This is a note to let you know that I've just added the patch titled
net: fix bridge multicast packet checksum validation
to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
net-fix-bridge-multicast-packet-checksum-validation.patch
and it can be found in the queue-4.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From foo@baz Sat Apr 16 10:02:53 PDT 2016
From: =?UTF-8?q?Linus=20L=C3=BCssing?= <linus.luessing@xxxxxxxxx>
Date: Wed, 24 Feb 2016 04:21:42 +0100
Subject: net: fix bridge multicast packet checksum validation
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From: =?UTF-8?q?Linus=20L=C3=BCssing?= <linus.luessing@xxxxxxxxx>
[ Upstream commit 9b368814b336b0a1a479135eb2815edbc00efd3c ]
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@xxxxxxxxx>
Signed-off-by: Linus Lüssing <linus.luessing@xxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
include/linux/skbuff.h | 17 +++++++++++++++++
net/core/skbuff.c | 22 ++++++++++++++++++++--
2 files changed, 37 insertions(+), 2 deletions(-)
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -2724,6 +2724,23 @@ static inline void skb_postpull_rcsum(st
unsigned char *skb_pull_rcsum(struct sk_buff *skb, unsigned int len);
+static inline void skb_postpush_rcsum(struct sk_buff *skb,
+ const void *start, unsigned int len)
+{
+ /* For performing the reverse operation to skb_postpull_rcsum(),
+ * we can instead of ...
+ *
+ * skb->csum = csum_add(skb->csum, csum_partial(start, len, 0));
+ *
+ * ... just use this equivalent version here to save a few
+ * instructions. Feeding csum of 0 in csum_partial() and later
+ * on adding skb->csum is equivalent to feed skb->csum in the
+ * first place.
+ */
+ if (skb->ip_summed == CHECKSUM_COMPLETE)
+ skb->csum = csum_partial(start, len, skb->csum);
+}
+
/**
* pskb_trim_rcsum - trim received skb and update checksum
* @skb: buffer to trim
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -2948,6 +2948,24 @@ int skb_append_pagefrags(struct sk_buff
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
* @len: length of data pulled
@@ -4084,9 +4102,9 @@ struct sk_buff *skb_checksum_trimmed(str
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;
Patches currently in stable-queue which might be from linus.luessing@xxxxxxxxx are
queue-4.4/net-fix-bridge-multicast-packet-checksum-validation.patch
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