+
 /**
  *     skb_pull_rcsum - pull skb and update receive checksum
  *     @skb: buffer to update
@@ -4084,9 +4102,9 @@ struct sk_buff *skb_checksum_trimmed(struct sk_buff *skb,
        if (!pskb_may_pull(skb_chk, offset))
                goto err;
 
-       __skb_pull(skb_chk, offset);
+       skb_pull_rcsum(skb_chk, offset);
        ret = skb_chkf(skb_chk);
-       __skb_push(skb_chk, offset);
+       skb_push_rcsum(skb_chk, offset);
 
        if (ret)
                goto err;