From: Jiang Liu <liuj97@gmail.com>
Date: Thu, 6 Jun 2013 16:07:26 +0000 (+0800)
Subject: zram: avoid access beyond the zram device
X-Git-Tag: v3.2.49~71
X-Git-Url: https://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=624d1705fa1d6e4c647ca5859ecd921748bd85bf;p=pandora-kernel.git

zram: avoid access beyond the zram device

commit 12a7ad3b810e77137d0caf97a6dd97591e075b30 upstream.

Function valid_io_request() should verify the entire request are within
the zram device address range. Otherwise it may cause invalid memory
access when accessing/modifying zram->meta->table[index] because the
'index' is out of range. Then it may access non-exist memory, randomly
modify memory belong to other subsystems, which is hard to track down.

Signed-off-by: Jiang Liu <jiang.liu@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---

diff --git a/drivers/staging/zram/zram_drv.c b/drivers/staging/zram/zram_drv.c
index 72d80607aad1..926d483139b8 100644
--- a/drivers/staging/zram/zram_drv.c
+++ b/drivers/staging/zram/zram_drv.c
@@ -541,13 +541,20 @@ out:
  */
 static inline int valid_io_request(struct zram *zram, struct bio *bio)
 {
-	if (unlikely(
-		(bio->bi_sector >= (zram->disksize >> SECTOR_SHIFT)) ||
-		(bio->bi_sector & (ZRAM_SECTOR_PER_LOGICAL_BLOCK - 1)) ||
-		(bio->bi_size & (ZRAM_LOGICAL_BLOCK_SIZE - 1)))) {
+	u64 start, end, bound;
+	
+	/* unaligned request */
+	if (unlikely(bio->bi_sector & (ZRAM_SECTOR_PER_LOGICAL_BLOCK - 1)))
+		return 0;
+	if (unlikely(bio->bi_size & (ZRAM_LOGICAL_BLOCK_SIZE - 1)))
+		return 0;
 
+	start = bio->bi_sector;
+	end = start + (bio->bi_size >> SECTOR_SHIFT);
+	bound = zram->disksize >> SECTOR_SHIFT;
+	/* out of range range */
+	if (unlikely(start >= bound || end >= bound || start > end))
 		return 0;
-	}
 
 	/* I/O request is valid */
 	return 1;