This is a note to let you know that I've just added the patch titled
target: Avoid early CMD_T_PRE_EXECUTE failures during ABORT_TASK
to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
target-avoid-early-cmd_t_pre_execute-failures-during-abort_task.patch
and it can be found in the queue-4.9 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 1c21a48055a67ceb693e9c2587824a8de60a217c Mon Sep 17 00:00:00 2001
From: Nicholas Bellinger <nab@xxxxxxxxxxxxxxx>
Date: Fri, 27 Oct 2017 22:19:26 -0800
Subject: target: Avoid early CMD_T_PRE_EXECUTE failures during ABORT_TASK
From: Nicholas Bellinger <nab@xxxxxxxxxxxxxxx>
commit 1c21a48055a67ceb693e9c2587824a8de60a217c upstream.
This patch fixes bug where early se_cmd exceptions that occur
before backend execution can result in use-after-free if/when
a subsequent ABORT_TASK occurs for the same tag.
Since an early se_cmd exception will have had se_cmd added to
se_session->sess_cmd_list via target_get_sess_cmd(), it will
not have CMD_T_COMPLETE set by the usual target_complete_cmd()
backend completion path.
This causes a subsequent ABORT_TASK + __target_check_io_state()
to signal ABORT_TASK should proceed. As core_tmr_abort_task()
executes, it will bring the outstanding se_cmd->cmd_kref count
down to zero releasing se_cmd, after se_cmd has already been
queued with error status into fabric driver response path code.
To address this bug, introduce a CMD_T_PRE_EXECUTE bit that is
set at target_get_sess_cmd() time, and cleared immediately before
backend driver dispatch in target_execute_cmd() once CMD_T_ACTIVE
is set.
Then, check CMD_T_PRE_EXECUTE within __target_check_io_state() to
determine when an early exception has occured, and avoid aborting
this se_cmd since it will have already been queued into fabric
driver response path code.
Reported-by: Donald White <dew@xxxxxxxxx>
Cc: Donald White <dew@xxxxxxxxx>
Cc: Mike Christie <mchristi@xxxxxxxxxx>
Cc: Hannes Reinecke <hare@xxxxxxxx>
Signed-off-by: Nicholas Bellinger <nab@xxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/target/target_core_tmr.c | 9 +++++++++
drivers/target/target_core_transport.c | 2 ++
include/target/target_core_base.h | 1 +
3 files changed, 12 insertions(+)
--- a/drivers/target/target_core_tmr.c
+++ b/drivers/target/target_core_tmr.c
@@ -133,6 +133,15 @@ static bool __target_check_io_state(stru
spin_unlock(&se_cmd->t_state_lock);
return false;
}
+ if (se_cmd->transport_state & CMD_T_PRE_EXECUTE) {
+ if (se_cmd->scsi_status) {
+ pr_debug("Attempted to abort io tag: %llu early failure"
+ " status: 0x%02x\n", se_cmd->tag,
+ se_cmd->scsi_status);
+ spin_unlock(&se_cmd->t_state_lock);
+ return false;
+ }
+ }
if (sess->sess_tearing_down || se_cmd->cmd_wait_set) {
pr_debug("Attempted to abort io tag: %llu already shutdown,"
" skipping\n", se_cmd->tag);
--- a/drivers/target/target_core_transport.c
+++ b/drivers/target/target_core_transport.c
@@ -1939,6 +1939,7 @@ void target_execute_cmd(struct se_cmd *c
}
cmd->t_state = TRANSPORT_PROCESSING;
+ cmd->transport_state &= ~CMD_T_PRE_EXECUTE;
cmd->transport_state |= CMD_T_ACTIVE|CMD_T_BUSY|CMD_T_SENT;
spin_unlock_irq(&cmd->t_state_lock);
@@ -2592,6 +2593,7 @@ int target_get_sess_cmd(struct se_cmd *s
ret = -ESHUTDOWN;
goto out;
}
+ se_cmd->transport_state |= CMD_T_PRE_EXECUTE;
list_add_tail(&se_cmd->se_cmd_list, &se_sess->sess_cmd_list);
out:
spin_unlock_irqrestore(&se_sess->sess_cmd_lock, flags);
--- a/include/target/target_core_base.h
+++ b/include/target/target_core_base.h
@@ -493,6 +493,7 @@ struct se_cmd {
#define CMD_T_BUSY (1 << 9)
#define CMD_T_TAS (1 << 10)
#define CMD_T_FABRIC_STOP (1 << 11)
+#define CMD_T_PRE_EXECUTE (1 << 12)
spinlock_t t_state_lock;
struct kref cmd_kref;
struct completion t_transport_stop_comp;
Patches currently in stable-queue which might be from nab@xxxxxxxxxxxxxxx are
queue-4.9/iscsi-target-make-task_reassign-use-proper-se_cmd-cmd_kref.patch
queue-4.9/target-avoid-early-cmd_t_pre_execute-failures-during-abort_task.patch