[PATCH 023/270] target: support zero allocation length in INQUIRY

[Herton Ronaldo Krzesinski]

3.5.7u1 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Paolo Bonzini <pbonzini at redhat.com>

commit ffe7b0e9326d9c68f5688bef691dd49f1e0d3651 upstream.

INQUIRY processing already uses an on-heap bounce buffer for loopback,
but not for other fabrics.  Switch this to a cheaper on-stack bounce
buffer, similar to the one used by MODE SENSE and REQUEST SENSE, and
use it unconditionally.  With this in place, zero allocation length is
handled simply by checking the return address of transport_kmap_data_sg.

Testcase: sg_raw /dev/sdb 12 00 83 00 00 00
    should fail with ILLEGAL REQUEST / INVALID FIELD IN CDB sense
    does not fail without the patch
    fails correctly with the series

Signed-off-by: Paolo Bonzini <pbonzini at redhat.com>
Signed-off-by: Nicholas Bellinger <nab at linux-iscsi.org>
[ herton: code to be patched is in target_core_cdb.c on 3.5 ]
Signed-off-by: Herton Ronaldo Krzesinski <herton.krzesinski at canonical.com>
---
 drivers/target/target_core_cdb.c |   31 ++++++-------------------------
 1 file changed, 6 insertions(+), 25 deletions(-)

diff --git a/drivers/target/target_core_cdb.c b/drivers/target/target_core_cdb.c
index bf7d38a..5b20579 100644
--- a/drivers/target/target_core_cdb.c
+++ b/drivers/target/target_core_cdb.c
@@ -605,30 +605,11 @@ int target_emulate_inquiry(struct se_cmd *cmd)
 {
 	struct se_device *dev = cmd->se_dev;
 	struct se_portal_group *tpg = cmd->se_lun->lun_sep->sep_tpg;
-	unsigned char *buf, *map_buf;
+	unsigned char *rbuf;
 	unsigned char *cdb = cmd->t_task_cdb;
+	unsigned char buf[SE_INQUIRY_BUF];
 	int p, ret;
 
-	map_buf = transport_kmap_data_sg(cmd);
-	/*
-	 * If SCF_PASSTHROUGH_SG_TO_MEM_NOALLOC is not set, then we
-	 * know we actually allocated a full page.  Otherwise, if the
-	 * data buffer is too small, allocate a temporary buffer so we
-	 * don't have to worry about overruns in all our INQUIRY
-	 * emulation handling.
-	 */
-	if (cmd->data_length < SE_INQUIRY_BUF &&
-	    (cmd->se_cmd_flags & SCF_PASSTHROUGH_SG_TO_MEM_NOALLOC)) {
-		buf = kzalloc(SE_INQUIRY_BUF, GFP_KERNEL);
-		if (!buf) {
-			transport_kunmap_data_sg(cmd);
-			cmd->scsi_sense_reason = TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
-			return -ENOMEM;
-		}
-	} else {
-		buf = map_buf;
-	}
-
 	if (dev == tpg->tpg_virt_lun0.lun_se_dev)
 		buf[0] = 0x3f; /* Not connected */
 	else
@@ -660,11 +641,11 @@ int target_emulate_inquiry(struct se_cmd *cmd)
 	ret = -EINVAL;
 
 out:
-	if (buf != map_buf) {
-		memcpy(map_buf, buf, cmd->data_length);
-		kfree(buf);
+	rbuf = transport_kmap_data_sg(cmd);
+	if (rbuf) {
+		memcpy(rbuf, buf, min_t(u32, sizeof(buf), cmd->data_length));
+		transport_kunmap_data_sg(cmd);
 	}
-	transport_kunmap_data_sg(cmd);
 
 	if (!ret)
 		target_complete_cmd(cmd, GOOD);
-- 
1.7.9.5