From 8cd79f24350826b81e16990d9e12bc878e67d385 Mon Sep 17 00:00:00 2001 From: Nicholas Bellinger Date: Mon, 24 Oct 2011 13:35:37 -0700 Subject: [PATCH] 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 Cc: Andy Grover Cc: stable@kernel.org Signed-off-by: Nicholas Bellinger --- drivers/target/loopback/tcm_loop.c | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) diff --git a/drivers/target/loopback/tcm_loop.c b/drivers/target/loopback/tcm_loop.c index b15d8cbf630b..3c9c318f66ed 100644 --- a/drivers/target/loopback/tcm_loop.c +++ b/drivers/target/loopback/tcm_loop.c @@ -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), -- 2.39.5