-----Original Message----- From: xuliqun [mailto:xuliqun@huayun.com] Sent: Thursday, September 2, 2021 2:30 PM To: chengjian (D) cj.chengjian@huawei.com Cc: Caozhi (George, Open Source) george.cao@huawei.com Subject: [PATCH kernel-4.19 2/2] virtio_blk: fix handling single range discard request

mainline inclusion from mainline-5.14-rc7 commit af822aa68fbdf0a480a17462ed70232998127453 category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/I47ITN CVE: NA

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1f23816 ("virtio_blk: add discard and write zeroes support") starts to support multi-range discard for virtio-blk. However, the virtio-blk disk may report max discard segment as 1, at least that is exactly what qemu is doing.

So far, block layer switches to normal request merge if max discard segment limit is 1, and multiple bios can be merged to single segment. This way may cause memory corruption in virtblk_setup_discard_write_zeroes().

Fix the issue by handling single max discard segment in straightforward way.

Fixes: 1f23816 ("virtio_blk: add discard and write zeroes support") Signed-off-by: Ming Lei ming.lei@redhat.com Reviewed-by: Christoph Hellwig hch@lst.de Cc: Changpeng Liu changpeng.liu@intel.com Cc: Daniel Verkamp dverkamp@chromium.org Cc: Michael S. Tsirkin mst@redhat.com Cc: Stefan Hajnoczi stefanha@redhat.com Cc: Stefano Garzarella sgarzare@redhat.com Signed-off-by: Jens Axboe axboe@kernel.dk

Signed-off-by: xuliqun xuliqun@huayun.com --- drivers/block/virtio_blk.c | 31 +++++++++++++++++++++++-------- 1 file changed, 23 insertions(+), 8 deletions(-)

diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c index 74c17692acf9..da4f2b744904 100644 --- a/drivers/block/virtio_blk.c +++ b/drivers/block/virtio_blk.c @@ -204,16 +204,31 @@ static int virtblk_setup_discard_write_zeroes(struct request *req, bool unmap) if (!range) return -ENOMEM;

- __rq_for_each_bio(bio, req) { - u64 sector = bio->bi_iter.bi_sector; - u32 num_sectors = bio->bi_iter.bi_size >> SECTOR_SHIFT; - - range[n].flags = cpu_to_le32(flags); - range[n].num_sectors = cpu_to_le32(num_sectors); - range[n].sector = cpu_to_le64(sector); - n++; + /* + * Single max discard segment means multi-range discard isn't + * supported, and block layer only runs contiguity merge like + * normal RW request. So we can't reply on bio for retrieving + * each range info. + */ + if (queue_max_discard_segments(req->q) == 1) { + range[0].flags = cpu_to_le32(flags); + range[0].num_sectors = cpu_to_le32(blk_rq_sectors(req)); + range[0].sector = cpu_to_le64(blk_rq_pos(req)); + n = 1; + } else { + __rq_for_each_bio(bio, req) { + u64 sector = bio->bi_iter.bi_sector; + u32 num_sectors = bio->bi_iter.bi_size >> SECTOR_SHIFT; + + range[n].flags = cpu_to_le32(flags); + range[n].num_sectors = cpu_to_le32(num_sectors); + range[n].sector = cpu_to_le64(sector); + n++; + } }

+ WARN_ON_ONCE(n != segments); + req->special_vec.bv_page = virt_to_page(range); req->special_vec.bv_offset = offset_in_page(range); req->special_vec.bv_len = sizeof(*range) * segments; -- 2.16.2