Re: [Bug #16626] Machine hangs with EIP at skb_copy_and_csum_dev
From: Herbert Xu <hidden>
Date: 2010-09-03 08:30:48
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On Wed, Sep 01, 2010 at 12:50:51PM +0200, Eric Dumazet wrote:
Plamen, could you test following patch ? I reproduced problem on a dev machine and following patch cured it. Thanks [PATCH] gro: fix different skb headrooms packets entering GRO might have different headrooms, even for a given flow (because of implementation details in drivers, like copybreak). We cant force drivers to deliver packets with a fixed headroom. 1) fix skb_segment() skb_segment() makes the false assumption headrooms of fragments are same than the head. When CHECKSUM_PARTIAL is used, this can give csum_start errors, and crash later in skb_copy_and_csum_dev() 2) allocate a minimal skb for head of frag_list skb_gro_receive() uses netdev_alloc_skb(headroom + skb_gro_offset(p)) to allocate a fresh skb. This adds NET_SKB_PAD to a padding already provided by netdevice, depending on various things, like copybreak. Use alloc_skb() to allocate an exact padding, to reduce cache line needs: NET_SKB_PAD + NET_IP_ALIGN bugzilla : https://bugzilla.kernel.org/show_bug.cgi?id=16626 Many thanks to Plamen Petrov, testing many debugging patches ! With help of Jarek Poplawski. Reported-by: Plamen Petrov <redacted> Signed-off-by: Eric Dumazet <redacted> CC: Jarek Poplawski <redacted>
Thanks for diagnosing and fixing this!
quoted hunk ↗ jump to hunk
diff --git a/net/core/skbuff.c b/net/core/skbuff.c index 3a2513f..26396ff 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c@@ -2573,6 +2573,10 @@ struct sk_buff *skb_segment(struct sk_buff *skb, int features) __copy_skb_header(nskb, skb); nskb->mac_len = skb->mac_len; + /* nskb and skb might have different headroom */ + if (nskb->ip_summed == CHECKSUM_PARTIAL) + nskb->csum_start += skb_headroom(nskb) - headroom;
This test is redundant since we require CHECKSUM_PARTIAL for GSO packets. Cheers, -- Email: Herbert Xu [off-list ref] Home Page: http://gondor.apana.org.au/~herbert/ PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt