linux-kernel - [PATCH v5 2/2] blk-zoned: allow BLKREPORTZONE without CAP_SYS

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Date:   Wed, 11 Aug 2021 11:05:19 +0000
From:   Niklas Cassel <Niklas.Cassel@....com>
To:     Jens Axboe <axboe@...nel.dk>, Hannes Reinecke <hare@...e.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        Damien Le Moal <Damien.LeMoal@....com>,
        Shaun Tancheff <shaun@...cheff.com>
CC:     Damien Le Moal <Damien.LeMoal@....com>,
        Niklas Cassel <Niklas.Cassel@....com>,
        Aravind Ramesh <Aravind.Ramesh@....com>,
        Adam Manzanares <a.manzanares@...sung.com>,
        Himanshu Madhani <himanshu.madhani@...cle.com>,
        Johannes Thumshirn <Johannes.Thumshirn@....com>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>,
        Jens Axboe <axboe@...com>,
        "linux-block@...r.kernel.org" <linux-block@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: [PATCH v5 2/2] blk-zoned: allow BLKREPORTZONE without CAP_SYS_ADMIN

From: Niklas Cassel <niklas.cassel@....com>

A user space process should not need the CAP_SYS_ADMIN capability set
in order to perform a BLKREPORTZONE ioctl.

Getting the zone report is required in order to get the write pointer.
Neither read() nor write() requires CAP_SYS_ADMIN, so it is reasonable
that a user space process that can read/write from/to the device, also
can get the write pointer. (Since e.g. writes have to be at the write
pointer.)

Fixes: 3ed05a987e0f ("blk-zoned: implement ioctls")
Signed-off-by: Niklas Cassel <niklas.cassel@....com>
Reviewed-by: Damien Le Moal <damien.lemoal@....com>
Reviewed-by: Aravind Ramesh <aravind.ramesh@....com>
Reviewed-by: Adam Manzanares <a.manzanares@...sung.com>
Reviewed-by: Himanshu Madhani <himanshu.madhani@...cle.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@....com>
Cc: stable@...r.kernel.org # v4.10+
---
Changes since v4:
-Picked up additional Reviewed-by tag.
-Corrected Damien's email.

 block/blk-zoned.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/block/blk-zoned.c b/block/blk-zoned.c
index 8a60dbeb44be..1d0c76c18fc5 100644
--- a/block/blk-zoned.c
+++ b/block/blk-zoned.c
@@ -360,9 +360,6 @@ int blkdev_report_zones_ioctl(struct block_device *bdev, fmode_t mode,
 	if (!blk_queue_is_zoned(q))
 		return -ENOTTY;
 
-	if (!capable(CAP_SYS_ADMIN))
-		return -EACCES;
-
 	if (copy_from_user(&rep, argp, sizeof(struct blk_zone_report)))
 		return -EFAULT;
 
-- 
2.31.1