zram: avoid access beyond the zram device

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>
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/staging/zram/zram_drv.c b/drivers/staging/zram/zram_drv.c
index f760361..9f097ce 100644 (file)
--- a/drivers/staging/zram/zram_drv.c
+++ b/drivers/staging/zram/zram_drv.c
@@ -420,13 +420,20 @@ 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;