3.16.54-rc1 review patch. If anyone has any objections, please let me know.
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From: Nicholas Bellinger nab@linux-iscsi.org
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@datera.io Cc: Donald White dew@datera.io Cc: Mike Christie mchristi@redhat.com Cc: Hannes Reinecke hare@suse.com Signed-off-by: Nicholas Bellinger nab@linux-iscsi.org [bwh: Backported to 3.16: - Use target_core_fabric_ops::get_task_tag to get the tag and %u to format it - Adjust context] Signed-off-by: Ben Hutchings ben@decadent.org.uk --- 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 @@ -141,6 +141,16 @@ 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: %u early failure" + " status: 0x%02x\n", + se_cmd->se_tfo->get_task_tag(se_cmd), + 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: %u already shutdown," " skipping\n", se_cmd->se_tfo->get_task_tag(se_cmd)); --- a/drivers/target/target_core_transport.c +++ b/drivers/target/target_core_transport.c @@ -1797,6 +1797,7 @@ 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); /* @@ -2441,6 +2442,7 @@ int target_get_sess_cmd(struct se_sessio 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 @@ -536,6 +536,7 @@ 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 completion t_transport_stop_comp;