[ 20/47] mtd: fix oops in dataflash driver

[Greg KH]

3.3-stable review patch.  If anyone has any objections, please let me know.

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

From: Will Newton <will.newton@xxxxxxxxx>

commit 7a84477c4acebf6299b6a8bd6a1d5894eb838ffa upstream.

I'm seeing an oops in mtd_dataflash.c with Linux 3.3. What appears to
be happening is that otp_select_filemode calls mtd_read_fact_prot_reg
with -1 for offset and length and a NULL buffer to test if OTP
operations are supported. This finds its way down to otp_read in
mtd_dataflash.c and causes an oops when memcpying the returned data
into the NULL buf.

None of the checks in otp_read catches the negative length and offset.
Changing the length of the dummy read to 0 prevents the oops.

Signed-off-by: Artem Bityutskiy <artem.bityutskiy@xxxxxxxxxxxxxxx>
Signed-off-by: David Woodhouse <David.Woodhouse@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

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

--- a/drivers/mtd/mtdchar.c
+++ b/drivers/mtd/mtdchar.c
@@ -369,7 +369,7 @@ static int otp_select_filemode(struct mt
 	 * Make a fake call to mtd_read_fact_prot_reg() to check if OTP
 	 * operations are supported.
 	 */
-	if (mtd_read_fact_prot_reg(mtd, -1, -1, &retlen, NULL) == -EOPNOTSUPP)
+	if (mtd_read_fact_prot_reg(mtd, -1, 0, &retlen, NULL) == -EOPNOTSUPP)
 		return -EOPNOTSUPP;
 
 	switch (mode) {


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