dm-unstriped: cast an operand to sector_t to prevent potential uint32_t overflow

This was found by a static analyzer.
There may be a potential integer overflow issue in
unstripe_ctr(). uc->unstripe_offset and uc->unstripe_width are
defined as "sector_t"(uint64_t), while uc->unstripe,
uc->chunk_size and uc->stripes are all defined as "uint32_t".
The result of the calculation will be limited to "uint32_t"
without correct casting.
So, we recommend adding an extra cast to prevent potential
integer overflow.

Fixes: 18a5bf2 ("dm: add unstriped target")
Signed-off-by: Zichen Xie <[email protected]>
Signed-off-by: Mikulas Patocka <[email protected]>
Cc: [email protected]

Author: Gax-c

drivers/md/dm-unstripe.c

@@ -85,8 +85,8 @@ static int unstripe_ctr(struct dm_target *ti, unsigned int argc, char **argv)
 	}
 	uc->physical_start = start;
 
-	uc->unstripe_offset = uc->unstripe * uc->chunk_size;
-	uc->unstripe_width = (uc->stripes - 1) * uc->chunk_size;
+	uc->unstripe_offset = (sector_t)uc->unstripe * uc->chunk_size;
+	uc->unstripe_width = (sector_t)(uc->stripes - 1) * uc->chunk_size;
 	uc->chunk_shift = is_power_of_2(uc->chunk_size) ? fls(uc->chunk_size) - 1 : 0;
 
 	tmp_len = ti->len;