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Subject[11/85] zram: avoid access beyond the zram device
3.2.49-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Jiang Liu <liuj97@gmail.com>

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>
---
drivers/staging/zram/zram_drv.c | 17 ++++++++++++-----
1 file changed, 12 insertions(+), 5 deletions(-)

--- 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;


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