target: Fix ->data_length re-assignment bug with SCSI overflow
This patch fixes a long-standing bug with SCSI overflow handling
where se_cmd->data_length was incorrectly being re-assigned to
the larger CDB extracted allocation length, resulting in a number
of fabric level errors that would end up causing a session reset
in most cases. So instead now:
- Only re-assign se_cmd->data_length durining UNDERFLOW (to use the
smaller value)
- Use existing se_cmd->data_length for OVERFLOW (to use the smaller
value)
This fix has been tested with the following CDB to generate an
SCSI overflow:
sg_raw -r512 /dev/sdc 28 0 0 0 0 0 0 0 9 0
Tested using iscsi-target, tcm_qla2xxx, loopback and tcm_vhost fabric
ports. Here is a bit more detail on each case:
- iscsi-target: Bug with open-iscsi with overflow, sg_raw returns
-3584 bytes of data.
- tcm_qla2xxx: Working as expected, returnins 512 bytes of data
- loopback: sg_raw returns CHECK_CONDITION, from overflow rejection
in transport_generic_map_mem_to_cmd()
- tcm_vhost: Same as loopback
Reported-by: Roland Dreier <roland@purestorage.com>
Cc: Roland Dreier <roland@purestorage.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Boaz Harrosh <bharrosh@panasas.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
diff --git a/drivers/target/target_core_transport.c b/drivers/target/target_core_transport.c
index 4de3186dc..3425098 100644
--- a/drivers/target/target_core_transport.c
+++ b/drivers/target/target_core_transport.c
@@ -1181,15 +1181,20 @@
/* Returns CHECK_CONDITION + INVALID_CDB_FIELD */
goto out_invalid_cdb_field;
}
-
+ /*
+ * For the overflow case keep the existing fabric provided
+ * ->data_length. Otherwise for the underflow case, reset
+ * ->data_length to the smaller SCSI expected data transfer
+ * length.
+ */
if (size > cmd->data_length) {
cmd->se_cmd_flags |= SCF_OVERFLOW_BIT;
cmd->residual_count = (size - cmd->data_length);
} else {
cmd->se_cmd_flags |= SCF_UNDERFLOW_BIT;
cmd->residual_count = (cmd->data_length - size);
+ cmd->data_length = size;
}
- cmd->data_length = size;
}
return 0;