blk-zoned: allow zone management send operations without CAP_SYS_ADMIN

Zone management send operations (BLKRESETZONE, BLKOPENZONE, BLKCLOSEZONE
and BLKFINISHZONE) should be allowed under the same permissions as write().
(write() does not require CAP_SYS_ADMIN).

Additionally, other ioctls like BLKSECDISCARD and BLKZEROOUT only check if
the fd was successfully opened with FMODE_WRITE.
(They do not require CAP_SYS_ADMIN).

Currently, zone management send operations require both CAP_SYS_ADMIN
and that the fd was successfully opened with FMODE_WRITE.

Remove the CAP_SYS_ADMIN requirement, so that zone management send
operations match the access control requirement of write(), BLKSECDISCARD
and BLKZEROOUT.

Fixes: 3ed05a9 ("blk-zoned: implement ioctls")
Signed-off-by: Niklas Cassel <[email protected]>
Reviewed-by: Damien Le Moal <[email protected]>
Reviewed-by: Aravind Ramesh <[email protected]>
Reviewed-by: Adam Manzanares <[email protected]>
Reviewed-by: Himanshu Madhani <[email protected]>
Reviewed-by: Johannes Thumshirn <[email protected]>
Cc: [email protected] # v4.10+
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jens Axboe <[email protected]>

Author: Niklas Cassel

block/blk-zoned.c

@@ -421,9 +421,6 @@ int blkdev_zone_mgmt_ioctl(struct block_device *bdev, fmode_t mode,
 	if (!blk_queue_is_zoned(q))
 		return -ENOTTY;
 
-	if (!capable(CAP_SYS_ADMIN))
-		return -EACCES;
-
 	if (!(mode & FMODE_WRITE))
 		return -EBADF;