[PATCH] block: reject polled dio with user integrity metadata

[PATCH] block: reject polled dio with user integrity metadata

[Yang Xiuwei]

IOCB_HAS_METADATA leaves iocb->private as a uio_meta, while
iocb_bio_iopoll() expects a bio. Since 2729a60bbfb9, metadata I/O
always uses __blkdev_direct_IO(), which never publishes the bio for
polling, so IOPOLL calls bio_poll() on the uio_meta.

Reproducer: io_uring IOPOLL plus a PI attribute on an integrity device
(scsi_debug dif=1 dix=1). KASAN reports:

  Oops: general protection fault, probably for non-canonical
  address 0xdffffc0000000004
  KASAN: null-ptr-deref in range
  [0x0000000000000020-0x0000000000000027]
  RIP: 0010:bio_poll+0x9d/0x4b0
  Call Trace:
   iocb_bio_iopoll+0x5b/0x80
   io_uring_classic_poll+0xf3/0x140
   io_do_iopoll+0x4e3/0xc00
   io_iopoll_check+0x275/0x560
   __do_sys_io_uring_enter+0x2e5/0x720

Return -EOPNOTSUPP when HIPRI is combined with user metadata.

Fixes: 2729a60bbfb9 ("block: don't silently ignore metadata for sync read/write")
Assisted-by: LLM
Signed-off-by: Yang Xiuwei <yangxiuwei@kylinos.cn>
---
 block/fops.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/block/fops.c b/block/fops.c
index 2ce7c6c4714e..c915ec0126d7 100644
--- a/block/fops.c
+++ b/block/fops.c
@@ -402,6 +402,11 @@ static ssize_t blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
 	if (blkdev_dio_invalid(bdev, iocb, iter))
 		return -EINVAL;
 
+	/* HIPRI needs private as bio; HAS_METADATA keeps it as uio_meta */
+	if ((iocb->ki_flags & IOCB_HIPRI) &&
+	    (iocb->ki_flags & IOCB_HAS_METADATA))
+		return -EOPNOTSUPP;
+
 	if (iov_iter_rw(iter) == WRITE) {
 		u16 max_write_streams = bdev_max_write_streams(bdev);
 
-- 
2.25.1

Re: [PATCH] block: reject polled dio with user integrity metadata

[Jens Axboe]

On Wed, 23 Sep 2026 17:37:32 +0800, Yang Xiuwei wrote:
> IOCB_HAS_METADATA leaves iocb->private as a uio_meta, while
> iocb_bio_iopoll() expects a bio. Since 2729a60bbfb9, metadata I/O
> always uses __blkdev_direct_IO(), which never publishes the bio for
> polling, so IOPOLL calls bio_poll() on the uio_meta.
> 
> Reproducer: io_uring IOPOLL plus a PI attribute on an integrity device
> (scsi_debug dif=1 dix=1). KASAN reports:
> 
> [...]

Applied, thanks!

[1/1] block: reject polled dio with user integrity metadata
      commit: 2a42e6fe1293f2e2d579c9fe5bbab056dd8b880e

Best regards,
-- 
Jens Axboe

Re: [PATCH] block: reject polled dio with user integrity metadata

[Christoph Hellwig]

On Wed, Sep 23, 2026 at 05:37:32PM +0800, Yang Xiuwei wrote:
> IOCB_HAS_METADATA leaves iocb->private as a uio_meta, while
> iocb_bio_iopoll() expects a bio. Since 2729a60bbfb9, metadata I/O
> always uses __blkdev_direct_IO(), which never publishes the bio for
> polling, so IOPOLL calls bio_poll() on the uio_meta.
> 
> Reproducer: io_uring IOPOLL plus a PI attribute on an integrity device
> (scsi_debug dif=1 dix=1). KASAN reports:

Can you add a reproducer for this to blktests?

Re: [PATCH] block: reject polled dio with user integrity metadata

[Yang Xiuwei]

Hi Christoph,

On Wed, Sep 23, 2026 at 04:39:37PM +0200, Christoph Hellwig wrote:
> Can you add a reproducer for this to blktests?

Yes. I'll send one that expects -EOPNOTSUPP.

Thanks,
Yang Xiuwei