Re: [PATCH 1/5] block: move discard checks into the ioctl handler

Keith Busch
2024-03-12T22:12:57Z

On Tue, Mar 12, 2024 at 08:45:27AM -0600, Christoph Hellwig wrote:
> @@ -95,6 +95,8 @@ static int compat_blkpg_ioctl(struct block_device *bdev,
> static int blk_ioctl_discard(struct block_device *bdev, blk_mode_t mode,
> unsigned long arg)
> {
> + sector_t bs_mask = (bdev_logical_block_size(bdev) >> SECTOR_SHIFT) - 1;
> + sector_t sector, nr_sects;
> uint64_t range[2];
> uint64_t start, len;
> struct inode *inode = bdev->bd_inode;
> @@ -105,18 +107,21 @@ static int blk_ioctl_discard(struct block_device *bdev, blk_mode_t mode,
>
> if (!bdev_max_discard_sectors(bdev))
> return -EOPNOTSUPP;
> + if (bdev_read_only(bdev))
> + return -EPERM;
>
> if (copy_from_user(range, (void __user *)arg, sizeof(range)))
> return -EFAULT;
>
> start = range[0];
> len = range[1];
> + sector = start >> SECTOR_SHIFT;
> + nr_sects = len >> SECTOR_SHIFT;
>
> - if (start & 511)
> + if (!nr_sects)
> return -EINVAL;
> - if (len & 511)
> + if ((sector | nr_sects) & bs_mask)
> return -EINVAL;
> -
> if (start + len > bdev_nr_bytes(bdev))
> return -EINVAL;

Maybe you want to shift lower bytes out of consideration, but it is
different, right? For example, if I call this ioctl with start=5 and
len=555, it would return EINVAL, but your change would let it succeed
the same as if start=0, len=512.