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authorBen Hutchings <bhutchings@solarflare.com>2012-07-30 15:57:00 +0000
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2012-10-02 10:29:34 -0700
commit2dc3b21fbca98bd3c8d9e53acf5d966add3c7606 (patch)
tree6fe9f88dec40cfca839962a5a363848b27afb744 /include
parent00709f7f01c3a10252f030f0bdacecbb349d7be4 (diff)
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net: Allow driver to limit number of GSO segments per skb
[ Upstream commit 30b678d844af3305cda5953467005cebb5d7b687 ] A peer (or local user) may cause TCP to use a nominal MSS of as little as 88 (actual MSS of 76 with timestamps). Given that we have a sufficiently prodigious local sender and the peer ACKs quickly enough, it is nevertheless possible to grow the window for such a connection to the point that we will try to send just under 64K at once. This results in a single skb that expands to 861 segments. In some drivers with TSO support, such an skb will require hundreds of DMA descriptors; a substantial fraction of a TX ring or even more than a full ring. The TX queue selected for the skb may stall and trigger the TX watchdog repeatedly (since the problem skb will be retried after the TX reset). This particularly affects sfc, for which the issue is designated as CVE-2012-3412. Therefore: 1. Add the field net_device::gso_max_segs holding the device-specific limit. 2. In netif_skb_features(), if the number of segments is too high then mask out GSO features to force fall back to software GSO. Signed-off-by: Ben Hutchings <bhutchings@solarflare.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'include')
-rw-r--r--include/linux/netdevice.h2
1 files changed, 2 insertions, 0 deletions
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 33900a53c99..79596d6dd85 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -1279,6 +1279,8 @@ struct net_device {
/* for setting kernel sock attribute on TCP connection setup */
#define GSO_MAX_SIZE 65536
unsigned int gso_max_size;
+#define GSO_MAX_SEGS 65535
+ u16 gso_max_segs;
#ifdef CONFIG_DCB
/* Data Center Bridging netlink ops */