Commit d8855c15 authored Oct 01, 2013 by Nicholas Bellinger

target: Fix recursive COMPARE_AND_WRITE callback failure



This patch addresses a bug when compare_and_write_callback() invoked from
target_complete_ok_work() hits an failure from __target_execute_cmd() ->
cmd->execute_cmd(), that ends up calling transport_generic_request_failure()
-> compare_and_write_post(), thus causing SCF_COMPARE_AND_WRITE_POST to
incorrectly be set.

The result of this bug is that target_complete_ok_work() no longer hits
the if (!rc && !(cmd->se_cmd_flags & SCF_COMPARE_AND_WRITE_POST) check
that forces an immediate return, and instead double completes the se_cmd
in question, triggering an OOPs in the process.

This patch changes compare_and_write_post() to only set this bit when a
failure has not already occured to ensure the immediate return from within
target_complete_ok_work(), and thus allow transport_generic_request_failure()
to handle the sending of the CHECK_CONDITION exception status.

Reported-by: Thomas Glanzmann <thomas@glanzmann.de>
Tested-by: Thomas Glanzmann <thomas@glanzmann.de>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

parent b7191253

drivers/target/target_core_sbc.c

+10 −1

Original line number	Diff line number	Diff line
		@@ -349,7 +349,16 @@ static sense_reason_t compare_and_write_post(struct se_cmd *cmd)
		{
		struct se_device *dev = cmd->se_dev;

		/*
		* Only set SCF_COMPARE_AND_WRITE_POST to force a response fall-through
		* within target_complete_ok_work() if the command was successfully
		* sent to the backend driver.
		*/
		spin_lock_irq(&cmd->t_state_lock);
		if ((cmd->transport_state & CMD_T_SENT) && !cmd->scsi_status)
		cmd->se_cmd_flags \|= SCF_COMPARE_AND_WRITE_POST;
		spin_unlock_irq(&cmd->t_state_lock);

		/*
		* Unlock ->caw_sem originally obtained during sbc_compare_and_write()
		* before the original READ I/O submission.