pcmcia: fix read buffer overflow

If count > 0 and dev->rlen == dev->rpos and dev->proto == 0 then we read
and write dev->rbuf[-1];

Signed-off-by: Roel Kluin <roel.kluin@gmail.com>
Cc: Harald Welte <laforge@gnumonks.org>
Cc: Dominik Brodowski <linux@dominikbrodowski.net>
Cc: Greg KH <greg@kroah.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/drivers/char/pcmcia/cm4000_cs.c b/drivers/char/pcmcia/cm4000_cs.c
index 881934c068c84e1c3599b5581a65bc7dca8d1ebf..c250a31efa537c1f15ab8466b20bcc779ba214f3 100644 (file)
--- a/drivers/char/pcmcia/cm4000_cs.c
+++ b/drivers/char/pcmcia/cm4000_cs.c
@@ -1017,7 +1017,7 @@ static ssize_t cmm_read(struct file *filp, __user char *buf, size_t count,
                }
        }
 
-       if (dev->proto == 0 && count > dev->rlen - dev->rpos) {
+       if (dev->proto == 0 && count > dev->rlen - dev->rpos && i) {
                DEBUGP(4, dev, "T=0 and count > buffer\n");
                dev->rbuf[i] = dev->rbuf[i - 1];
                dev->rbuf[i - 1] = dev->procbyte;