linux-kernel - [PATCH] drivers/mtd/ubi: Bad IS

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Date:	Fri, 26 Sep 2008 15:27:25 +0200
From:	Julien Brunel <brunel@...u.dk>
To:	haver@...t.ibm.com, dedekind@...radead.org,
	linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org,
	kernel-janitors@...r.kernel.org
Subject: [PATCH] drivers/mtd/ubi: Bad IS_ERR test

In case of error, the function add_volume returns an ERR pointer. The
result of IS_ERR, which is supposed to be used in a test as it is, is
here checked to be less than zero, which seems odd. We suggest to
replace this test by a simple IS_ERR test.

A simplified version of the semantic match that finds this problem is
as follows: 
(http://www.emn.fr/x-info/coccinelle/)

// <smpl>
@def0@
expression x;
position p0;
@@
x@p0 = add_volume(...)

@protected@
expression def0.x,E;
position def0.p0;
position p;
statement S;
@@
x@p0
... when != x = E
if (!IS_ERR(x) && ...) {<... x@p ...>} else S

@unprotected@
expression def0.x,E;
identifier fld;
position def0.p0;
position p != protected.p;
@@
x@p0
... when != x = E
* x@p->fld
// </smpl>

Signed-off-by:  Julien Brunel <brunel@...u.dk>
Signed-off-by:  Julia Lawall <julia@...u.dk>

---
 drivers/mtd/ubi/scan.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff -p -u a/drivers/mtd/ubi/scan.c b/drivers/mtd/ubi/scan.c
--- a/drivers/mtd/ubi/scan.c
+++ b/drivers/mtd/ubi/scan.c
@@ -387,7 +387,7 @@ int ubi_scan_add_used(struct ubi_device 
 		pnum, vol_id, lnum, ec, sqnum, bitflips);
 
 	sv = add_volume(si, vol_id, pnum, vid_hdr);
-	if (IS_ERR(sv) < 0)
+	if (IS_ERR(sv))
 		return PTR_ERR(sv);
 
 	if (si->max_sqnum < sqnum)
--
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