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target: Avoid early CMD_T_PRE_EXECUTE failures during ABORT_TASK

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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@datera.io>
Cc: Donald White <dew@datera.io>
Cc: Mike Christie <mchristi@redhat.com>
Cc: Hannes Reinecke <hare@suse.com>
Cc: stable@vger.kernel.org # 3.14+
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
This commit is contained in:
Nicholas Bellinger 2017-10-27 22:19:26 -08:00
parent 9574a497df
commit 1c21a48055
3 changed files with 12 additions and 0 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

9
drivers/target/target_core_tmr.c
View file

@ -133,6 +133,15 @@ static bool __target_check_io_state(struct se_cmd *se_cmd,
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);

2
drivers/target/target_core_transport.c
View file

@ -1975,6 +1975,7 @@ void target_execute_cmd(struct se_cmd *cmd)
}
cmd->t_state = TRANSPORT_PROCESSING;
cmd->transport_state &= ~CMD_T_PRE_EXECUTE;
cmd->transport_state |= CMD_T_ACTIVE | CMD_T_SENT;
spin_unlock_irq(&cmd->t_state_lock);
@ -2667,6 +2668,7 @@ int target_get_sess_cmd(struct se_cmd *se_cmd, bool ack_kref)
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);

1
include/target/target_core_base.h
View file

@ -490,6 +490,7 @@ struct se_cmd {
#define CMD_T_STOP (1 << 5)
#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;