mtd: mtdoops: limit the maximum mtd partition size

Make the maximum mtdoops partition size to be 8MiB. Indeed, it does
not make sense to use anything larger than that anyway. This limit
makes it possible to catch stupid mistakes where the user gives e.g.,
a rootfs partition to mtdoops (which will happily erase it).
Signed-off-by: Simon Kagstrom <simon.kagstrom@netinsight.net>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

drivers/mtd/mtdoops.c

@@ -33,6 +33,9 @@
 #include <linux/interrupt.h>
 #include <linux/mtd/mtd.h>
 
+/* Maximum MTD partition size */
+#define MTDOOPS_MAX_MTD_SIZE (8 * 1024 * 1024)
+
 #define MTDOOPS_KERNMSG_MAGIC 0x5d005d00
 #define OOPS_PAGE_SIZE 4096
 
@@ -310,6 +313,12 @@ static void mtdoops_notify_add(struct mtd_info *mtd)
 		return;
 	}
 
+	if (mtd->size > MTDOOPS_MAX_MTD_SIZE) {
+		printk(KERN_ERR "mtdoops: mtd%d is too large (limit is %d MiB)\n",
+		       mtd->index, MTDOOPS_MAX_MTD_SIZE / 1024 / 1024);
+		return;
+	}
+
 	/* oops_page_used is a bit field */
 	cxt->oops_page_used = vmalloc(DIV_ROUND_UP(mtdoops_pages,
 			BITS_PER_LONG));
@@ -317,14 +326,10 @@ static void mtdoops_notify_add(struct mtd_info *mtd)
 		printk(KERN_ERR "Could not allocate page array\n");
 		return;
 	}
+
 	cxt->mtd = mtd;
-	if (mtd->size > INT_MAX)
-		cxt->oops_pages = INT_MAX / OOPS_PAGE_SIZE;
-	else
 	cxt->oops_pages = (int)mtd->size / OOPS_PAGE_SIZE;
-
 	find_next_position(cxt);
-
 	printk(KERN_INFO "mtdoops: Attached to MTD device %d\n", mtd->index);
 }