Commit 8cd79f24 authored Oct 24, 2011 by Nicholas Bellinger

tcm_loop: Add explict read buffer memset for SCF_SCSI_CONTROL_SG_IO_CDB



This patch addresses an issue with buggy userspace code sending I/O
via scsi-generic that does not explictly clear their associated read
buffers.  It adds an explict memset of the first SGL entry within
tcm_loop_new_cmd_map() for SCF_SCSI_CONTROL_SG_IO_CDB payloads that
are currently guaranteed to be a single SGL by target-core code.

This issue is a side effect of the v3.1-rc1 merge to remove the
extra memcpy between certain control CDB types using a contigious
+ cleared buffer in target-core, and performing a memcpy into the
SGL list within tcm_loop.

It was originally mainfesting itself by udev + scsi_id + scsi-generic
not properly setting up the expected /dev/disk/by-id/ symlinks because
the INQUIRY payload was containing extra bogus data preventing the
proper NAA IEEE WWN from being parsed by userspace.

Cc: Christoph Hellwig <hch@lst.de>
Cc: Andy Grover <agrover@redhat.com>
Cc: stable@kernel.org
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

parent c9abb9bb

drivers/target/loopback/tcm_loop.c

+18 −0

Original line number	Diff line number	Diff line
		@@ -174,6 +174,24 @@ static int tcm_loop_new_cmd_map(struct se_cmd *se_cmd)
		sgl_bidi = sdb->table.sgl;
		sgl_bidi_count = sdb->table.nents;
		}
		/*
		* Because some userspace code via scsi-generic do not memset their
		* associated read buffers, go ahead and do that here for type
		* SCF_SCSI_CONTROL_SG_IO_CDB. Also note that this is currently
		* guaranteed to be a single SGL for SCF_SCSI_CONTROL_SG_IO_CDB
		* by target core in transport_generic_allocate_tasks() ->
		* transport_generic_cmd_sequencer().
		*/
		if (se_cmd->se_cmd_flags & SCF_SCSI_CONTROL_SG_IO_CDB &&
		se_cmd->data_direction == DMA_FROM_DEVICE) {
		struct scatterlist *sg = scsi_sglist(sc);
		unsigned char *buf = kmap(sg_page(sg)) + sg->offset;

		if (buf != NULL) {
		memset(buf, 0, sg->length);
		kunmap(sg_page(sg));
		}
		}

		/* Tell the core about our preallocated memory */
		ret = transport_generic_map_mem_to_cmd(se_cmd, scsi_sglist(sc),