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target: Fix kref->refcount underflow in transport_cmd_finish_abort

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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@sandisk.com>
Tested-by: Bart Van Assche <bart.vanassche@sandisk.com>
Cc: Mike Christie <mchristi@redhat.com>
Cc: Hannes Reinecke <hare@suse.de>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Himanshu Madhani <himanshu.madhani@qlogic.com>
Cc: Sagi Grimberg <sagig@mellanox.com>
Cc: stable@vger.kernel.org # 3.14+
Tested-by: Gary Guo <ghg@datera.io>
Tested-by: Chu Yuan Lin <cyl@datera.io>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
This commit is contained in:
Nicholas Bellinger 2017-06-02 20:00:17 -07:00
parent 5e0cf5e6c4
commit 73d4e580cc
3 changed files with 15 additions and 12 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
drivers/target/target_core_internal.h
View File

@ -136,7 +136,7 @@ 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 *,

16
drivers/target/target_core_tmr.c
View File

@ -75,7 +75,7 @@ void core_tmr_release_req(struct se_tmr_req *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;
@ -91,7 +91,7 @@ static void core_tmr_handle_tas_abort(struct se_cmd *cmd, int tas)
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,
@ -184,8 +184,8 @@ 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: %llu\n", ref_tag);
@ -281,8 +281,8 @@ 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);
}
}
@ -380,8 +380,8 @@ 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);
}
}

9
drivers/target/target_core_transport.c
View File

@ -651,9 +651,10 @@ static void transport_lun_remove_cmd(struct se_cmd *cmd)
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);
@ -665,9 +666,11 @@ void transport_cmd_finish_abort(struct se_cmd *cmd, int remove)
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)