-----Original Message-----
From: Niklas Cassel <redacted>
Sent: Monday, June 14, 2021 5:53 PM
To: Jens Axboe <axboe@kernel.dk>; Hannes Reinecke <hare@suse.com>; Martin K.
Petersen [off-list ref]; Damien Le Moal
[off-list ref]; Shaun Tancheff [off-list ref]
Cc: Damien Le Moal <redacted>; Niklas Cassel
[off-list ref]; stable@vger.kernel.org; Jens Axboe [off-list ref];
linux-block@vger.kernel.org; linux-kernel@vger.kernel.org
Subject: [PATCH v3 2/2] blk-zoned: allow BLKREPORTZONE without
CAP_SYS_ADMIN

From: Niklas Cassel <redacted>

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 <redacted>
Cc: stable@vger.kernel.org # v4.10+
---
Changes since v2:
-Drop the FMODE_READ check. Right now it is possible to open() the device with
O_WRONLY and get the zone report from that fd. Therefore adding a FMODE_READ
check on BLKREPORTZONE would break existing applications. Instead, just remove
the existing CAP_SYS_ADMIN check.

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

diff --git a/block/blk-zoned.c b/block/blk-zoned.c index

0789e6e9f7db..457eceabed2e 100644

--- a/block/blk-zoned.c
+++ b/block/blk-zoned.c

@@ -288,9 +288,6 @@ 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