netdev - [patch] irda: precedence bug in irlmp_seq_hb

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Message-ID: <20151019101649.GC26688@mwanda>
Date:	Mon, 19 Oct 2015 13:16:49 +0300
From:	Dan Carpenter <dan.carpenter@...cle.com>
To:	Samuel Ortiz <samuel@...tiz.org>
Cc:	"David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
	security@...nel.org, throber3 <throber3@...il.com>,
	程君(成淼) <chengmiao.cj@...baba-inc.com>
Subject: [patch] irda: precedence bug in irlmp_seq_hb_idx()

This is decrementing the pointer, instead of the value stored in the
pointer.  KASan detects it as an out of bounds reference.

Reported-by: "Berry Cheng 程君(成淼)" <chengmiao.cj@...baba-inc.com>
Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>
---
This bug predates the start of git.  You would think it would have been
reported earlier since it looks like a serious bug.  I cannot test this
so please review carefully.

diff --git a/net/irda/irlmp.c b/net/irda/irlmp.c
index a26c401..4396459 100644
--- a/net/irda/irlmp.c
+++ b/net/irda/irlmp.c
@@ -1839,7 +1839,7 @@ static void *irlmp_seq_hb_idx(struct irlmp_iter_state *iter, loff_t *off)
 	for (element = hashbin_get_first(iter->hashbin);
 	     element != NULL;
 	     element = hashbin_get_next(iter->hashbin)) {
-		if (!off || *off-- == 0) {
+		if (!off || (*off)-- == 0) {
 			/* NB: hashbin left locked */
 			return element;
 		}
--
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