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Commit 4a8fcc2c authored by Nicholas Bellinger's avatar Nicholas Bellinger
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[SCSI] target: Fix multi task->task_sg[] chaining logic bug 



This patch fixes a bug in transport_do_task_sg_chain() used by HW target
mode modules with sg_chain() to provide a single sg_next() walkable memory
layout for use with pci_map_sg() and friends.  This patch addresses an
issue with mapping multiple small block max_sector tasks across multiple
struct se_task->task_sg[] mappings for HW target mode operation.

This was causing OOPs with (cmd->t_task->t_tasks_no > 1) I/O traffic for
HW target drivers using transport_do_task_sg_chain(), and has been tested
so far with tcm_fc(openfcoe), tcm_qla2xxx, and ib_srpt fabrics with
t_tasks_no > 1 IBLOCK backends using a smaller max_sectors to trigger the
original issue.

Signed-off-by: default avatarNicholas Bellinger <nab@linux-iscsi.org>
Acked-by: default avatarKiran Patil <kiran.patil@intel.com>
Cc: stable@kernel.org
Signed-off-by: default avatarJames Bottomley <jbottomley@parallels.com>
parent 129257c6

drivers/target/target_core_transport.c

+15 −11
Original line number Diff line number Diff line
@@ -4776,18 +4776,20 @@ void transport_do_task_sg_chain(struct se_cmd *cmd) 
				sg_end_cur->page_link &= ~0x02;



				sg_chain(sg_head, task_sg_num, sg_head_cur);

				sg_count += (task->task_sg_num + 1);

			} else

				sg_count += task->task_sg_num;

				task_sg_num = (task->task_sg_num + 1);

			} else {

				sg_chain(sg_head, task_sg_num, sg_head_cur);

				sg_count += task->task_sg_num;

				task_sg_num = task->task_sg_num;

			}



			sg_head = sg_head_cur;

			sg_link = sg_link_cur;

			task_sg_num = task->task_sg_num;

			continue;

		}

		sg_head = sg_first = &task->task_sg[0];

		sg_link = &task->task_sg[task->task_sg_num];

		task_sg_num = task->task_sg_num;

		/*

		 * Check for single task..

		 */
@@ -4798,9 +4800,12 @@ void transport_do_task_sg_chain(struct se_cmd *cmd) 
			 */

			sg_end = &task->task_sg[task->task_sg_num - 1];

			sg_end->page_link &= ~0x02;

			sg_count += (task->task_sg_num + 1);

		} else

			sg_count += task->task_sg_num;

			task_sg_num = (task->task_sg_num + 1);

		} else {

			sg_count += task->task_sg_num;

			task_sg_num = task->task_sg_num;

		}

	}

	/*

	 * Setup the starting pointer and total t_tasks_sg_linked_no including
@@ -4809,21 +4814,20 @@ void transport_do_task_sg_chain(struct se_cmd *cmd) 
	T_TASK(cmd)->t_tasks_sg_chained = sg_first;

	T_TASK(cmd)->t_tasks_sg_chained_no = sg_count;



	DEBUG_CMD_M("Setup T_TASK(cmd)->t_tasks_sg_chained: %p and"

		" t_tasks_sg_chained_no: %u\n", T_TASK(cmd)->t_tasks_sg_chained,

	DEBUG_CMD_M("Setup cmd: %p T_TASK(cmd)->t_tasks_sg_chained: %p and"

		" t_tasks_sg_chained_no: %u\n", cmd, T_TASK(cmd)->t_tasks_sg_chained,

		T_TASK(cmd)->t_tasks_sg_chained_no);



	for_each_sg(T_TASK(cmd)->t_tasks_sg_chained, sg,

			T_TASK(cmd)->t_tasks_sg_chained_no, i) {



		DEBUG_CMD_M("SG: %p page: %p length: %d offset: %d\n",

			sg, sg_page(sg), sg->length, sg->offset);

		DEBUG_CMD_M("SG[%d]: %p page: %p length: %d offset: %d, magic: 0x%08x\n",

			i, sg, sg_page(sg), sg->length, sg->offset, sg->sg_magic);

		if (sg_is_chain(sg))

			DEBUG_CMD_M("SG: %p sg_is_chain=1\n", sg);

		if (sg_is_last(sg))

			DEBUG_CMD_M("SG: %p sg_is_last=1\n", sg);

	}



}

EXPORT_SYMBOL(transport_do_task_sg_chain);