linux-kernel - Userspace regression with 6baca7601bde ("scsi: target: drop unused pi_prot

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Message-ID: <57120b72-2ab9-bfa5-f69c-31aee78d5936@redhat.com>
Date:   Sun, 3 Feb 2019 17:56:00 +0100
From:   Laura Abbott <labbott@...hat.com>
To:     David Disseldorp <ddiss@...e.de>, Christoph Hellwig <hch@....de>,
        "Martin K. Petersen" <martin.petersen@...cle.com>
Cc:     "Nicholas A. Bellinger" <nab@...ux-iscsi.org>,
        linux-scsi@...r.kernel.org, target-devel@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Userspace regression with 6baca7601bde ("scsi: target: drop unused
 pi_prot_format attribute storage")

Hi,

Fedora got a bug report of a new permission denied error with 5.0-rc2:

>   File "/usr/lib/python3.7/site-packages/rtslib_fb/utils.py", line 100, in fread
>     with open(path, 'r') as file_fd:
> PermissionError: [Errno 13] Permission denied: '/sys/kernel/config/target/core/fileio_28/xxx/attrib/pi_prot_format'

This looks like an intentional behavior change with

commit 6baca7601bdee2e57f20c45d63eb53b89b33e816
Author: David Disseldorp <ddiss@...e.de>
Date:   Fri Nov 23 18:36:11 2018 +0100

     scsi: target: drop unused pi_prot_format attribute storage
     
     On write, the pi_prot_format configfs attribute invokes the device
     format_prot() callback if present. Read dumps the contents of
     se_dev_attrib.pi_prot_format which is always zero.  Make the configfs
     attribute write-only, and drop the always zero se_dev_attrib.pi_prot_format
     storage.
     
     Signed-off-by: David Disseldorp <ddiss@...e.de>
     Reviewed-by: Christoph Hellwig <hch@....de>
     Signed-off-by: Martin K. Petersen <martin.petersen@...cle.com>


Unfortunately, existing code that's opening with read permissions is now broken.
Can this be reverted? Full bug at https://bugzilla.redhat.com/show_bug.cgi?id=1667505

Thanks,
Laura