Hi!
> From: Kent Overstreet <kent.overstreet@xxxxxxxxx>
>
> [ Upstream commit 168145f617d57bf4e474901b7ffa869337a802e6 ]
>
> bio_iov_iter_get_pages() trims the IO based on the block size of the
> block device the IO will be issued to.
>
> However, bcachefs is a multi device filesystem; when we're creating the
> bio we don't yet know which block device the bio will be submitted to -
> we have to handle the alignment checks elsewhere.
>
> Thus this is needed to avoid a null ptr deref.
We are certainly not going to backport bcachefs to -stable. Please
drop.
BR,
Pavel
> +++ b/block/bio.c
> @@ -1198,7 +1198,7 @@ static int __bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter)
> struct page **pages = (struct page **)bv;
> ssize_t size, left;
> unsigned len, i = 0;
> - size_t offset, trim;
> + size_t offset;
> int ret = 0;
>
> /*
> @@ -1223,10 +1223,12 @@ static int __bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter)
>
> nr_pages = DIV_ROUND_UP(offset + size, PAGE_SIZE);
>
> - trim = size & (bdev_logical_block_size(bio->bi_bdev) - 1);
> - iov_iter_revert(iter, trim);
> + if (bio->bi_bdev) {
> + size_t trim = size & (bdev_logical_block_size(bio->bi_bdev) - 1);
> + iov_iter_revert(iter, trim);
> + size -= trim;
> + }
>
> - size -= trim;
> if (unlikely(!size)) {
> ret = -EFAULT;
> goto out;
--
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