Subject: Re: [PATCH] IB/IPoIB: Check the headroom size

From: Paolo Abeni <[email-masked]>
Date: Wed, 26 Apr 2017 09:46:34 +0200

On Wed, 2017-04-26 at 00:50 +0300, Or Gerlitz wrote:
> so maybe @ least for the time being, we should be picking Hong's patch
> with proper change log and without the giant stack dump till we have
> something better. If you agree, can you do the re-write of the change
> log?

I think that Hong's patch is following the correct way to fix the
issue: ipoib_hard_header() can't assume that the skb headroom is at
least IPOIB_HARD_LEN bytes, as wrongly implied by commit fc791b633515
(my fault, I'm sorry).

Perhaps we can make the code a little more robust with something
alongside the following (only compile tested):
---
diff --git a/drivers/infiniband/ulp/ipoib/ipoib_main.c b/drivers/infiniband/ulp/ipoib/ipoib_main.c
index d1d3fb7..d53d2e1 100644
--- a/drivers/infiniband/ulp/ipoib/ipoib_main.c
+++ b/drivers/infiniband/ulp/ipoib/ipoib_main.c
@@ -1160,6 +1160,11 @@ static int ipoib_hard_header(struct sk_buff *skb,
                             const void *daddr, const void *saddr, unsigned len)
 {
        struct ipoib_header *header;
+       int ret;
+
+       ret = skb_cow_head(skb, IPOIB_HARD_LEN);
+       if (ret)
+               return ret;
 
        header = (struct ipoib_header *) skb_push(skb, sizeof *header);
---

Paolo
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