scsi: libsas: fix length error in sas_smp_handler()

The return value of smp_execute_task_sg() is the untransferred residual,
but bsg_job_done() requires the length of payload received. This makes
SMP passthrough commands from userland by sg ioctl to libsas get a wrong
response. The userland tools such as smp_utils failed because of these
wrong responses:

~#smp_discover /dev/bsg/expander-2\:13
response too short, len=0
~#smp_discover /dev/bsg/expander-2\:134
response too short, len=0

Fix this by passing the actual received length to bsg_job_done(). And if
smp_execute_task_sg() returns 0, this means received length is exactly
the buffer length.

[mkp: typo]

Fixes: 651a01364994 ("scsi: scsi_transport_sas: switch to bsg-lib for SMP passthrough")
Cc: <stable@vger.kernel.org> # v4.14+
Signed-off-by: Jason Yan <yanaijie@huawei.com>
Reported-by: chenqilin <chenqilin2@huawei.com>
Tested-by: chenqilin <chenqilin2@huawei.com>
CC: Christoph Hellwig <hch@lst.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

1 files changed, 5 insertions, 5 deletions

diff --git a/drivers/scsi/libsas/sas_expander.c b/drivers/scsi/libsas/sas_expander.c
index 174e5eff6155..c7f21661b3cd 100644
--- a/drivers/scsi/libsas/sas_expander.c
+++ b/drivers/scsi/libsas/sas_expander.c
@@ -2145,7 +2145,7 @@ void sas_smp_handler(struct bsg_job *job, struct Scsi_Host *shost,
                 struct sas_rphy *rphy)
 {
         struct domain_device *dev;
-        unsigned int reslen = 0;
+        unsigned int rcvlen = 0;
         int ret = -EINVAL;
 
         /* no rphy means no smp target support (ie aic94xx host) */
@@ -2179,12 +2179,12 @@ void sas_smp_handler(struct bsg_job *job, struct Scsi_Host *shost,
 
         ret = smp_execute_task_sg(dev, job->request_payload.sg_list,
                         job->reply_payload.sg_list);
-        if (ret > 0) {
-                /* positive number is the untransferred residual */
-                reslen = ret;
+        if (ret >= 0) {
+                /* bsg_job_done() requires the length received  */
+                rcvlen = job->reply_payload.payload_len - ret;
                 ret = 0;
         }
 
 out:
-        bsg_job_done(job, ret, reslen);
+        bsg_job_done(job, ret, rcvlen);
 }