[PATCH] target: fix crash in cmd tracing when cmd didn't match a LUN

Spencer Baugh
2015-07-21T22:08:24Z

From: Alexei Potashnik <alexei@purestorage.com>

If command didn't match a LUN and we're sending check condition, the
target_cmd_complete ftrace point will crash because it assumes that
cmd->t_task_cdb has been set.

The fix will temporarily set t_task_cdb to the se_cmd buffer
and copy first 6 bytes of cdb in there as soon as possible.
At a later point t_task_cdb is reset to the correct buffer,
but until then traces and printks don't cause a crash.

Signed-off-by: Alexei Potashnik <alexei@purestorage.com>
Signed-off-by: Spencer Baugh <sbaugh@catern.com>
---
drivers/target/target_core_device.c | 7 +++++++
drivers/target/target_core_transport.c | 7 ++++---
2 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/drivers/target/target_core_device.c b/drivers/target/target_core_device.c
index c4a8db6..b74dfb2 100644
--- a/drivers/target/target_core_device.c
+++ b/drivers/target/target_core_device.c
@@ -63,6 +63,13 @@ transport_lookup_cmd_lun(struct se_cmd *se_cmd, u64 unpacked_lun)
struct se_node_acl *nacl = se_sess->se_node_acl;
struct se_dev_entry *deve;

+ /* Temporarily set t_task_cdb to the se_cmd buffer and save a portion
+ * of cdb in there (fabrics must provide at least 6 bytes). t_task_cdb
+ * will be correctly replaced in target_setup_cmd_from_cdb. Until then
+ * tracing and printks can access t_task_cdb without causing a crash. */
+ se_cmd->t_task_cdb = se_cmd->__t_task_cdb;
+ memcpy(se_cmd->t_task_cdb, cdb, 6);
+
rcu_read_lock();
deve = target_nacl_find_deve(nacl, unpacked_lun);
if (deve) {
diff --git a/drivers/target/target_core_transport.c b/drivers/target/target_core_transport.c
index ce8574b..8dd15c7 100644
--- a/drivers/target/target_core_transport.c
+++ b/drivers/target/target_core_transport.c
@@ -1210,15 +1210,16 @@ target_setup_cmd_from_cdb(struct se_cmd *cmd, unsigned char *cdb)
* setup the pointer from __t_task_cdb to t_task_cdb.
*/
if (scsi_command_size(cdb) > sizeof(cmd->__t_task_cdb)) {
- cmd->t_task_cdb = kzalloc(scsi_command_size(cdb),
- GFP_KERNEL);
- if (!cmd->t_task_cdb) {
+ unsigned char *ptr = kzalloc(scsi_command_size(cdb),
+ GFP_KERNEL);
+ if (!ptr) {
pr_err("Unable to allocate cmd->t_task_cdb"
" %u > sizeof(cmd->__t_task_cdb): %lu ops\n",
scsi_command_size(cdb),
(unsigned long)sizeof(cmd->__t_task_cdb));
return TCM_OUT_OF_RESOURCES;
}
+ cmd->t_task_cdb = ptr;
} else
cmd->t_task_cdb = &cmd->__t_task_cdb[0];
/*
--
2.4.3