Re: [PATCH -next] block: Fix the partition start may overflow in add_partition()

[zhongjinghua <zhongjinghua@huawei.com>]

在 2023/5/25 16:55, Christoph Hellwig 写道:
> On Mon, May 22, 2023 at 03:06:15PM +0800, Zhong Jinghua wrote:
>> +	if (p.start < 0 || p.length <= 0 || p.start + p.length < 0)
>> +		return -EINVAL;
>> +
>>   	start = p.start >> SECTOR_SHIFT;
>>   	length = p.length >> SECTOR_SHIFT;
>>   
>> +	/* length may be equal to 0 after right shift */
>> +	if (!length || start + length > get_capacity(bdev->bd_disk))
>> +		return -EINVAL;
> While we're at it, shouldn't these be switched to use
> check_add_overflow?

However, using check_add_overflow requires the introduction of an 
additional local variable for the third parameter, which does not make 
much difference to the current check. Is it worth it?

e.g:

diff --git a/block/ioctl.c b/block/ioctl.c
index 3223ea862523..9a40e8f864cb 100644
--- a/block/ioctl.c
+++ b/block/ioctl.c
@@ -18,7 +18,7 @@ static int blkpg_do_ioctl(struct block_device *bdev,
  {
         struct gendisk *disk = bdev->bd_disk;
         struct blkpg_partition p;
-       long long start, length;
+       long long start, length, tmp_check;

         if (!capable(CAP_SYS_ADMIN))
                 return -EACCES;
@@ -33,7 +33,7 @@ static int blkpg_do_ioctl(struct block_device *bdev,
         if (op == BLKPG_DEL_PARTITION)
                 return bdev_del_partition(disk, p.pno);

-       if (p.start < 0 || p.length <= 0 || p.start + p.length < 0)
+       if (p.start < 0 || p.length <= 0 || check_add_overflow(p.start, 
p.length, &tmp_check))
                 return -EINVAL;

         start = p.start >> SECTOR_SHIFT;

Or do you have a better idea?