linux-kernel - scatterlist.c: bug in sg

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Message-ID: <c384c5ea0809280815l63fab13fqf97a619598f0dd71@mail.gmail.com>
Date:	Sun, 28 Sep 2008 17:15:52 +0200
From:	"Leon Woestenberg" <leon.woestenberg@...il.com>
To:	"FUJITA Tomonori" <fujita.tomonori@....ntt.co.jp>,
	linux-kernel@...r.kernel.org,
	James.Bottomley@...senpartnership.com, jens.axboe@...cle.com
Subject: scatterlist.c: bug in sg_next()?

Hello,

I was code-inspecting 2.6.27-r7 through git web, when I came across this:

In sg_next(), after following a chain_ptr, a few more checks should be
performed.
The rare case exists that the first entry in the chained list is a
last marker, in case NULL must be returned.

Can someone confirm and cook a patch?

struct scatterlist *sg_next(struct scatterlist *sg)
{
  if (sg_is_last(sg))
    return NULL;
  sg++;
  if (unlikely(sg_is_chain(sg))) {
     sg = sg_chain_ptr(sg);
+#ifdef CONFIG_DEBUG_SG
+ BUG_ON(sg->sg_magic != SG_MAGIC);
+#endif
+   if (sg_is_last(sg))
+     return NULL;
  }
  return sg;
}

Signed-off-by: Leon Woestenberg <leon@...ebranch.com>

Regards,
-- 
Leon
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