linux-kernel - [169/289] netfilter: NF_HOOK

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Message-Id: <20101208005738.371418861@clark.site>
Date:	Tue, 07 Dec 2010 16:59:06 -0800
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...nel.org
Cc:	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Eric Paris <eparis@...hat.com>,
	Patrick McHardy <kaber@...sh.net>
Subject: [169/289] netfilter: NF_HOOK_COND has wrong conditional

2.6.36-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Eric Paris <eparis@...hat.com>

commit ac5aa2e3332ec04889074afdbd1479424d0227a5 upstream.

The NF_HOOK_COND returns 0 when it shouldn't due to what I believe to be an
error in the code as the order of operations is not what was intended.  C will
evalutate == before =.  Which means ret is getting set to the bool result,
rather than the return value of the function call.  The code says

if (ret = function() == 1)
when it meant to say:
if ((ret = function()) == 1)

Normally the compiler would warn, but it doesn't notice it because its
a actually complex conditional and so the wrong code is wrapped in an explict
set of () [exactly what the compiler wants you to do if this was intentional].
Fixing this means that errors when netfilter denies a packet get propagated
back up the stack rather than lost.

Problem introduced by commit 2249065f (netfilter: get rid of the grossness
in netfilter.h).

Signed-off-by: Eric Paris <eparis@...hat.com>
Signed-off-by: Patrick McHardy <kaber@...sh.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

---
 include/linux/netfilter.h |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/include/linux/netfilter.h
+++ b/include/linux/netfilter.h
@@ -215,7 +215,7 @@ NF_HOOK_COND(uint8_t pf, unsigned int ho
 	int ret;

 	if (!cond ||
-	    (ret = nf_hook_thresh(pf, hook, skb, in, out, okfn, INT_MIN) == 1))
+	    ((ret = nf_hook_thresh(pf, hook, skb, in, out, okfn, INT_MIN)) == 1))
 		ret = okfn(skb);
 	return ret;
 }

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