linux-kernel - SCSI reusing tags during error recovery

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [day] [month] [year] [list]

Message-ID: <537305.92125.qm@web31812.mail.mud.yahoo.com>
Date:	Mon, 10 Jan 2011 10:21:16 -0800 (PST)
From:	Luben Tuikov <ltuikov@...oo.com>
To:	linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org,
	James Bottomley <James.Bottomley@...e.de>
Subject: SCSI reusing tags during error recovery

Observed is on the wire, the following scenario:

0: Tag A (READ) -->
  (Times out)
1: Tag X (TMF ABORT TASK, TTBM=A) -->
2: Tag X (TMR FUNCTION COMPLETE) <--
3: Tag A (TUR) -->
4: Tag A (TUR status GOOD) <--
5: Tag A+2 (some command) -->
...

Undoubtedly resulting from the SCSI layer reusing the request
structure of the timed out Tag A to issue the Test Unit Ready
command, sequence 3.

However, if the task manager were unable to abort Tag A and
returned a different task management result, then the TUR would
complete with CHECK CONDITION (ABORTED COMMAND, OVERLAPPED
COMMANDS ATTEMPTED). Not all transports require the task router
to implement overlapped tag checking, and in most it is optional.
The TUR should go out with Tag A+1.

The SCSI layer should ideally, not perform error recovery ("error
handling" to use Linux' own terminology) on behalf of a timed out
request, but allow higher layers to issue TMF only based on a
ITLQ (tag, a number) or ITL (LUN, a structure) or IT nexus
(target port).

A previous issue I raised, tag generation for tags of task
management functions, can be found here:
http://marc.info/?l=linux-scsi&m=128902337522890&w=2

   Luben

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/