From patchwork Fri Mar 30 10:51:02 2012
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Subject: Oops with mtd_dataflash driver in 3.3
Date: Fri, 30 Mar 2012 00:51:02 -0000
From: Will Newton <will.newton@gmail.com>
X-Patchwork-Id: 149612
Message-Id: <CAFbHwiTfaXOFX-WYWeyisK4WCiXBRv_LpEcoR=v8qvsLAO7FJQ@mail.gmail.com>
To: linux-mtd@lists.infradead.org
Cc: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>

Hi all,

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, but I'm
not sure if it is the preferred solution. Would this change be
acceptable?

        switch (mode) {

Thanks,


diff --git a/drivers/mtd/mtdchar.c b/drivers/mtd/mtdchar.c
index 50c6a1e..853744d 100644
--- a/drivers/mtd/mtdchar.c
+++ b/drivers/mtd/mtdchar.c
@@ -369,7 +369,7 @@ static int otp_select_filemode(struct
mtd_file_info *mfi, int mode)
         * 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;