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From: Jesper Juhl <>
To: Artem Bityutskiy <>
	David Woodhouse <>,
	Linux Kernel Mailing List <>,
	Jesper Juhl <>
Subject: [PATCH] UBI: Don't use signed int as array index before testing if it is negative
Date: Sat, 4 Aug 2007 01:25:26 +0200	[thread overview]
Message-ID: <> (raw)


I can't find anything guaranteeing that 'ubi_num' cannot be <0 in 
drivers/mtd/ubi/kapi.c::ubi_open_volume(), and in fact the code 
even tests for that and errors out if so. Unfortunately the test 
for "ubi_num < 0" happens after we've already used 'ubi_num' as 
an array index - bad thing to do if it is negative.
This patch moves the test earlier in the function and then moves 
the indexing using that variable after the check. A bit safer :-) 

Signed-off-by: Jesper Juhl <>

 drivers/mtd/ubi/kapi.c |    9 +++++++--
 1 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/mtd/ubi/kapi.c b/drivers/mtd/ubi/kapi.c
index 4a458e8..5130e54 100644
--- a/drivers/mtd/ubi/kapi.c
+++ b/drivers/mtd/ubi/kapi.c
@@ -99,16 +99,21 @@ struct ubi_volume_desc *ubi_open_volume(int ubi_num, int vol_id, int mode)
 	int err;
 	struct ubi_volume_desc *desc;
-	struct ubi_device *ubi = ubi_devices[ubi_num];
+	struct ubi_device *ubi;
 	struct ubi_volume *vol;
 	dbg_msg("open device %d volume %d, mode %d", ubi_num, vol_id, mode);
 	err = -ENODEV;
+	if (ubi_num < 0)
+		return ERR_PTR(err);
+	ubi = ubi_devices[ubi_num];
 	if (!try_module_get(THIS_MODULE))
 		return ERR_PTR(err);
-	if (ubi_num < 0 || ubi_num >= UBI_MAX_DEVICES || !ubi)
+	if (ubi_num >= UBI_MAX_DEVICES || !ubi)
 		goto out_put;
 	err = -EINVAL;

             reply	other threads:[~2007-08-03 23:27 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-08-03 23:25 Jesper Juhl [this message]
2007-08-04  9:16 ` Artem Bityutskiy

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