[MTD] slram: Handle negative devlength correctly

A negative devlength won't get noticed and clean up:

Signed-off-by: Roel Kluin <roel.kluin@gmail.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

1 files changed, 10 insertions, 4 deletions

diff --git a/drivers/mtd/devices/slram.c b/drivers/mtd/devices/slram.c
index a425d09f35a0..00248e81ecd5 100644
--- a/drivers/mtd/devices/slram.c
+++ b/drivers/mtd/devices/slram.c
@@ -267,22 +267,28 @@ static int parse_cmdline(char *devname, char *szstart, char *szlength)
         if (*(szlength) != '+') {
                 devlength = simple_strtoul(szlength, &buffer, 0);
                 devlength = handle_unit(devlength, buffer) - devstart;
+                if (devlength < devstart)
+                        goto err_out;
+
+                devlength -= devstart;
         } else {
                 devlength = simple_strtoul(szlength + 1, &buffer, 0);
                 devlength = handle_unit(devlength, buffer);
         }
         T("slram: devname=%s, devstart=0x%lx, devlength=0x%lx\n",
                         devname, devstart, devlength);
-        if ((devstart < 0) || (devlength < 0) || (devlength % SLRAM_BLK_SZ != 0)) {
-                E("slram: Illegal start / length parameter.\n");
-                return(-EINVAL);
-        }
+        if (devlength % SLRAM_BLK_SZ != 0)
+                goto err_out;
 
         if ((devstart = register_device(devname, devstart, devlength))){
                 unregister_devices();
                 return((int)devstart);
         }
         return(0);
+
+err_out:
+        E("slram: Illegal length parameter.\n");
+        return(-EINVAL);
 }
 
 #ifndef MODULE