mtd: fix oops in dataflash driver

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@linux.intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/mtd/mtdchar.c b/drivers/mtd/mtdchar.c
index 50c6a1e7f675cea884a5a0bbb71fb061bfdfe932..853744d2c64613fd2aa90486e048acd65c9c155c 100644 (file)
--- 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;
 
        switch (mode) {