[3.8.y.z extended stable] Patch "esp_scsi: Fix tag state corruption when autosensing." has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    esp_scsi: Fix tag state corruption when autosensing.

to the linux-3.8.y-queue branch of the 3.8.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.8.y-queue

This patch is scheduled to be released in version 3.8.13.12.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.8.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From 05a61bbc25fd195409e91c2876df4360e34ad9d9 Mon Sep 17 00:00:00 2001
From: "David S. Miller" <davem at davemloft.net>
Date: Thu, 1 Aug 2013 18:08:34 -0700
Subject: esp_scsi: Fix tag state corruption when autosensing.

[ Upstream commit 21af8107f27878813d0364733c0b08813c2c192a ]

Meelis Roos reports a crash in esp_free_lun_tag() in the presense
of a disk which has died.

The issue is that when we issue an autosense command, we do so by
hijacking the original command that caused the check-condition.

When we do so we clear out the ent->tag[] array when we issue it via
find_and_prep_issuable_command().  This is so that the autosense
command is forced to be issued non-tagged.

That is problematic, because it is the value of ent->tag[] which
determines whether we issued the original scsi command as tagged
vs. non-tagged (see esp_alloc_lun_tag()).

And that, in turn, is what trips up the sanity checks in
esp_free_lun_tag().  That function needs the original ->tag[] values
in order to free up the tag slot properly.

Fix this by remembering the original command's tag values, and
having esp_alloc_lun_tag() and esp_free_lun_tag() use them.

Reported-by: Meelis Roos <mroos at linux.ee>
Tested-by: Meelis Roos <mroos at linux.ee>
Signed-off-by: David S. Miller <davem at davemloft.net>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 drivers/scsi/esp_scsi.c | 14 ++++++++------
 drivers/scsi/esp_scsi.h |  1 +
 2 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/drivers/scsi/esp_scsi.c b/drivers/scsi/esp_scsi.c
index 34552bf..55548dc 100644
--- a/drivers/scsi/esp_scsi.c
+++ b/drivers/scsi/esp_scsi.c
@@ -530,7 +530,7 @@ static int esp_need_to_nego_sync(struct esp_target_data *tp)
 static int esp_alloc_lun_tag(struct esp_cmd_entry *ent,
 			     struct esp_lun_data *lp)
 {
-	if (!ent->tag[0]) {
+	if (!ent->orig_tag[0]) {
 		/* Non-tagged, slot already taken?  */
 		if (lp->non_tagged_cmd)
 			return -EBUSY;
@@ -564,9 +564,9 @@ static int esp_alloc_lun_tag(struct esp_cmd_entry *ent,
 			return -EBUSY;
 	}

-	BUG_ON(lp->tagged_cmds[ent->tag[1]]);
+	BUG_ON(lp->tagged_cmds[ent->orig_tag[1]]);

-	lp->tagged_cmds[ent->tag[1]] = ent;
+	lp->tagged_cmds[ent->orig_tag[1]] = ent;
 	lp->num_tagged++;

 	return 0;
@@ -575,9 +575,9 @@ static int esp_alloc_lun_tag(struct esp_cmd_entry *ent,
 static void esp_free_lun_tag(struct esp_cmd_entry *ent,
 			     struct esp_lun_data *lp)
 {
-	if (ent->tag[0]) {
-		BUG_ON(lp->tagged_cmds[ent->tag[1]] != ent);
-		lp->tagged_cmds[ent->tag[1]] = NULL;
+	if (ent->orig_tag[0]) {
+		BUG_ON(lp->tagged_cmds[ent->orig_tag[1]] != ent);
+		lp->tagged_cmds[ent->orig_tag[1]] = NULL;
 		lp->num_tagged--;
 	} else {
 		BUG_ON(lp->non_tagged_cmd != ent);
@@ -667,6 +667,8 @@ static struct esp_cmd_entry *find_and_prep_issuable_command(struct esp *esp)
 			ent->tag[0] = 0;
 			ent->tag[1] = 0;
 		}
+		ent->orig_tag[0] = ent->tag[0];
+		ent->orig_tag[1] = ent->tag[1];

 		if (esp_alloc_lun_tag(ent, lp) < 0)
 			continue;
diff --git a/drivers/scsi/esp_scsi.h b/drivers/scsi/esp_scsi.h
index 28e22ac..cd68805 100644
--- a/drivers/scsi/esp_scsi.h
+++ b/drivers/scsi/esp_scsi.h
@@ -271,6 +271,7 @@ struct esp_cmd_entry {
 #define ESP_CMD_FLAG_AUTOSENSE	0x04 /* Doing automatic REQUEST_SENSE */

 	u8			tag[2];
+	u8			orig_tag[2];

 	u8			status;
 	u8			message;
--
1.8.1.2