scsi: bsg: Report synchronous data copyback failures

scsi_bsg_sg_io_fn() ignores the result of blk_rq_unmap_user(). For a
data-in command that uses a bounce buffer, unmapping copies the completed
data to userspace. If that copy fails, SG_IO can report success despite the
copyback failure.

Capture the unmap status. Preserve an earlier sense-buffer copy error and
otherwise return the data copyback error. This matches the error precedence
used by scsi_complete_sghdr_rq().

On x86_64, a virtio-scsi INQUIRY with an unaligned PROT_NONE destination
made ioctl() return 0 in 20/20 runs before this change and return -1 with
errno EFAULT in 20/20 runs afterward. Writable controls succeeded in 20/20
runs on both kernels.

Fixes: 10e8855b9451 ("bsg: add SG_IO to SG v4")
Cc: stable@vger.kernel.org
Signed-off-by: Yingjie Wang <x-professor@outlook.com>
Reviewed-by: Yang Xiuwei <yangxiuwei@kylinos.cn>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Link: https://patch.msgid.link/2561d633cc8cef513d75eb1df260046a4971e783.1792772194.git.x-professor@outlook.com
Signed-off-by: Martin K. Petersen (Oracle) <mkp@kernel.org>

0 files changed, 0 insertions, 0 deletions