Commit 9b368814 authored Feb 24, 2016 by Linus Lüssing Committed by David S. Miller Feb 25, 2016

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: 9afd85c9 ("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>

parent a4690afe

net/core/skbuff.c

+20 −2

Original line number	Diff line number	Diff line
		@@ -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;

Admin message