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Subject[21/53] target: Reject SCSI data overflow for fabrics using transport_generic_map_mem_to_cmd
3.1-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Nicholas Bellinger <nab@linux-iscsi.org>

commit fef58a6096770ed6ab49103a430cc755254a74d9 upstream.

This patch changes transport_generic_map_mem_to_cmd() to reject SCSI data
overflow and to send exception status with CHECK_CONDITION + TCM_INVALID_CDB_FIELD
for fabrics that are passing a pre-populated struct scatterlist (eg: tcm_loop
and iscsi-target) being mapped into se_cmd->t_data_sg and se_cmd->t_data_nents.

This addresses an OOPs where transport_allocate_data_tasks() would walk
the incorrect post OVERFLOW cmd->data_length value beyond the end of
the passed scatterlist.

Cc: Christoph Hellwig <hch@lst.de>
Cc: Andy Grover <agrover@redhat.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
drivers/target/target_core_transport.c | 12 ++++++++++++
1 file changed, 12 insertions(+)

--- a/drivers/target/target_core_transport.c
+++ b/drivers/target/target_core_transport.c
@@ -3873,6 +3873,18 @@ int transport_generic_map_mem_to_cmd(

if ((cmd->se_cmd_flags & SCF_SCSI_DATA_SG_IO_CDB) ||
(cmd->se_cmd_flags & SCF_SCSI_CONTROL_SG_IO_CDB)) {
+ /*
+ * Reject SCSI data overflow with map_mem_to_cmd() as incoming
+ * scatterlists already have been set to follow what the fabric
+ * passes for the original expected data transfer length.
+ */
+ if (cmd->se_cmd_flags & SCF_OVERFLOW_BIT) {
+ pr_warn("Rejecting SCSI DATA overflow for fabric using"
+ " SCF_PASSTHROUGH_SG_TO_MEM_NOALLOC\n");
+ cmd->se_cmd_flags |= SCF_SCSI_CDB_EXCEPTION;
+ cmd->scsi_sense_reason = TCM_INVALID_CDB_FIELD;
+ return -EINVAL;
+ }

cmd->t_data_sg = sgl;
cmd->t_data_nents = sgl_count;



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