Patch "Revert "target: Fix residual overflow handling in target_complete_cmd_with_length"" has been added to the 4.8-stable tree

This is a note to let you know that I've just added the patch titled

Revert "target: Fix residual overflow handling in target_complete_cmd_with_length"

to the 4.8-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:
revert-target-fix-residual-overflow-handling-in-target_complete_cmd_with_length.patch
and it can be found in the queue-4.8 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Nicholas Bellinger <[email protected]>
Date: Sun, 16 Oct 2016 00:27:42 -0700
Subject: Revert "target: Fix residual overflow handling in target_complete_cmd_with_length"

From: Nicholas Bellinger <[email protected]>

commit 61f36166c245e563c7a2b624f4c78c5ce0f680d6 upstream.

This reverts commit c1ccbfe0311e2380a6d2dcb0714b36904f5d586f.

Reverting this patch, as it incorrectly assumes the additional length for INQUIRY in target_complete_cmd_with_length() is SCSI allocation length, which breaks existing user-space code when SCSI allocation length is smaller than additional length.

  root@scsi-mq:~# sg_inq --len=4 -vvvv /dev/sdb
  found bsg_major=253
  open /dev/sdb with flags=0x800
      inquiry cdb: 12 00 00 00 04 00
        duration=0 ms
      inquiry: pass-through requested 4 bytes (data-in) but got -28 bytes
      inquiry: pass-through can't get negative bytes, say it got none
      inquiry: got too few bytes (0)
  INQUIRY resid (32) should never exceed requested len=4
      inquiry: failed requesting 4 byte response: Malformed response to
               SCSI command [resid=32]

AFAICT the original change was not to address a specific host issue, so go ahead and revert to original logic for now.

---
 drivers/target/target_core_transport.c |   16 +---------------
 1 file changed, 1 insertion(+), 15 deletions(-)

@@ -754,15 +754,7 @@ EXPORT_SYMBOL(target_complete_cmd);
 
 void target_complete_cmd_with_length(struct se_cmd *cmd, u8 scsi_status, int length)
 {
-	if (scsi_status != SAM_STAT_GOOD) {
-		return;
-	}
-
-	/*
-	 * Calculate new residual count based upon length of SCSI data
-	 * transferred.
-	 */
-	if (length < cmd->data_length) {
+	if (scsi_status == SAM_STAT_GOOD && length < cmd->data_length) {
 		if (cmd->se_cmd_flags & SCF_UNDERFLOW_BIT) {
 			cmd->residual_count += cmd->data_length - length;
 		} else {

@@ -771,12 +763,6 @@ void target_complete_cmd_with_length(str
 		}
 
 		cmd->data_length = length;
-	} else if (length > cmd->data_length) {
-		cmd->se_cmd_flags |= SCF_OVERFLOW_BIT;
-		cmd->residual_count = length - cmd->data_length;
-	} else {
-		cmd->se_cmd_flags &= ~(SCF_OVERFLOW_BIT | SCF_UNDERFLOW_BIT);
-		cmd->residual_count = 0;
 	}
 
 	target_complete_cmd(cmd, scsi_status);

Patches currently in stable-queue which might be from [email protected] are

queue-4.8/target-re-add-missing-scf_ack_kref-assignment-in-v4.1.y.patch queue-4.8/target-don-t-override-extended_copy-xcopy_pt_cmd-scsi-status-code.patch queue-4.8/target-tcm_fc-use-cpu-affinity-for-responses.patch queue-4.8/target-make-extended_copy-0xe4-failure-return-copy-target-device-not-reachable.patch queue-4.8/revert-target-fix-residual-overflow-handling-in-target_complete_cmd_with_length.patch