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Commit 3717ef0c authored by Paolo Bonzini's avatar Paolo Bonzini Committed by Nicholas Bellinger
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target: support zero-size allocation lengths in transport_kmap_data_sg 



In order to support zero-size allocation lengths, do not assert
that we have a scatterlist until after checking cmd->data_length.

But once we do this, we can have two cases of transport_kmap_data_sg
returning NULL: a zero-size allocation length, or an out-of-memory
condition.  Report the latter using sense codes, so that the SCSI
command that triggered it will fail.

Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: default avatarNicholas Bellinger <nab@linux-iscsi.org>
parent 9b16b9ed

drivers/target/target_core_transport.c

+9 −4
Original line number Diff line number Diff line
@@ -2190,7 +2190,6 @@ void *transport_kmap_data_sg(struct se_cmd *cmd) 
	struct page **pages;

	int i;



	BUG_ON(!sg);

	/*

	 * We need to take into account a possible offset here for fabrics like

	 * tcm_loop who may be using a contig buffer from the SCSI midlayer for
@@ -2198,13 +2197,17 @@ void *transport_kmap_data_sg(struct se_cmd *cmd) 
	 */

	if (!cmd->t_data_nents)

		return NULL;

	else if (cmd->t_data_nents == 1)



	BUG_ON(!sg);

	if (cmd->t_data_nents == 1)

		return kmap(sg_page(sg)) + sg->offset;



	/* >1 page. use vmap */

	pages = kmalloc(sizeof(*pages) * cmd->t_data_nents, GFP_KERNEL);

	if (!pages)

	if (!pages) {

		cmd->scsi_sense_reason = TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;

		return NULL;

	}



	/* convert sg[] to pages[] */

	for_each_sg(cmd->t_data_sg, sg, cmd->t_data_nents, i) {
@@ -2213,8 +2216,10 @@ void *transport_kmap_data_sg(struct se_cmd *cmd) 


	cmd->t_data_vmap = vmap(pages, cmd->t_data_nents,  VM_MAP, PAGE_KERNEL);

	kfree(pages);

	if (!cmd->t_data_vmap)

	if (!cmd->t_data_vmap) {

		cmd->scsi_sense_reason = TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;

		return NULL;

	}



	return cmd->t_data_vmap + cmd->t_data_sg[0].offset;

}