From: Nicholas Bellinger <nab@xxxxxxxxxxxxxxx>
This patch fixes two bugs associated with transport_do_task_sg_chain()
operation where transport_allocate_data_tasks() was incorrectly setting
task_padded_sg for all tasks, and causing bogus task->task_sg_nents
assignments + OOPsen with fabrics depending upon this code. The first bit
here adds a task_sg_nents_padded check in transport_allocate_data_tasks()
to include an extra SGL vector when necessary for tasks that expect to
be linked using sg_chain().
The second change involves making transport_do_task_sg_chain() properly
account for the extra SGL vector when task->task_padded_sg is set for
the non trailing ->task_sg or single ->task_sg allocations. Note this
patch also removes the BUG_ON(!task->task_padded_sg) check within
transport_do_task_sg_chain() as we expect this to happen normally
with the updated logic in transport_allocate_data_tasks(), along with
being bogus for CONTROL_SG_IO_CDB type payloads.
So far this bugfix has been tested with tcm_qla2xxx and iblock backends
in (task_count > 1)( and (task_count == 1) operation.
Reported-by: Kiran Patil <kiran.patil@xxxxxxxxx>
Cc: Kiran Patil <kiran.patil@xxxxxxxxx>
Cc: Andy Grover <agrover@xxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Signed-off-by: Nicholas Bellinger <nab@xxxxxxxxxxxxxxx>
---
drivers/target/target_core_transport.c | 34 +++++++++++++++++++------------
1 files changed, 21 insertions(+), 13 deletions(-)
diff --git a/drivers/target/target_core_transport.c b/drivers/target/target_core_transport.c
index efac6a9..9cc49d1 100644
--- a/drivers/target/target_core_transport.c
+++ b/drivers/target/target_core_transport.c
@@ -4044,8 +4044,6 @@ void transport_do_task_sg_chain(struct se_cmd *cmd)
if (!task->task_sg)
continue;
- BUG_ON(!task->task_padded_sg);
-
if (!sg_first) {
sg_first = task->task_sg;
chained_nents = task->task_sg_nents;
@@ -4053,9 +4051,19 @@ void transport_do_task_sg_chain(struct se_cmd *cmd)
sg_chain(sg_prev, sg_prev_nents, task->task_sg);
chained_nents += task->task_sg_nents;
}
+ /*
+ * For the padded tasks, use the extra SGL vector allocated
+ * in transport_allocate_data_tasks() for the sg_prev_nents
+ * offset into sg_chain() above.. The last task of a
+ * multi-task list, or a single task will not have
+ * task->task_sg_padded set..
+ */
+ if (task->task_padded_sg)
+ sg_prev_nents = (task->task_sg_nents + 1);
+ else
+ sg_prev_nents = task->task_sg_nents;
sg_prev = task->task_sg;
- sg_prev_nents = task->task_sg_nents;
}
/*
* Setup the starting pointer and total t_tasks_sg_linked_no including
@@ -4107,7 +4115,7 @@ static int transport_allocate_data_tasks(
cmd_sg = sgl;
for (i = 0; i < task_count; i++) {
- unsigned int task_size;
+ unsigned int task_size, task_sg_nents_padded;
int count;
task = transport_generic_get_task(cmd, data_direction);
@@ -4135,24 +4143,24 @@ static int transport_allocate_data_tasks(
* Check if the fabric module driver is requesting that all
* struct se_task->task_sg[] be chained together.. If so,
* then allocate an extra padding SG entry for linking and
- * marking the end of the chained SGL.
- * Possibly over-allocate task sgl size by using cmd sgl size.
- * It's so much easier and only a waste when task_count > 1.
- * That is extremely rare.
+ * marking the end of the chained SGL for every task except
+ * the last one for (task_count > 1) operation, or skipping
+ * the extra padding for the (task_count == 1) case.
*/
- if (cmd->se_tfo->task_sg_chaining) {
- task->task_sg_nents++;
+ if (cmd->se_tfo->task_sg_chaining && (i < (task_count - 1))) {
+ task_sg_nents_padded = (task->task_sg_nents + 1);
task->task_padded_sg = 1;
- }
+ } else
+ task_sg_nents_padded = task->task_sg_nents;
task->task_sg = kmalloc(sizeof(struct scatterlist) *
- task->task_sg_nents, GFP_KERNEL);
+ task_sg_nents_padded, GFP_KERNEL);
if (!task->task_sg) {
cmd->se_dev->transport->free_task(task);
return -ENOMEM;
}
- sg_init_table(task->task_sg, task->task_sg_nents);
+ sg_init_table(task->task_sg, task_sg_nents_padded);
task_size = task->task_size;
--
1.7.6
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