On Wed, 4 Apr 2018 10:53:55 -0700
"Bart Van Assche" <bart.vanassche@xxxxxxx> wrote:
> Commit e39a97353e53 modified __scsi_error_from_host_byte() such
> that that function translates DID_OK into BLK_STS_OK. However,
> the description of that commit is wrong: it mentions that commit
> 2a842acab109 introduced a bug in __scsi_error_from_host_byte()
> although that commit did not change the behavior of that function.
> Additionally, commit e39a97353e53 introduced a severe bug: it causes
> commands that fail with hostbyte=DID_OK and driverbyte=DRIVER_SENSE
> to be completed with BLK_STS_OK. Fix __scsi_error_from_host_byte()
> by only translating good status values into BLK_STS_OK.
>
> Fixes: e39a97353e53 ("scsi: core: return BLK_STS_OK for DID_OK in
> __scsi_error_from_host_byte()") Reported-by: Damien Le Moal
> <damien.lemoal@xxxxxxx> Signed-off-by: Bart Van Assche
> <bart.vanassche@xxxxxxx> Cc: Hannes Reinecke <hare@xxxxxxxx>
> Cc: Douglas Gilbert <dgilbert@xxxxxxxxxxxx>
> Cc: Damien Le Moal <damien.lemoal@xxxxxxx>
> Cc: Christoph Hellwig <hch@xxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
> ---
>
> Changes compared to v1:
> - Modified __scsi_error_from_host_byte() such that it again returns
> BLK_STS_OK for CONDITION MET and other result codes that represent
> success.
>
> drivers/scsi/scsi_lib.c | 8 +++++++-
> 1 file changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
> index 74a39db57d49..1496b34af409 100644
> --- a/drivers/scsi/scsi_lib.c
> +++ b/drivers/scsi/scsi_lib.c
> @@ -736,7 +736,13 @@ static blk_status_t
> __scsi_error_from_host_byte(struct scsi_cmnd *cmd, {
> switch (host_byte(result)) {
> case DID_OK:
> - return BLK_STS_OK;
> + /*
> + * Also check the other bytes than the status byte
> in result
> + * to handle the case when a SCSI LLD sets result to
> + * DRIVER_SENSE << 24 without setting
> SAM_STAT_CHECK_CONDITION.
> + */
> + return scsi_status_is_good(result) && (result &
> ~0xff) == 0 ?
> + BLK_STS_OK : BLK_STS_IOERR;
> case DID_TRANSPORT_FAILFAST:
> return BLK_STS_TRANSPORT;
> case DID_TARGET_FAILURE:
And a further nit-pick: the function is called
__scsi_error_from_host_byte(), so it's only logical that it would only
check the host_byte().
What's wrong is the _usage_ here; after calling
__scsi_error_from_host_byte() we need to check if the _other_ bits of
the results are non-zero to end up with a valid result.
Hence I would advocate to either rename this function
(__scsi_error_from_result() ?) or evaluate the remaining bits outside
this function.
But I would advocate for the former; otherwise the same issue will crop
up again in the future.
Cheers,
Hannes