[PATCH v2] Fix DID_OK handling in __scsi_error_from_host_byte()

[PATCH v2] Fix DID_OK handling in __scsi_error_from_host_byte()

[Bart Van Assche]

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@wdc.com>
Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com>
Cc: Hannes Reinecke <hare@suse.com>
Cc: Douglas Gilbert <dgilbert@interlog.com>
Cc: Damien Le Moal <damien.lemoal@wdc.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: stable@vger.kernel.org
---

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:
-- 
2.16.2

Re: [PATCH v2] Fix DID_OK handling in __scsi_error_from_host_byte()

[Douglas Gilbert]

On 2018-04-04 01:53 PM, Bart Van Assche 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@wdc.com>
> Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com>
> Cc: Hannes Reinecke <hare@suse.com>
> Cc: Douglas Gilbert <dgilbert@interlog.com>

Reviewed-by: Douglas Gilbert <dgilbert@interlog.com>

> Cc: Damien Le Moal <damien.lemoal@wdc.com>
> Cc: Christoph Hellwig <hch@lst.de>
> Cc: stable@vger.kernel.org
> ---

There is some urgency here as the faulty patch is in lk 4.16.0
release.

My patch was prepared independently of seeing this one. Both
do the job (mine has a redundant status_byte(result) in the
conditional). And the function name is now completely misleading
but due to the urgency, that can wait for another day.

> 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:
> 

Re: [PATCH v2] Fix DID_OK handling in __scsi_error_from_host_byte()

[Lee Duncan]

On 04/04/2018 10:53 AM, Bart Van Assche 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@wdc.com>
> Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com>
> Cc: Hannes Reinecke <hare@suse.com>
> Cc: Douglas Gilbert <dgilbert@interlog.com>
> Cc: Damien Le Moal <damien.lemoal@wdc.com>
> Cc: Christoph Hellwig <hch@lst.de>
> Cc: stable@vger.kernel.org
> ---
> 
> 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:
> 

Reviewed-by: Lee Duncan <lduncan@suse.com>

Re: [PATCH v2] Fix DID_OK handling in __scsi_error_from_host_byte()

[Damien Le Moal]

On Wed, 2018-04-04 at 10:53 -0700, Bart Van Assche 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@wdc.com>
> Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com>
> Cc: Hannes Reinecke <hare@suse.com>
> Cc: Douglas Gilbert <dgilbert@interlog.com>
> Cc: Damien Le Moal <damien.lemoal@wdc.com>
> Cc: Christoph Hellwig <hch@lst.de>
> Cc: stable@vger.kernel.org
> ---
> 
> 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;

This fixes the problem on my system.

Tested-by: Damien Le Moal <damien.lemoal@wdc.com>

-- 
Damien Le Moal
Western Digital

Re: [PATCH v2] Fix DID_OK handling in __scsi_error_from_host_byte()

[Hannes Reinecke]

On Wed,  4 Apr 2018 10:53:55 -0700
"Bart Van Assche" <bart.vanassche@wdc.com> 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@wdc.com> Signed-off-by: Bart Van Assche
> <bart.vanassche@wdc.com> Cc: Hannes Reinecke <hare@suse.com>
> Cc: Douglas Gilbert <dgilbert@interlog.com>
> Cc: Damien Le Moal <damien.lemoal@wdc.com>
> Cc: Christoph Hellwig <hch@lst.de>
> Cc: stable@vger.kernel.org
> ---
> 
> 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

Re: [PATCH v2] Fix DID_OK handling in __scsi_error_from_host_byte()

[Christoph Hellwig]

On Wed, Apr 04, 2018 at 10:53:55AM -0700, Bart Van Assche wrote:
> +		/*
> +		 * 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;

How about an readable version of the statement above?

		if (scsi_status_is_good(result) && (result & ~0xff))
			return BLK_STS_OK;
		return BLK_STS_IOERR;

Re: [PATCH v2] Fix DID_OK handling in __scsi_error_from_host_byte()

[Christoph Hellwig]

On Thu, Apr 05, 2018 at 08:43:18AM +0200, Hannes Reinecke wrote:
> 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.

Please also drop the pointless double underscore prefix while at it,
otherwise fully agreed.