This is a note to let you know that I've just added the patch titled
target: Fix kref->refcount underflow in transport_cmd_finish_abort
to the 3.18-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-fix-kref-refcount-underflow-in-transport_cmd_finish_abort.patch
and it can be found in the queue-3.18 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 73d4e580ccc5c3e05cea002f18111f66c9c07034 Mon Sep 17 00:00:00 2001
From: Nicholas Bellinger <nab@xxxxxxxxxxxxxxx>
Date: Fri, 2 Jun 2017 20:00:17 -0700
Subject: target: Fix kref->refcount underflow in transport_cmd_finish_abort
From: Nicholas Bellinger <nab@xxxxxxxxxxxxxxx>
commit 73d4e580ccc5c3e05cea002f18111f66c9c07034 upstream.
This patch fixes a se_cmd->cmd_kref underflow during CMD_T_ABORTED
when a fabric driver drops it's second reference from below the
target_core_tmr.c based callers of transport_cmd_finish_abort().
Recently with the conversion of kref to refcount_t, this bug was
manifesting itself as:
[705519.601034] refcount_t: underflow; use-after-free.
[705519.604034] INFO: NMI handler (kgdb_nmi_handler) took too long to run: 20116.512 msecs
[705539.719111] ------------[ cut here ]------------
[705539.719117] WARNING: CPU: 3 PID: 26510 at lib/refcount.c:184 refcount_sub_and_test+0x33/0x51
Since the original kref atomic_t based kref_put() didn't check for
underflow and only invoked the final callback when zero was reached,
this bug did not manifest in practice since all se_cmd memory is
using preallocated tags.
To address this, go ahead and propigate the existing return from
transport_put_cmd() up via transport_cmd_finish_abort(), and
change transport_cmd_finish_abort() + core_tmr_handle_tas_abort()
callers to only do their local target_put_sess_cmd() if necessary.
Reported-by: Bart Van Assche <bart.vanassche@xxxxxxxxxxx>
Tested-by: Bart Van Assche <bart.vanassche@xxxxxxxxxxx>
Cc: Mike Christie <mchristi@xxxxxxxxxx>
Cc: Hannes Reinecke <hare@xxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: Himanshu Madhani <himanshu.madhani@xxxxxxxxxx>
Cc: Sagi Grimberg <sagig@xxxxxxxxxxxx>
Tested-by: Gary Guo <ghg@xxxxxxxxx>
Tested-by: Chu Yuan Lin <cyl@xxxxxxxxx>
Signed-off-by: Nicholas Bellinger <nab@xxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/target/target_core_internal.h | 2 +-
drivers/target/target_core_tmr.c | 16 ++++++++--------
drivers/target/target_core_transport.c | 9 ++++++---
3 files changed, 15 insertions(+), 12 deletions(-)
--- a/drivers/target/target_core_internal.h
+++ b/drivers/target/target_core_internal.h
@@ -92,7 +92,7 @@ int init_se_kmem_caches(void);
void release_se_kmem_caches(void);
u32 scsi_get_new_index(scsi_index_t);
void transport_subsystem_check_init(void);
-void transport_cmd_finish_abort(struct se_cmd *, int);
+int transport_cmd_finish_abort(struct se_cmd *, int);
unsigned char *transport_dump_cmd_direction(struct se_cmd *);
void transport_dump_dev_state(struct se_device *, char *, int *);
void transport_dump_dev_info(struct se_device *, struct se_lun *,
--- a/drivers/target/target_core_tmr.c
+++ b/drivers/target/target_core_tmr.c
@@ -78,7 +78,7 @@ void core_tmr_release_req(struct se_tmr_
kfree(tmr);
}
-static void core_tmr_handle_tas_abort(struct se_cmd *cmd, int tas)
+static int core_tmr_handle_tas_abort(struct se_cmd *cmd, int tas)
{
unsigned long flags;
bool remove = true, send_tas;
@@ -94,7 +94,7 @@ static void core_tmr_handle_tas_abort(st
transport_send_task_abort(cmd);
}
- transport_cmd_finish_abort(cmd, remove);
+ return transport_cmd_finish_abort(cmd, remove);
}
static int target_check_cdb_and_preempt(struct list_head *list,
@@ -190,8 +190,8 @@ void core_tmr_abort_task(
cancel_work_sync(&se_cmd->work);
transport_wait_for_tasks(se_cmd);
- transport_cmd_finish_abort(se_cmd, true);
- target_put_sess_cmd(se_cmd);
+ if (!transport_cmd_finish_abort(se_cmd, true))
+ target_put_sess_cmd(se_cmd);
printk("ABORT_TASK: Sending TMR_FUNCTION_COMPLETE for"
" ref_tag: %d\n", ref_tag);
@@ -291,8 +291,8 @@ static void core_tmr_drain_tmr_list(
cancel_work_sync(&cmd->work);
transport_wait_for_tasks(cmd);
- transport_cmd_finish_abort(cmd, 1);
- target_put_sess_cmd(cmd);
+ if (!transport_cmd_finish_abort(cmd, 1))
+ target_put_sess_cmd(cmd);
}
}
@@ -390,8 +390,8 @@ static void core_tmr_drain_state_list(
cancel_work_sync(&cmd->work);
transport_wait_for_tasks(cmd);
- core_tmr_handle_tas_abort(cmd, tas);
- target_put_sess_cmd(cmd);
+ if (!core_tmr_handle_tas_abort(cmd, tas))
+ target_put_sess_cmd(cmd);
}
}
--- a/drivers/target/target_core_transport.c
+++ b/drivers/target/target_core_transport.c
@@ -604,9 +604,10 @@ static void transport_lun_remove_cmd(str
percpu_ref_put(&lun->lun_ref);
}
-void transport_cmd_finish_abort(struct se_cmd *cmd, int remove)
+int transport_cmd_finish_abort(struct se_cmd *cmd, int remove)
{
bool ack_kref = (cmd->se_cmd_flags & SCF_ACK_KREF);
+ int ret = 0;
if (cmd->se_cmd_flags & SCF_SE_LUN_CMD)
transport_lun_remove_cmd(cmd);
@@ -618,9 +619,11 @@ void transport_cmd_finish_abort(struct s
cmd->se_tfo->aborted_task(cmd);
if (transport_cmd_check_stop_to_fabric(cmd))
- return;
+ return 1;
if (remove && ack_kref)
- transport_put_cmd(cmd);
+ ret = transport_put_cmd(cmd);
+
+ return ret;
}
static void target_complete_failure_work(struct work_struct *work)
Patches currently in stable-queue which might be from nab@xxxxxxxxxxxxxxx are
queue-3.18/target-fix-kref-refcount-underflow-in-transport_cmd_finish_abort.patch